1
|
Harlan SS, Philpott CD, Keegan SP, Droege ME, Karve AS, Foreman B, Wakefield D, Mueller EW, Sangha K, Ngwenya LB, Courter JD, Desai P, Droege C. Pharmacokinetics of Levetiracetam Seizure Prophylaxis in Severe Traumatic Brain Injury. Ann Pharmacother 2024; 58:705-714. [PMID: 37776163 DOI: 10.1177/10600280231202246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/01/2023] Open
Abstract
BACKGROUND Drug pharmacokinetics (PK) are altered in neurocritically ill patients, and optimal levetiracetam dosing for seizure prophylaxis is unknown. OBJECTIVE This study evaluates levetiracetam PK in critically ill patients with severe traumatic brain injury (sTBI) receiving intravenous levetiracetam 1000 mg every 8 (LEV8) to 12 (LEV12) hours for seizure prophylaxis. METHODS This prospective, open-label study was conducted at a level 1 trauma, academic, quaternary care center. Patients with sTBI receiving seizure prophylaxis with LEV8 or LEV12 were eligible for enrollment. Five sequential, steady-state, postdose serum levetiracetam concentrations were obtained. Non-compartmental analysis (NCA) and compartmental approaches were employed for estimating pharmacokinetic parameters and projecting steady-state trough concentrations. Pharmacokinetic parameters were compared between LEV8 and LEV12 patients. Monte Carlo simulations (MCS) were performed to determine probability of target trough attainment (PTA) of 6 to 20 mg/L. A secondary analysis evaluated PTA for weight-tiered levetiracetam dosing. RESULTS Ten male patients (5 LEV8; 5 LEV12) were included. The NCA-based systemic clearance and elimination half-life were 5.3 ± 1.2 L/h and 4.8 ± 0.64 hours. A one-compartment model provided a higher steady-state trough concentration for the LEV8 group compared with the LEV12 group (13.7 ± 4.3 mg/L vs 6.3 ± 1.7 mg/L; P = 0.008). Monte Carlo simulations predicted regimens of 500 mg every 6 hours, 1000 mg every 8 hours, and 2000 mg every 12 hours achieved therapeutic target attainment. Weight-tiered dosing regimens achieved therapeutic target attainment using a 75 kg breakpoint. CONCLUSION AND RELEVANCE Neurocritically ill patients exhibit rapid levetiracetam clearance resulting in a short elimination half-life. Findings of this study suggest regimens of levetiracetam 500 mg every 6 hours, 1000 mg every 8 hours, or 2000 mg every 12 hours may be required for optimal therapeutic target attainment. Patient weight of 75 kg may serve as a breakpoint for weight-guided dosing to optimize levetiracetam therapeutic target attainment for seizure prophylaxis.
Collapse
Affiliation(s)
- Sarah Schuman Harlan
- Department of Pharmacy Services, Baptist Memorial Hospital, Memphis, TN, USA
- Department of Clinical Pharmacy and Translational Science, University of Tennessee College of Pharmacy, Memphis, TN, USA
| | - Carolyn D Philpott
- Department of Pharmacy Services, UC Health-University of Cincinnati Medical Center, Cincinnati, OH, USA
- Division of Pharmacy Practice & Administrative Sciences, James L Winkle College of Pharmacy, University of Cincinnati, Cincinnati, OH, USA
| | | | - Molly E Droege
- Department of Pharmacy Services, UC Health-University of Cincinnati Medical Center, Cincinnati, OH, USA
- Division of Pharmacy Practice & Administrative Sciences, James L Winkle College of Pharmacy, University of Cincinnati, Cincinnati, OH, USA
| | - Aniruddha S Karve
- Division of Pharmaceutical Sciences, James L Winkle College of Pharmacy, University of Cincinnati, Cincinnati, OH, USA
| | - Brandon Foreman
- Division of Neurocritical Care, Department of Neurology and Rehabilitation Medicine, College of Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Devin Wakefield
- Division of Trauma and Surgical Critical Care, Department of Surgery, College of Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Eric W Mueller
- Department of Pharmacy Services, UC Health-University of Cincinnati Medical Center, Cincinnati, OH, USA
- Division of Pharmacy Practice & Administrative Sciences, James L Winkle College of Pharmacy, University of Cincinnati, Cincinnati, OH, USA
| | - Kiranpal Sangha
- Department of Pharmacy Services, UC Health-University of Cincinnati Medical Center, Cincinnati, OH, USA
- Division of Pharmacy Practice & Administrative Sciences, James L Winkle College of Pharmacy, University of Cincinnati, Cincinnati, OH, USA
- Community of Scholars Faculty, College of Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Laura B Ngwenya
- Department of Neurosurgery, Department of Neurology and Rehabilitation Medicine, College of Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Joshua D Courter
- Department of Pharmacy Services, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Pankaj Desai
- Division of Pharmaceutical Sciences, James L Winkle College of Pharmacy, University of Cincinnati, Cincinnati, OH, USA
| | - Christopher Droege
- Department of Pharmacy Services, UC Health-University of Cincinnati Medical Center, Cincinnati, OH, USA
- Division of Pharmacy Practice & Administrative Sciences, James L Winkle College of Pharmacy, University of Cincinnati, Cincinnati, OH, USA
| |
Collapse
|
2
|
Chen JL, Kuo CC. Inhibition of resurgent Na + currents by rufinamide. Neuropharmacology 2024; 247:109835. [PMID: 38228283 DOI: 10.1016/j.neuropharm.2024.109835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 12/29/2023] [Accepted: 12/31/2023] [Indexed: 01/18/2024]
Abstract
Na+ channels are essential for the genesis of action potentials in most neurons. After opening by membrane depolarization, Na+ channels enter a series of inactivated states (e.g. the fast, intermediate, and slow inactivated states; or If, Ii, and Is). The inactivated Na+ channel may recover via the open state upon membrane repolarization, giving rise to "resurgent" Na+ currents which could be critical for densely repetitive or burst discharges. We incubated CHO-K1 cells transfected with human NaV1.7 cDNA and measured resurgent currents with whole-cell patch recordings. We found Ii is the major inactivated state responsible for the genesis of resurgent currents. Rufinamide, in therapeutic concentrations, could selectively bind to Ii to slow the recovery process and dose-dependently inhibit resurgent currents. The other Na+ channel-inhibiting antiseizure medications (ASM), such as phenytoin and lacosamide (selectively binds to If and Is, separately), fail to show a similar inhibitory effect in clinically relevant concentrations. Resurgent currents are decreased with lengthening of the prepulse, presumably because of redistribution of the channel from Ii to If. Rufinamide could accentuate the decrease to mimic a use-dependent inhibitory effect. The molecular action of slowing of recovery from inactivation by binding to Ii also explains the highly correlative inhibitory effect of rufinamide on both transient and resurgent Na+ currents. The modest but correlative inhibition of both currents may make a novel synergistic effect and thus strong-enough suppression of pathological repetitive and especially burst discharges. Rufinamide may thus have a unique spectrum of therapeutic applications for disorders with excessive neural excitabilities.
Collapse
Affiliation(s)
- Jian-Lin Chen
- Department of Physiology, National Taiwan University College of Medicine, Taipei, Taiwan.
| | - Chung-Chin Kuo
- Department of Physiology, National Taiwan University College of Medicine, Taipei, Taiwan; Department of Neurology, National Taiwan University Hospital, Taipei, Taiwan.
| |
Collapse
|
3
|
Webb AJ, Avramovska S, Qualls S, Lo CK, Roberts RJ, Barra ME. Impact of an enteral nutrition holding guideline on daily nutrition goals in patients taking phenytoin. Nutr Clin Pract 2023; 38:1334-1342. [PMID: 37537901 DOI: 10.1002/ncp.11051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 06/26/2023] [Accepted: 07/09/2023] [Indexed: 08/05/2023] Open
Abstract
BACKGROUND Concomitant administration of enteral nutrition (EN) and phenytoin decreases phenytoin absorption. Concerns over impaired nutrition, however, may prevent EN from being held surrounding phenytoin administration. This study aimed to evaluate whether EN holding guidelines impacted nutrition goal achievement in patients taking phenytoin. METHODS Adult patients administered enteral phenytoin for acute or chronic seizures while receiving EN during a neurocritical care admission 6 months before and after EN holding guideline implementation were eligible. Patients without phenytoin concentrations or a clinical registered dietitian assessment were excluded. The primary outcome was the percentage of nutrition daily goals attained before and after implementation. Secondary end points included the incidence of hypoglycemia, differences in measured phenytoin concentrations, and rates of therapeutic (10-20 mcg/ml) and high-therapeutic (15-20 mcg/ml) concentration attainment. Concentrations were adjusted for hypoalbuminemia using the Winter-Tozer equation. RESULTS Fifty-five patients representing 412 patient days and 1110 phenytoin administrations were included with 29 preimplementation and 26 postimplementation patients. Median percent attainment of daily EN goals was consistent preimplementation and postimplementation (86% vs 83%, P = 0.48). No significant change in rates of days with hypoglycemia was observed. Adjusted phenytoin concentrations were similar before and after implementation (14.1 vs 15.2 mcg/ml, P = 0.45), but the preimplementation cohort had a lower proportion of high-therapeutic concentrations (23% vs 36%, P = 0.018). CONCLUSION Holding EN for phenytoin did not impact attainment of daily nutrition goals and was not associated with increased rates of hypoglycemia. This is the first study to evaluate the effect of EN holding on nutrition goals in patients receiving phenytoin.
Collapse
Affiliation(s)
- Andrew J Webb
- Department of Pharmacy, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Simona Avramovska
- Department of Pharmacy, Massachusetts General Hospital, Boston, Massachusetts, USA
- Department of Pharmacy, Tufts University Medical Center, Boston, Massachusetts, USA
| | - Stephanie Qualls
- Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Carmen Kaman Lo
- Department of Nutrition and Food Services, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Russel J Roberts
- Department of Pharmacy, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Megan E Barra
- Department of Pharmacy, Massachusetts General Hospital, Boston, Massachusetts, USA
| |
Collapse
|
4
|
Das S, Samajdar SS, Mukherjee S, Sarkar S, Sen S, Pathak A, Lundborg CS, Selvarajan S, Tripathi SK, Pal J, Chatterjee N, Joshi SR. Ten clinical pharmacological interventions in routine care to ensure better treatment outcomes. INTERNATIONAL JOURNAL OF PHARMACY PRACTICE 2023:7146135. [PMID: 37105526 DOI: 10.1093/ijpp/riad032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Affiliation(s)
- Saibal Das
- Indian Council of Medical Research, Centre for Ageing and Mental Health, Kolkata, India
- Department of Global Public Health, Karolinska Institutet, Stockholm, Sweden
| | - Shambo Samrat Samajdar
- Department of Clinical and Experimental Pharmacology, Calcutta School of Tropical Medicine, Kolkata, India
| | - Shatavisa Mukherjee
- Department of Clinical and Experimental Pharmacology, Calcutta School of Tropical Medicine, Kolkata, India
| | - Sougata Sarkar
- Department of Clinical and Experimental Pharmacology, Calcutta School of Tropical Medicine, Kolkata, India
| | - Sumalya Sen
- Department of Clinical and Experimental Pharmacology, Calcutta School of Tropical Medicine, Kolkata, India
| | - Ashish Pathak
- Department of Global Public Health, Karolinska Institutet, Stockholm, Sweden
- Department of Pediatrics, RD Gardi Medical College, Ujjain, India
| | | | - Sandhiya Selvarajan
- Department of Clinical Pharmacology, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India
| | | | - Jyotirmoy Pal
- Department of Medicine, RG Kar College and Hospital, Kolkata, India
| | - Nandini Chatterjee
- Department of Medicine, Institute of Postgraduate Medical Education and Research and SSKM Hospital, Kolkata, India
| | | |
Collapse
|
5
|
Optimizing Status Epilepticus Management in the Emergency Department: It's About Time. Adv Emerg Nurs J 2023; 45:11-22. [PMID: 36757741 DOI: 10.1097/tme.0000000000000440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Status epilepticus (SE) is a frequent medical emergency that requires expedited treatment to avoid the ensuing high incidence of morbidity and mortality associated with prolonged seizures. Protracted seizure duration itself has the potential to result in maladaptive neuronal responses that can not only further increase seizure duration and worsen clinical outcomes but also lead to reduced responsiveness to pharmacotherapy. Benzodiazepines are consistently recommended as first-line treatment due to their rapid onset and efficacy in terminating seizures, followed by the emergent administration of an antiepileptic drug (AED). Various benzodiazepine and AED options are recommended and can be utilized in this setting, all with their own unique advantages and challenges. With time at a premium, agents should be selected that can be rapidly administered and have an advantageous pharmacokinetic profile in order to limit seizure duration and optimize outcomes. The intent of this review is to provide an outline of the importance of time-to-treatment implementation in this setting, assess the landscape of options that may provide timing advantages, and examine potential strategies for deploying expeditious therapy.
Collapse
|
6
|
Singu BS, Morrison H, Irengeya L, Verbeeck RK. Therapeutic drug monitoring of phenytoin and valproic acid in critically ill patients at Windhoek Central Hospital, Namibia. Afr J Lab Med 2022; 11:1628. [PMID: 35937763 PMCID: PMC9350491 DOI: 10.4102/ajlm.v11i1.1628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Accepted: 04/14/2022] [Indexed: 11/19/2022] Open
Abstract
Background Phenytoin and valproic acid, anticonvulsants, have a low therapeutic index and are highly plasma protein bound, mainly to albumin. Hypoalbuminaemia is common in critically ill patients and increases the unbound drug concentration. Thus, monitoring unbound rather than total plasma drug concentrations is recommended to optimise the dosing of these drugs. Objective This retrospective study determined unbound plasma concentrations of phenytoin and valproic as a more accurate value of drug levels than total plasma drug concentrations. Methods Total plasma concentrations were retrieved for 56 Intensive Care Unit patients for phenytoin and 93 for valproic acid. Total drug concentrations were converted to unbound concentrations using a serum albumin-based normalising equation. Results Total phenytoin plasma concentration was below (41.1% of patients), within (46.4%) or above (12.5%) the therapeutic range (10 μg/mL – 20 μg/mL). However, the predicted unbound plasma concentration of phenytoin was above the therapeutic range (1 μg/mL – 2 μg/mL) in the majority of patients (57.1%). For valproic acid, the total plasma concentration of most patients (87.1%) was below the therapeutic range (50 μg/mL – 100 μg/mL); among remaining patients (12.9%), it was within the therapeutic range. In the majority of patients (91.4%), the predicted unbound plasma concentration of valproic acid was between 2.5 μg/mL and 20 μg/mL. Conclusion The usefulness of monitoring the total phenytoin or valproic acid levels for dose optimisation is limited as it is an inaccurate indicator of a patient’s drug therapeutic state. Thus, the unbound plasma drug concentrations should be quantified experimentally or predicted in resource-limited settings.
Collapse
Affiliation(s)
- Bonifasius S Singu
- School of Pharmacy, Faculty of Health Sciences, University of Namibia, Windhoek, Namibia
| | - Helen Morrison
- School of Pharmacy, Faculty of Health Sciences, University of Namibia, Windhoek, Namibia
| | - Lydia Irengeya
- School of Pharmacy, Faculty of Health Sciences, University of Namibia, Windhoek, Namibia
| | - Roger K Verbeeck
- School of Pharmacy, Faculty of Health Sciences, University of Namibia, Windhoek, Namibia
| |
Collapse
|
7
|
Wilfred PM, Mathew S, Chacko B, Prabha R, Mathew BS. Estimation of Free Phenytoin Concentration in Critically Ill Patients with Hypoalbuminemia: Direct Measurement vs Traditional Equations. Indian J Crit Care Med 2022; 26:682-687. [PMID: 35836626 PMCID: PMC9237157 DOI: 10.5005/jp-journals-10071-24235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Background In critically ill patients with low albumin, dose individualization of phenytoin is a challenge. The currently used Sheiner–Tozer equation does not accurately predict the free phenytoin concentration in serum and can result in incorrect dose modifications. The best measure to advocate in these patients is the direct-measurement of free phenytoin concentration. Aims and objectives Phenytoin exhibits complex pharmacokinetics, requiring careful therapeutic drug monitoring. This study aimed to compare the accuracy of the established Sheiner–Tozer calculation method against the direct-measurement of free phenytoin concentration in serum by high performance liquid chromatography in critically ill patients with low albumin. Materials and methods Blood specimens for direct-measurement of both total and free phenytoin concentration were obtained from 57 patients with hypoalbuminemia monitored in the intensive care unit. Results The median [inter-quartile range (IQR)] for Sheiner–Tozer equation calculated total phenytoin concentration and direct-measured total was 17.14 (10.63–24.53) and 9.82 (6.02–13.85) μg mL−1, respectively. Approximately 53 and 5% of patients were found to be subtherapeutic and supratherapeutic for direct-measured total phenytoin concentrations, respectively. In contrast, on applying the Sheiner–Tozer calculation, 23 and 40% had subtherapeutic and supratherapeutic concentrations, respectively, for total phenytoin concentration. The median (IQR) for direct-measured, routine and Sheiner–Tozer equation calculated free phenytoin concentration were 1.92 (1.06–2.76), 0.98 (0.60–1.39), and 1.71 (1.06–2.45) μg mL−1, respectively. Only 45.7% of patients were in agreement with respect to the therapeutic category when direct-measured free was compared against routine calculation free. Conclusion In patients with low albumin, free phenytoin concentration based on the Sheiner–Tozer corrected equation accurately classified patients based on their therapeutic category of free phenytoin in 73.7% of patients. Hence, for individualization of phenytoin dosage in critically ill patients with low albumin, we recommend direct-measurement of free phenytoin concentration. How to cite this article Wilfred PM, Mathew S, Chacko B, Prabha R, Mathew BS. Estimation of Free Phenytoin Concentration in Critically Ill Patients with Hypoalbuminemia: Direct-measurement vs Traditional Equations. Indian J Crit Care Med 2022;26(6):682–687.
Collapse
Affiliation(s)
- Premila M Wilfred
- Department of Pharmacology and Clinical Pharmacology, Christian Medical College and Hospital, Vellore, Tamil Nadu, India
| | - Sumith Mathew
- Department of Pharmacology and Clinical Pharmacology, Christian Medical College and Hospital, Vellore, Tamil Nadu, India
| | - Binila Chacko
- Medical Intensive Care Unit, Christian Medical College and Hospital, Vellore, Tamil Nadu, India
| | - Ratna Prabha
- Department of Pharmacology and Clinical Pharmacology, Christian Medical College and Hospital, Vellore, Tamil Nadu, India
| | - Binu Susan Mathew
- Department of Pharmacology and Clinical Pharmacology, Christian Medical College and Hospital, Vellore, Tamil Nadu, India
- Binu Susan Mathew, Department of Pharmacology and Clinical Pharmacology, Christian Medical College and Hospital, Vellore, Tamil Nadu, India, Phone: +91 04162282721, e-mail:
| |
Collapse
|
8
|
Liu J, Zhong J, Yang H, Wang D, Zhang Y, Yang Y, Xing G, Kon V. Biotic Supplements in Patients With Chronic Kidney Disease: Meta-Analysis of Randomized Controlled Trials. J Ren Nutr 2022; 32:10-21. [PMID: 34666930 PMCID: PMC9793596 DOI: 10.1053/j.jrn.2021.08.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 07/01/2021] [Accepted: 08/10/2021] [Indexed: 12/30/2022] Open
Abstract
OBJECTIVE Gut flora imbalance characterizes patients with chronic kidney disease (CKD). Although biotic supplementation has been proposed to lessen inflammation and oxidative stress and, thus, reduce the risk of progressive kidney damage and cardiovascular disease, the effects remain controversial. We conducted a meta-analysis to assess the therapeutic benefits of biotics in CKD. METHODS PubMed, Embase, and Cochrane databases were systematically searched for randomized controlled trials that evaluated any biotic (prebiotic, probiotic, synbiotics) supplements in patients with CKD (CKD, stage 3-4 to end-stage renal disease). Primary endpoints included changes in renal function, markers of inflammation, and oxidative stress. Secondary endpoints included changes in levels of uremic toxins and variations in lipid metabolism. RESULTS Twenty-three eligible studies included 842 participants. In a pooled-analysis, biotics did not change estimated glomerular filtration rate (mean difference [MD] = 0.08, P = .92) or serum albumin (MD = -0.01, P = .86), although prebiotics reduced serum creatinine (standardized mean difference [SMD] = -0.23, P = .009) and blood urea nitrogen (MD = -6.05, P < .00001). Biotics improved total antioxidative capacity (SMD = 0.37, P = .007) and malondialdehyde (SMD = -0.96, P = .006) and reduced the inflammatory marker interleukin-6 (SMD = -0.30, P = .01) although not C-reactive protein (SMD = -0.22, P = .20). Biotic intervention reduced some uremic toxins, including p-cresol sulfate (SMD = -2.18, P < .0001) and indoxyl sulfate (MD = -5.14, P = .0009), which decreased in dialysis-dependent patients. Another toxin, indole-3-acetic acid (MD = -0.22, P = .63), did not change. Lipids were unaffected by biotic intervention (total cholesterol: SMD = -0.01, P = .89; high-density lipoprotein: SMD = -0.08, P = .76; low-density lipoprotein: MD = 3.54, P = .28; triglyceride: MD = -2.26, P = .58). CONCLUSION The results highlight the favorable influence of biotics on circulating markers of creatinine, oxidant stress (malondialdehyde, total antioxidative capacity), inflammation (interleukin-6), and uremic toxins (p-cresol sulfate) in patients with CKD. Biotics did not affect estimated glomerular filtration rate, albumin, indole-3-acetic acid, or lipids in either predialysis or dialysis patients.
Collapse
Affiliation(s)
- Jing Liu
- Department of Nephrology, First Affiliated Hospital of Zhengzhou University, Zhengzhou University Institute of Nephrology, Zhengzhou, China.,Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN
| | - JianYong Zhong
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN.,Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN
| | - HaiChun Yang
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN.,Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN
| | - DongQin Wang
- Dongjing Town Health Service Center, Songjiang District, Shanghai, China
| | - Ying Zhang
- Department of Nephrology, First Affiliated Hospital of Zhengzhou University, Zhengzhou University Institute of Nephrology, Zhengzhou, China
| | - YuMeng Yang
- Department of Nephrology, First Affiliated Hospital of Zhengzhou University, Zhengzhou University Institute of Nephrology, Zhengzhou, China
| | - GuoLan Xing
- Department of Nephrology, First Affiliated Hospital of Zhengzhou University, Zhengzhou University Institute of Nephrology, Zhengzhou, China
| | - Valentina Kon
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN
| |
Collapse
|
9
|
Osborne JC, Brown CS, Peffley ND, Wittwer ED, Yalamuri SM. Phenytoin Pharmacokinetics During Venoarterial Extracorporeal Membrane Oxygenation and Plasma Exchange. Cureus 2021; 13:e17120. [PMID: 34527498 PMCID: PMC8434762 DOI: 10.7759/cureus.17120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/11/2021] [Indexed: 11/05/2022] Open
Abstract
Currently, there is minimal guidance to antiepileptic dose adjustment for a patient requiring either venoarterial (VA) extracorporeal membrane oxygenation (ECMO) or plasma exchange (PLEX) therapy, and to our knowledge, there are rare guidances for a patient requiring both. Given the dangers with non-therapeutic concentrations of phenytoin, it is critical for the intensive care unit (ICU) practitioner to understand how the pharmacokinetic parameters of phenytoin change in critically ill patients requiring extracorporeal support. This case study presents a 41-year-old female transferred to the cardiovascular ICU requiring VA ECMO and PLEX for the treatment of systemic lupus erythematosus (SLE)-induced catastrophic antiphospholipid syndrome (CAPS). Free phenytoin concentrations were measured to assess the removal of phenytoin. There was no significant decrease in the free phenytoin concentrations post-PLEX and while on ECMO. Free phenytoin concentrations are not influenced in the setting of PLEX and while on ECMO.
Collapse
Affiliation(s)
| | - Caitlin S Brown
- Pharmacy and Emergency Medicine, Mayo Clinic, Rochester, USA
| | | | | | | |
Collapse
|
10
|
A Novel Correction Equation Avoids High-Magnitude Errors in Interpreting Therapeutic Drug Monitoring of Phenytoin Among Critically Ill Patients. Ther Drug Monit 2021; 42:617-625. [PMID: 32049893 DOI: 10.1097/ftd.0000000000000739] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Phenytoin has a narrow therapeutic index and the potential of under-treatment or toxicity. Available equations are used to correct for the impact of hypoalbuminemia on unbound (free) phenytoin levels. The authors aimed to determine the accuracy of equations used to estimate free phenytoin in hospitalized patients and assess the impact of using additional clinical data. METHODS Concurrently measured total and free phenytoin levels in hospitalized patients (2014-2018) were retrospectively evaluated, excluding those from patients on renal replacement therapy and valproic acid. Differences between actual and estimated free phenytoin levels by the original (Original WTZ), Anderson-modified, and Kane-modified Winter-Tozer equations were assessed using Pearson correlations and Bland-Altman analysis. Thereafter, a population-derived formula was developed and validated in a testing cohort. RESULTS In the 4-year training cohort (n = 81), the Original WTZ equation had the smallest mean difference of all equations. A higher mean difference [-0.362 mcg/mL (95% CI -0.585 to -0.138) vs. -0.054 mcg/mL (95% CI -0.186 to 0.078)] was observed in intensive care unit (ICU) patients compared with non-ICU patients. A cross-validated multivariable model improved the accuracy of free phenytoin estimation in ICU and non-ICU patients, even in the separate testing cohort (n = 52) with respective mean differences of -0.322 mcg/mL (95% CI -0.545 to -0.098) and -0.025 mcg/mL (95% CI -0.379 to 0.329) and was superior to the Original WTZ [mean difference -0.858 mcg/mL (95% CI -1.069 to -0.647) vs. -0.106 mcg/mL (95% CI -0.362 to 0.151), respectively]. CONCLUSIONS Free phenytoin levels in hospitalized patients cannot be accurately determined using available estimation equations, particularly in critically ill patients. Combining ICU status and other available clinical data can improve therapeutic drug monitoring and prevent high-magnitude errors, particularly when free phenytoin assays are not readily available.
Collapse
|
11
|
Brown G, Jang W, Peets A, Ramanathan K. Phenytoin-Induced Cardiac Conduction Abnormalities. JOURNAL OF CARDIAC CRITICAL CARE TSS 2020. [DOI: 10.1055/s-0040-1718986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
AbstractPhenytoin possesses electrophysiological effects consistent with those of the Vaughan–Williams 1B classification. As such, phenytoin may widen the QRS complex but would not be expected to result in QTc prolongation or ST elevation. The reported case demonstrates these unexpected electrophysiological effects with supratherapeutic concentrations of phenytoin when no other potential cause could be elucidated. No contributing factors present in the case, compared with previously published reports of electrophysiological effects of supratherapeutic phenytoin concentrations, could be elucidated. The report suggests that clinicians should monitor for potential conduction abnormalities in patients with elevated phenytoin concentrations.
Collapse
Affiliation(s)
- Glen Brown
- Pharmacy Department, St. Paul’s Hospital, Vancouver, British Columbia, Canada
| | - Wesley Jang
- Critical Care Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Adam Peets
- Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Krishnan Ramanathan
- Division of Cardiology, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| |
Collapse
|
12
|
Osuntokun OS, Olayiwola G, Atere TG, Adekomi DA, Adedokun KI, Oladokun OO. Hypothalamic-pituitary-testicular axis derangement following chronic phenytoin-levetiracetam adjunctive treatment in male Wistar rats. Andrologia 2020; 52:e13788. [PMID: 33017495 DOI: 10.1111/and.13788] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Revised: 07/08/2020] [Accepted: 07/13/2020] [Indexed: 02/02/2023] Open
Abstract
The effects of phenytoin (PHT), levetiracetam (LEV) or their adjunctive treatment on the hypothalamic-pituitary-testicular axis in male Wistar rats were determined. Twenty-eight male rats (150-180 g) were randomised into four groups (N = 7). Groups I to IV received intraperitoneal treatment of either normal saline (0.2 ml i.p) or PHT (50 mg/kg i.p) or LEV (50 mg/kg) or PHT (25 mg/kg) and LEV (25 mg/kg) combination for 28 days. The organ weight, concentrations of reproductive hormones and semen profile were determined, while the brain, epididymis and testis were preserved in 10% neutral-buffered formalin for the histomorphological study. Data were analysed using descriptive and inferential statistics. The results were presented as mean ± SEM in graphs or tables, while the level of significance was taken at p < .05. The semen profile was altered significantly in all the treatment groups. The gonadotrophic releasing hormone, luteinising hormone and testosterone concentration decreased significantly in the PHT- and PHT + LEV-treated groups compared with control. There were various disruptions in the hypothalamus, pituitary and testis of the PHT- and PHT + LEV adjunctive-treated rats. In conclusion, chronic PHT + LEV treatment may pose deleterious effects on the hypothalamic-pituitary-testicular axis than single treatment of either of the two drugs in male rats.
Collapse
Affiliation(s)
- Opeyemi S Osuntokun
- Department of Physiology, Faculty of Basic Medical Sciences, College of Health Sciences, Osun State University, Osogbo, Nigeria
| | - Gbola Olayiwola
- Department of Clinical Pharmacy and Pharmacy Administration, Faculty of Pharmacy, Obafemi Awolowo University, Ile-Ife, Nigeria
| | - Tope G Atere
- Department of Medical Biochemistry, Faculty of Basic Medical Sciences, College of Health Sciences, Osun State University, Osogbo, Nigeria
| | - Damilare A Adekomi
- Department of Anatomy, Faculty of Basic Medical Sciences, College of Health Sciences, Osun State University, Osogbo, Nigeria
| | - Kabiru I Adedokun
- Department of Physiology, Faculty of Basic Medical Sciences, College of Health Sciences, Osun State University, Osogbo, Nigeria
| | - Olayemi O Oladokun
- Department of Physiology, Faculty of Basic Medical Sciences, College of Health Sciences, Osun State University, Osogbo, Nigeria
| |
Collapse
|
13
|
Noval M, Seung H, Armahizer M. Evaluation of Fosphenytoin Therapeutic Drug Monitoring in the Neurocritical Care Unit. Drugs R D 2020; 20:17-22. [PMID: 31925752 PMCID: PMC7067712 DOI: 10.1007/s40268-019-00292-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVE The aim of this study was to determine whether the current method of calculating a fosphenytoin reloading dose results in a therapeutic free phenytoin level on subsequent days. METHODS Medical records of patients receiving fosphenytoin in the neurocritical care unit between July 2017 and June 2018 were screened. Included patients were those who had received at least three doses of fosphenytoin and required reloading doses according to concentrations obtained through therapeutic drug monitoring. Free phenytoin levels were categorized based on the prespecified patient-specific target range, generally between 1.5 and 2.5 mcg/mL. RESULTS Of the fosphenytoin reloading doses administered, 48% (73/152) resulted in a therapeutic free phenytoin concentration on the subsequent day, with the remaining 52% resulting in nontherapeutic levels (39% subtherapeutic, 13% supratherapeutic). Our evaluation of reloading dose calculation strategies indicated that patients were two times as likely to obtain a therapeutic level when a modified pharmacokinetic equation omitting the use of volume of distribution or salt formulation was used (58%, n = 39) than they were with doses calculated using the current pharmacokinetic model (41%, n = 20) or doses based on provider preference (39%, n = 14). CONCLUSION The current method of calculating a fosphenytoin reloading dose in the critically ill population does not consistently result in therapeutic concentrations. With multiple factors affecting the pharmacokinetics of critically ill patients, the creation of a new pharmacokinetic model with less emphasis on volume of distribution may more consistently result in therapeutic concentrations.
Collapse
Affiliation(s)
- Mandee Noval
- University of Maryland Medical Center, 22 S. Greene Street, Baltimore, MD, USA.
| | - Hyunuk Seung
- University of Maryland School of Pharmacy, 20 N Pine St, Baltimore, MD, USA
| | - Michael Armahizer
- University of Maryland Medical Center, 22 S. Greene Street, Baltimore, MD, USA
| |
Collapse
|
14
|
Seyfinejad B, Khoubnasabjafari M, Ziaei SE, Ozkan SA, Jouyban A. Electromembrane extraction as a new approach for determination of free concentration of phenytoin in plasma using capillary electrophoresis. ACTA ACUST UNITED AC 2020; 28:615-624. [PMID: 32803689 DOI: 10.1007/s40199-020-00366-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Accepted: 08/05/2020] [Indexed: 01/26/2023]
Abstract
PURPOSE Electromembrane extraction is a new membrane-based extraction method in which charged compounds are extracted by an electric field. So far, this method has been used to extract and isolate a variety of acidic and basic drugs from various samples, including blood and plasma. However, in this procedure, it is not yet clear whether only unbound fraction of a drug is extracted or the total drug. The aim of this study is to reveal the nature of drug extraction in the presence of plasma proteins. METHODS To determine the nature of the extraction, the electromembrane extraction was performed from plasma solutions of phenytoin with concentrations 0.03 and 1.0 μg/mL, then the result was compared with the values obtained from the electromembrane extraction of ultrafiltrate of the same solutions (free concentration) and protein-free ultrafiltrate of plasma with final concentration of 0.03 and 1.0 μg/mL (total concentration). For this purpose, EME followed by capillary electrophoresis coupled with diode array detection was optimized and validated. RESULTS The results showed that the electromembrane extraction method was only able to extract the unbound fraction of phenytoin from plasma samples. The method was validated over a concentration range of 0.03-4 μg/mL. The inter and intra-assay precisions were less than 6.7%. The phenytoin protein binding was also determined to be in agreement with the literature data and confirms the validity of this method. CONCLUSION This sensitive and quick EME approach for determining the free concentration of a phenytoin, can be a good alternative to classic methods for therapeutic drug monitoring and pharmacokinetic studies.
Collapse
Affiliation(s)
- Behrouz Seyfinejad
- Pharmaceutical Analysis Research Center and Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran.,Student Research Committee, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Maryam Khoubnasabjafari
- Tuberculosis and Lung Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Saba Eivaz Ziaei
- Neurosciences Research Center, Imam Reza Hospital, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Sibel A Ozkan
- Department of Analytical Chemistry, Faculty of Pharmacy, Ankara University, 06100, Ankara, Turkey
| | - Abolghasem Jouyban
- Pharmaceutical Analysis Research Center and Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran. .,Digestive Diseases Research Institute, Tehran University of Medical Sciences, Tehran, Iran.
| |
Collapse
|
15
|
Chang WC, Hung SI, Carleton BC, Chung WH. An update on CYP2C9 polymorphisms and phenytoin metabolism: implications for adverse effects. Expert Opin Drug Metab Toxicol 2020; 16:723-734. [DOI: 10.1080/17425255.2020.1780209] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Wan-Chun Chang
- Division of Translational Therapeutics, Department of Pediatrics, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
- British Columbia Children’s Hospital Research Institute, Vancouver, British Columbia, Canada
| | - Shuen-Iu Hung
- Department of Dermatology, Drug Hypersensitivity Clinical and Research Center, Chang Gung Memorial Hospital, Linkou, Taipei, Taiwan
- College of Medicine, Chang Gung University, Taoyuan, Taiwan
- Cancer Vaccine and Immune Cell Therapy Core Laboratory, Chang Gung Immunology Consortium, Chang Gung Memorial Hospital, Linkou, Taiwan
- Whole-Genome Research Core Laboratory of Human Diseases, Chang Gung Memorial Hospital, Keelung, Taiwan
| | - Bruce C Carleton
- Division of Translational Therapeutics, Department of Pediatrics, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
- British Columbia Children’s Hospital Research Institute, Vancouver, British Columbia, Canada
- Pharmaceutical Outcomes Programme, BC Children’s Hospital, Vancouver, British Columbia, Canada
| | - Wen-Hung Chung
- Department of Dermatology, Drug Hypersensitivity Clinical and Research Center, Chang Gung Memorial Hospital, Linkou, Taipei, Taiwan
- College of Medicine, Chang Gung University, Taoyuan, Taiwan
- Cancer Vaccine and Immune Cell Therapy Core Laboratory, Chang Gung Immunology Consortium, Chang Gung Memorial Hospital, Linkou, Taiwan
- Whole-Genome Research Core Laboratory of Human Diseases, Chang Gung Memorial Hospital, Keelung, Taiwan
- Department of Dermatology, Xiamen Chang Gung Hospital, Teaching Hospital of School of Medicine, Tsinghua University, China
| |
Collapse
|
16
|
Efficacy, Tolerability and Serum Phenytoin Levels after Intravenous Fosphenytoin Loading Dose in Children with Status Epilepticus. Indian Pediatr 2020. [DOI: 10.1007/s13312-020-1754-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
17
|
Wiebe AZ, Terry K, Skaggs J. Phenytoin Serum Concentrations in Patients With Left Ventricular Support Devices: A Case Series. J Pharm Pract 2019; 34:325-328. [PMID: 31868073 DOI: 10.1177/0897190019894424] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE Achieving therapeutic levels of phenytoin is critical to its efficacy and safety. Free serum levels represent pharmacologically active phenytoin due to the high protein binding of the drug. Predicting free serum levels in patients with left ventricular support devices can be challenging, as the pharmacokinetics (PK) can be significantly altered, and equations to correct total levels have not been validated in this population. The aim of this case series was to describe serum phenytoin concentrations in critically ill patients requiring left ventricular support devices. METHODS A retrospective chart review was performed including patients who received phenytoin therapy and had at least 1 set of simultaneously measured free and total serum phenytoin levels during left ventricular support with a mechanical device. Corrected total phenytoin levels were calculated using Sheiner-Tozer equations. RESULTS Three patients were included in this case series. Patients 1 and 2 required venoarterial extracorporeal membrane oxygenation (ECMO) during phenytoin therapy, and patient 3 had a durable left ventricular assist device (LVAD). Measured phenytoin levels ranged from 4.1 to 11.4 µg/mL, and calculated corrected levels were 6.8 to 18.4. Measured free phenytoin levels ranged from 1.2 to 3.6 µg/mL, which correlated with free fractions of 15.8% to 37.9%. CONCLUSION This case series demonstrates a higher percentage of free phenytoin compared to the total serum level than would be predicted and an inability to rely on corrected total phenytoin level to predict whether it is within therapeutic range. Monitoring of free serum phenytoin concentrations should be strongly considered in critically ill patients requiring LVAD or ECMO support.
Collapse
Affiliation(s)
- Amanda Z Wiebe
- Department of Pharmacy, 114380University of Utah Health, Salt Lake City, UT, USA
| | - Kimberly Terry
- Department of Pharmacy, 114380University of Utah Health, Salt Lake City, UT, USA
| | - John Skaggs
- Department of Anesthesiology, 114380University of Utah Health, Salt Lake City, UT, USA
| |
Collapse
|
18
|
Holder MC, Bailey AM, Baum RA, Justice SB, Weant KA. Assessment of dose capping in phenytoin loading practices in the emergency department and the impact of an emergency medicine pharmacist. JOURNAL OF THE AMERICAN COLLEGE OF CLINICAL PHARMACY 2019. [DOI: 10.1002/jac5.1086] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Martina C. Holder
- Clinical Pharmacy University of Florida Shands Hospital, University of Florida College of Pharmacy Gainesville Florida
| | - Abby M. Bailey
- Clinical Pharmacy University of Kentucky HealthCare Lexington Kentucky
- Department of Pharmacy Services University of Kentucky College of Pharmacy Lexington Kentucky
- Department of Pharmacy Practice and Science University of Kentucky College of Pharmacy Lexington Kentucky
| | - Regan A. Baum
- Clinical Pharmacy University of Kentucky HealthCare Lexington Kentucky
- Department of Pharmacy Services University of Kentucky College of Pharmacy Lexington Kentucky
- Department of Pharmacy Practice and Science University of Kentucky College of Pharmacy Lexington Kentucky
| | | | - Kyle A. Weant
- Clinical Pharmacy Medical University of South Carolina College of Pharmacy, Medical University of South Carolina Charleston South Carolina
| |
Collapse
|
19
|
Khoubnasabjafari M, Samadi A, Jouyban A. In-situ microscale spectrophotometric determination of phenytoin by using branched gold nanoparticles. Mikrochim Acta 2019; 186:422. [PMID: 31187298 DOI: 10.1007/s00604-019-3546-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 05/22/2019] [Indexed: 01/20/2023]
Abstract
A rapid method for the sensitive detection of phenytoin (PHT) by branched gold nanoparticles (B-AuNPs) is described. These nanoparticles were synthesized by adding methanol as the reducing agent and poly(ethylene glycol) as the stabilizer at 70 °C. The B-AuNPs are red in color with an absorption maximum at 540 nm when prepared in situ. However, the color becomes increasingly weaker when PHT is present in increasing concentrations. This method can determine PHT over the 67-670 ng·mL-1 concentration range, with detection limit of 21 ng·mL-1. The relative standard deviation for five replicate measurements at 68 and 530 ng·mL-1 of PHT was 3.2% and 1.2%, respectively. The method was applied to the determination of PHT in plasma samples of epileptic patients, and the results were in agreement with those obtained by a standard official method. Graphical abstract Branched gold nanoparticles (AuNPs) prepared in situ have a red color with an absorption maximum at 540 nm. The color becomes increasingly weaker with decreasing the intensity of the characteristic SPR band when PHT is present in increasing concentration. The current assay is capable of determining PHT over the 67-670 ng·mL-1 concentration range with a limit of detection of 21 ng·mL-1.
Collapse
Affiliation(s)
- Maryam Khoubnasabjafari
- Tuberculosis and Lung Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, 51656-65811, Iran
| | - Azam Samadi
- Pharmaceutical Analysis Research Center and Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, 51656-65811, Iran.
| | - Abolghasem Jouyban
- Pharmaceutical Analysis Research Center and Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, 51656-65811, Iran.,Kimia Idea Pardaz Azarbayjan (KIPA) Science Based Company, Tabriz University of Medical Sciences, Tabriz, 51656-65811, Iran
| |
Collapse
|
20
|
Javadi SS, Mahjub R, Taher A, Mohammadi Y, Mehrpooya M. Correlation between measured and calculated free phenytoin serum concentration in neurointensive care patients with hypoalbuminemia. Clin Pharmacol 2018; 10:183-190. [PMID: 30588130 PMCID: PMC6298392 DOI: 10.2147/cpaa.s186322] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Purpose In critically ill patients, monitoring free phenytoin concentration is a valuable method for phenytoin-dosage adjustment. However, due to technical difficulties and the high cost of these methods, the Sheiner–Tozer equation is routinely used for estimating free phenytoin concentration in clinical practice. There have been conflicting results concerning accuracy and precision of the Sheiner–Tozer equation for prediction of free phenytoin concentration in various patient populations. Therefore, this study was conducted to evaluate the accuracy and correlation of measured and calculated free phenytoin concentrations in neurointensive care patients with hypoalbuminemia. Methods A total of 65 adult neurointensive care patients with hypoalbuminemia who were receiving phenytoin for prevention or treatment of seizures were recruited in this study. In addition to measuring free phenytoin concentration by HPLC, free phenytoin concentration was calculated using both conventional and revised Sheiner–Tozer equations. Eventually, the correlation and level of agreement between measured and calculated free phenytoin concentrations were evaluated. Results The mean albumin concentration of studied patients was 2.63±0.57 g/dL. There was a significant but weak–moderate correlation between measured and calculated free phenytoin concentration using conventional and revised Sheiner–Tozer equations (r=0.45 and r=0.43, respectively). Conventional and revised Sheiner–Tozer equations were not able to predict free phenytoin concentrations accurately in 33.85% and 35.4% of patients, respectively. Although the sex of patients did not have a significant impact on the level of agreement, younger patients had a higher level of agreement. Conclusion Although there was a moderate correlation between calculated and measured free phenytoin concentration, the Sheiner–Tozer equation was not able to predict free phenytoin concentration accurately in all patients, especially in older patients. Therefore, monitoring free phenytoin serum concentration besides clinical outcomes should be considered for phenytoin-dose adjustment in critically ill patients.
Collapse
Affiliation(s)
- Seyyede-Sareh Javadi
- Department of Clinical Pharmacy, School of Pharmacy, Hamadan University of Medical Sciences, Hamadan, Iran,
| | - Reza Mahjub
- Department of Pharmaceutics, School of Pharmacy, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Abbas Taher
- Department of Anesthesiology and Critical Care, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Younes Mohammadi
- Modeling of Noncommunicable Diseases Research Center, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Maryam Mehrpooya
- Department of Clinical Pharmacy, School of Pharmacy, Hamadan University of Medical Sciences, Hamadan, Iran,
| |
Collapse
|
21
|
DasGupta R, Alaniz C, Burghardt D. Evaluation of Intravenous Phenytoin and Fosphenytoin Loading Doses: Influence of Obesity and Sex. Ann Pharmacother 2018; 53:458-463. [PMID: 30522345 DOI: 10.1177/1060028018818785] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Recommended loading doses (LDs) of phenytoin and fosphenytoin range from 10 to 25 mg/kg. Few studies have examined the LD requirements in male versus female patients and in patients who are obese. OBJECTIVES To examine the influence of obesity and sex on phenytoin LDs. METHODS This was a retrospective cohort study comparing free phenytoin or fosphenytoin serum concentrations following LDs in male versus female and nonobese versus obese patients. An equation used for determining LDs in obese patients was evaluated. RESULTS There were 141 nonobese and 54 obese patients. When adjusted for total body weight, the obese cohort received a smaller LD than the nonobese cohort (17 mg/kg, interquartile range [IQR] = 14.9-20.0, vs 20 mg/kg, IQR = 18.6-20.0, respectively; P < 0.001). There was no difference between the 2 cohorts in the measured free phenytoin concentration following the LD (obese: 1.7 µg/mL [IQR = 1.4-2.0]; nonobese: 1.8 µg/mL [IQR = 1.5-2.1]; P = 0.16). In the obese cohort, men received a significantly lower weight-based phenytoin dose compared with women (15 mg/kg [IQR = 14.0-19.2], vs 19.9 mg/kg [IQR = 15.0-20.0], respectively; P = 0.008). Postload free phenytoin concentrations were similar between the 2 groups (male: 1.6 µg/mL [IQR = 1.2-2.1]; female: 1.7 µg/mL [IQR = 1.4-2.0]; P = 0.24). Conclusion and Relevance: Phenytoin and fosphenytoin LDs of at least 15 mg/kg of actual body weight are more likely to lead to desired free phenytoin concentrations. Obese female patients need a larger weight-based dose than male patients to achieve similar postload phenytoin concentrations.
Collapse
Affiliation(s)
| | - Cesar Alaniz
- 2 University of Michigan College of Pharmacy, Ann Arbor, MI, USA.,3 Michigan Medicine, Ann Arbor, MI, USA
| | | |
Collapse
|
22
|
Hösli R, König S, Mühlebach SF. Development and Validation of an LC-MS/MS Method and Comparison with a GC-MS Method to Measure Phenytoin in Human Brain Dialysate, Blood, and Saliva. JOURNAL OF ANALYTICAL METHODS IN CHEMISTRY 2018; 2018:8274131. [PMID: 29805839 PMCID: PMC5901821 DOI: 10.1155/2018/8274131] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 02/07/2018] [Accepted: 02/25/2018] [Indexed: 06/08/2023]
Abstract
Phenytoin (PHT) is one of the most often used critical dose drugs, where insufficient or excessive dosing can have severe consequences such as seizures or toxicity. Thus, the monitoring and precise measuring of PHT concentrations in patients is crucial. This study develops and validates an LC-MS/MS method for the measurement of phenytoin concentrations in different body compartments (i.e., human brain dialysate, blood, and saliva) and compares it with a formerly developed GC-MS method that measures PHT in the same biological matrices. The two methods are evaluated and compared based on their analytical performance, appropriateness to analyze human biological samples, including corresponding extraction and cleanup procedures, and their validation according to ISO 17025/FDA Guidance for Industry. The LC-MS/MS method showed a higher performance compared with the GC-MS method. The LC-MS/MS was more sensitive, needed a smaller sample volume (25 µL) and less chemicals, was less time consuming (cleaning up, sample preparation, and analysis), and resulted in a better LOD (<1 ng/mL)/LOQ (10 ng/mL). The calibration curve of the LC-MS/MS method (10-2000 ng/mL) showed linearity over a larger range with correlation coefficients r2 > 0.995 for all tested matrices (blood, saliva, and dialysate). For larger sample numbers as in pharmacokinetic/pharmacodynamic studies and for bedside as well as routine analyses, the LC-MS/MS method offers significant advantages over the GC-MS method.
Collapse
Affiliation(s)
- Raphael Hösli
- Clinical Pharmacy and Epidemiology, Hospital Pharmacy, University of Basel, Spitalstrasse 26, CH-4031 Basel, Switzerland
- Spitalzentrum Biel, Apotheke, Vogelsang 84, CH-2501 Biel-Bienne, Switzerland
| | - Stefan König
- Division of Forensic Medicine, University of Bern, Bühlstrasse 20, CH-3012 Bern, Switzerland
| | - Stefan F. Mühlebach
- Clinical Pharmacy and Epidemiology, Hospital Pharmacy, University of Basel, Spitalstrasse 26, CH-4031 Basel, Switzerland
| |
Collapse
|
23
|
Matsuyama T, Iwami T, Yamada T, Hayakawa K, Yoshiya K, Irisawa T, Abe Y, Nishimura T, Uejima T, Ohishi Y, Kiguchi T, Kishi M, Kishimoto M, Nakao S, Hayashi Y, Sogabe T, Morooka T, Izawa J, Shimamoto T, Hatakeyama T, Fujii T, Sado J, Kawamura T, Shimazu T, Kitamura T. Prognostic Impact of Serum Albumin Concentration for Neurologically Favorable Outcome in Patients Treated with Targeted Temperature Management After Out-of-Hospital Cardiac Arrest: A Multicenter Prospective Study. Ther Hypothermia Temp Manag 2018; 8:165-172. [PMID: 29364051 DOI: 10.1089/ther.2017.0053] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
To assess whether serum albumin concentration measured upon hospital arrival was useful as an early prognostic biomarker for neurologically favorable outcome in out-of-hospital cardiac arrest (OHCA) patients treated with target temperature management (TTM). This prospective, multicenter observational study (The CRITICAL Study) carried out between July 1, 2012 and December 31, 2014 in Osaka Prefecture, Japan involving 13 critical care medical centers (CCMCs) and one non-CCMC with an emergency department. This study included patients ≥18 years of age who underwent an OHCA, for whom resuscitation was attempted by Emergency Medical Services personnel and were then transported to participating institutions, and who were then treated with TTM. Based on the serum albumin concentration upon hospital arrival, involved patients were divided into four quartiles (Q1-Q4) defined as Q1 (<3.0 g/dL), Q2 (≥3.0, <3.4 g/dL), Q3 (≥3.4, <3.8 g/dL), and Q4 (≥3.8 g/dL). The primary outcome of this study was 1-month survival with neurologically favorable outcome defined by cerebral performance category 1 or 2. During the study period, a total of 327 were eligible for our analysis. The overall proportion of neurologically favorable outcome was 33.0% (108/327). The Q4 group had the highest proportion of neurologically favorable outcome (52.5% [48/91]), followed by Q3 (34.5% [30/87]), Q2 (27.3% [21/77]), and Q1 (12.5% [9/72]). The multivariable logistic regression analysis demonstrated that the proportion of neurologically favorable outcome was significantly higher in the Q4 group than that in the Q1 group (adjusted odds ratio 10.39; 95% confidence interval 3.36-32.17). The adjusted proportion of neurologically favorable outcome increased in a stepwise fashion across increasing quartiles (p < 0.001). In this study, higher serum albumin concentration upon hospital arrival had a positive association with neurologically favorable outcome after OHCA in a dose-dependent manner.
Collapse
Affiliation(s)
- Tasuku Matsuyama
- 1 Department of Emergency Medicine, Kyoto Prefectural University of Medicine , Kyoto, Japan
| | - Taku Iwami
- 2 Kyoto University Health Services , Kyoto, Japan
| | - Tomoki Yamada
- 3 Department of Traumatology and Acute Critical Medicine, Osaka University Graduate School of Medicine , Suita, Japan .,4 Emergency and Critical Care Medical Center , Osaka Police Hospital, Osaka, Japan
| | - Koichi Hayakawa
- 5 Department of Emergency and Critical Care Medicine, Kansai Medical University , Takii Hospital, Moriguchi, Japan
| | - Kazuhisa Yoshiya
- 3 Department of Traumatology and Acute Critical Medicine, Osaka University Graduate School of Medicine , Suita, Japan
| | - Taro Irisawa
- 3 Department of Traumatology and Acute Critical Medicine, Osaka University Graduate School of Medicine , Suita, Japan
| | - Yoshio Abe
- 6 Department of Emergency Medicine, Tane General Hospital , Osaka, Japan
| | - Tetsuro Nishimura
- 7 Department of Traumatology and Critical Care Medicine, Osaka City University , Osaka, Japan
| | - Toshifumi Uejima
- 8 Department of Emergency and Critical Care Medicine, Kinki University School of Medicine , Osaka-Sayama, Japan
| | - Yasuo Ohishi
- 9 Osaka Mishima Emergency Critical Care Center , Takatsuki, Japan
| | - Takeyuki Kiguchi
- 2 Kyoto University Health Services , Kyoto, Japan .,10 Critical Care and Trauma Center, Osaka General Medical Center , Osaka, Japan
| | - Masashi Kishi
- 4 Emergency and Critical Care Medical Center , Osaka Police Hospital, Osaka, Japan
| | - Masafumi Kishimoto
- 11 Osaka Prefectural Nakakawachi Medical Center of Acute Medicine , Higashi-Osaka, Japan
| | - Shota Nakao
- 12 Senshu Trauma and Critical Care Center , Osaka, Japan
| | - Yasuyuki Hayashi
- 13 Senri Critical Care Medical Center , Saiseikai Senri Hospital, Suita, Japan
| | - Taku Sogabe
- 14 Traumatology and Critical Care Medical Center , National Hospital Organization Osaka National Hospital, Osaka, Japan
| | - Takaya Morooka
- 15 Emergency and Critical Care Medical Center , Osaka City General Hospital, Osaka, Japan
| | | | | | | | - Tomoko Fujii
- 2 Kyoto University Health Services , Kyoto, Japan
| | - Junya Sado
- 16 Division of Environmental Medicine and Population Sciences, Department of Social and Environmental Medicine, Graduate School of Medicine, Osaka University , Osaka, Japan
| | | | - Takeshi Shimazu
- 3 Department of Traumatology and Acute Critical Medicine, Osaka University Graduate School of Medicine , Suita, Japan
| | - Tetsuhisa Kitamura
- 16 Division of Environmental Medicine and Population Sciences, Department of Social and Environmental Medicine, Graduate School of Medicine, Osaka University , Osaka, Japan
| |
Collapse
|
24
|
Ku LC, Wu H, Greenberg RG, Hill KD, Gonzalez D, Hornik CP, Berezny A, Guptill JT, Jiang W, Zheng N, Cohen-Wolkowiez M, Melloni C. Use of Therapeutic Drug Monitoring, Electronic Health Record Data, and Pharmacokinetic Modeling to Determine the Therapeutic Index of Phenytoin and Lamotrigine. Ther Drug Monit 2016; 38:728-737. [PMID: 27764025 PMCID: PMC5113813 DOI: 10.1097/ftd.0000000000000354] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Defining a drug's therapeutic index (TI) is important for patient safety and regulating the development of generic drugs. For many drugs, the TI is unknown. A systematic approach was developed to characterize the TI of a drug using therapeutic drug monitoring and electronic health record (EHR) data with pharmacokinetic (PK) modeling. This approach was first tested on phenytoin, which has a known TI, and then applied to lamotrigine, which lacks a defined TI. METHODS Retrospective EHR data from patients in a tertiary hospital were used to develop phenytoin and lamotrigine population PK models and to identify adverse events (anemia, thrombocytopenia, and leukopenia) and efficacy outcomes (seizure-free). Phenytoin and lamotrigine concentrations were simulated for each day with an adverse event or seizure. Relationships between simulated concentrations and adverse events and efficacy outcomes were used to calculate the TI for phenytoin and lamotrigine. RESULTS For phenytoin, 93 patients with 270 total and 174 free concentrations were identified. A de novo 1-compartment PK model with Michaelis-Menten kinetics described the data well. Simulated average total and free concentrations of 10-15 and 1.0-1.5 mcg/mL were associated with both adverse events and efficacy in 50% of patients, resulting in a TI of 0.7-1.5. For lamotrigine, 45 patients with 53 concentrations were identified. A published 1-compartment model was adapted to characterize the PK data. No relationships between simulated lamotrigine concentrations and safety or efficacy endpoints were seen; therefore, the TI could not be calculated. CONCLUSIONS This approach correctly determined the TI of phenytoin but was unable to determine the TI of lamotrigine due to a limited sample size. The use of therapeutic drug monitoring and EHR data to aid in narrow TI drug classification is promising, but it requires an adequate sample size and accurate characterization of concentration-response relationships.
Collapse
Affiliation(s)
- Lawrence C. Ku
- Duke Clinical Research Institute, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Pediatrics, Duke University School of Medicine, Durham, North Carolina, USA
| | - Huali Wu
- Duke Clinical Research Institute, Duke University School of Medicine, Durham, North Carolina, USA
| | - Rachel G. Greenberg
- Duke Clinical Research Institute, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Pediatrics, Duke University School of Medicine, Durham, North Carolina, USA
| | - Kevin D. Hill
- Duke Clinical Research Institute, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Pediatrics, Duke University School of Medicine, Durham, North Carolina, USA
| | - Daniel Gonzalez
- Division of Pharmacotherapy and Experimental Therapeutics, UNC Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Christoph P. Hornik
- Duke Clinical Research Institute, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Pediatrics, Duke University School of Medicine, Durham, North Carolina, USA
| | - Alysha Berezny
- Duke Clinical Research Institute, Duke University School of Medicine, Durham, North Carolina, USA
| | - Jeffrey T. Guptill
- Duke Clinical Research Institute, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Neurology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Wenlei Jiang
- Office of Generic Drugs, US Food and Drug Administration, Silver Spring, MD, USA
| | - Nan Zheng
- Office of Generic Drugs, US Food and Drug Administration, Silver Spring, MD, USA
| | - Michael Cohen-Wolkowiez
- Duke Clinical Research Institute, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Pediatrics, Duke University School of Medicine, Durham, North Carolina, USA
| | - Chiara Melloni
- Duke Clinical Research Institute, Duke University School of Medicine, Durham, North Carolina, USA
| |
Collapse
|
25
|
Clark SL, Leloux MR, Dierkhising RA, Cascino GD, Hocker SE. IV fosphenytoin in obese patients: Dosing strategies, safety, and efficacy. Neurol Clin Pract 2016; 7:45-52. [PMID: 29849211 DOI: 10.1212/cpj.0000000000000322] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Background Previous studies evaluated the disposition of IV phenytoin loading doses and found that obese patients had increased drug distribution into excess body weight, larger volumes of distribution, and longer half-lives when compared to their nonobese counterparts. We assess the safety and efficacy of fosphenytoin loading doses in patients with different body mass indices (BMIs). Methods A retrospective chart review was conducted in 410 patients who received fosphenytoin. Patients were divided into 2 groups: BMI <30 (nonobese) and BMI ≥30 (obese). Patient demographics, fosphenytoin dose administered in mg/kg body weight, renal and liver function tests, fosphenytoin drug levels, and pre- and post-fosphenytoin administration vital signs were collected to assess for adverse events. Necessity of additional antiepileptic loading doses was used as a surrogate for clinical efficacy. Results The median dose of fosphenytoin administered was 19 mg/kg (interquartile range 15-20). The most frequently encountered adverse event was hypotension, which occurred in 39% of the cohort. Using a Bonferroni adjustment for multiple comparisons, there were no differences in adverse events between the 2 groups. The need for additional antiepileptic loading doses was not different between the 2 groups (p = 0.07). Conclusions The incidence of adverse events and the need for repeat loading antiepileptic medications was similar between the 2 groups. From our findings, the patients in our study did not receive empiric loading dose adjustments and the current method of loading fosphenytoin achieves similar outcomes, regardless of the patient's BMI.
Collapse
|
26
|
Abstract
Toxic epidermal necrolysis (TEN) is a serious, life-threatening skin reaction characterized by severe exfoliation and destruction of the epidermis of the skin. In most TEN cases, drugs are believed to be the causative agent; antipsychotics, antiepileptics, and other medications such as sulfonamides are among the most common causes of drug-induced TEN. Phenytoin, a commonly prescribed medication for seizure, was found to cause TEN. Evidence-based treatment guidelines are lacking, so the best strategy is to identify and avoid potential risk factors and to provide intensive supportive care. The aim of this literature review is to focus on phenytoin-induced TEN, to explore the risk factors, and to highlight the possible treatment options once phenytoin-induced TEN is confirmed.
Collapse
Affiliation(s)
- Osama M Al-Quteimat
- Department of Pharmacy Services, Clevevland Clinic Abu Dhabi, Abu Dhabi, United Arab Emirates
| |
Collapse
|
27
|
Milka Darlic Q, Amudio C. FARMACOLOGÍA EN EL PACIENTE NEUROCRÍTICO, FOCO EN LA TERAPIA ANTICONVULSIVANTE. REVISTA MÉDICA CLÍNICA LAS CONDES 2016. [DOI: 10.1016/j.rmclc.2016.09.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
|
28
|
Cheng W, Kiang TKL, Bring P, Ensom MHH. Predictive Performance of the Winter-Tozer and Derivative Equations for Estimating Free Phenytoin Concentration. Can J Hosp Pharm 2016; 69:269-79. [PMID: 27621486 DOI: 10.4212/cjhp.v69i4.1573] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
BACKGROUND The Winter-Tozer equation for estimating free phenytoin concentration is biased and imprecise. Alternative predictive equations are available, but most remain unvalidated. OBJECTIVES To assess the bias and precision of the Winter-Tozer equation and selected derivative equations in predicting free phenytoin concentration and to derive new equations with better predictive performance. METHODS A retrospective chart review (for patients with samples drawn for free phenytoin concentration between September 2008 and September 2013) was conducted for 3 subpopulations (critical care, general medicine, neurology) in one hospital. Patients were included if older than 18 years with values for free phenytoin concentration available and were excluded if phenytoin was not at steady state or if they were undergoing hemodialysis or receiving enzyme inhibitors or inducers that would affect phenytoin clearance. The predictive performance measures used were mean prediction error (MPE), root mean square error, and Bland-Altman plots. Spearman rank correlation and multiple linear regression were performed with log-transformed data. RESULTS In total, 133 patients were included (70 men [53%]; mean age ± standard deviation 64 ± 19 years; serum creatinine 90.4 ± 64.0 µmol/L; albumin 26.4 ± 7.0 g/L). In the combined population, the Winter-Tozer equation (MPE 1.7 µmol/L, 95% confidence interval [CI] 1.5 to 1.9) and the Anderson equation (MPE 0.5 µmol/L, 95% CI 0.3 to 0.7) over-predicted free phenytoin concentration, whereas the first Kane equation tended to underpredict free phenytoin (MPE -0.2 µmol/L, 95% CI -0.4 to 0.0), and the second Kane equation significantly underpredicted free phenytoin (MPE -0.3 µmol/L, 95% CI -0.5 to -0.1). In each subpopulation, the Winter-Tozer equation overpredicted true concentration with greater bias and imprecision. All equations performed poorly in the critical care subpopulation. Only albumin (R (2) = 0.09) and total phenytoin concentration (R (2) = 0.53) were correlated with free phenytoin concentration. The equation derived by multiple linear regression exhibited significantly less bias and imprecision than the Winter-Tozer equation in the validation set (p < 0.05). A new, user-friendly equation, specific to the authors' patient population, was derived, which had an albumin coefficient of 0.275. CONCLUSIONS Relatively poor predictive performance of the Winter-Tozer and derivative equations calls for more precise and less biased equations. The novel equations presented here, which had better predictive performance for free phenytoin concentration and were based on a large sample of adult patients, should be further validated in other institutions.
Collapse
Affiliation(s)
- Wendy Cheng
- , BSc(Pharm), ACPR, is a Clinical Pharmacist, Department of Pharmacy, Vancouver General Hospital, Vancouver, British Columbia
| | - Tony K L Kiang
- , BSc(Pharm), PhD, ACPR, is a Clinical Pharmacy Specialist, Department of Pharmacy, Vancouver General Hospital, Vancouver, British Columbia
| | - Penny Bring
- , BSc(Pharm), ACPR, PharmD, is a Clinical Pharmacy Specialist, Department of Pharmacy, Surrey Memorial Hospital, Surrey, British Columbia
| | - Mary H H Ensom
- , BS(Pharm), PharmD, FASHP, FCCP, FCSHP, FCAHS, is Professor, Faculty of Pharmaceutical Sciences and Distinguished University Scholar, The University of British Columbia, and Clinical Pharmacy Specialist, Department of Pharmacy, Children's and Women's Health Centre of British Columbia, Vancouver, British Columbia
| |
Collapse
|
29
|
Smetana KS, Cook AM, Bastin MLT, Oyler DR. Antiepileptic dosing for critically ill adult patients receiving renal replacement therapy. J Crit Care 2016; 36:116-124. [PMID: 27546759 DOI: 10.1016/j.jcrc.2016.06.023] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 06/06/2016] [Accepted: 06/28/2016] [Indexed: 11/28/2022]
Abstract
OBJECTIVES The aim of this review was to evaluate current literature for dosing recommendations for the use of antiepileptic medications in patients receiving renal replacement therapy (RRT). DATA SOURCES With the assistance of an experienced medical librarian specialized in pharmacy and toxicology, we searched MEDLINE, EMBASE, CINAHL, Web of Science, WorldCat, and Scopus through May 2016. STUDY SELECTION AND DATA EXTRACTION Four hundred three articles were screened for inclusion, of which 130 were identified as potentially relevant. Micromedex® DRUGDEX as well as package inserts were used to obtain known pharmacokinetic properties and dosage adjustment recommendations in RRT if known. DATA SYNTHESIS Data regarding antiepileptic drug use in RRT are limited and mostly consist of case reports limiting our proposed dosing recommendations. Known pharmacokinetic parameters should guide dosing, and recommendations are provided where possible. CONCLUSION Additional studies are necessary before specific dosing recommendations can be made for most antiepileptic drugs in critically ill patients receiving RRT, specifically with newer agents.
Collapse
Affiliation(s)
- Keaton S Smetana
- University of Kentucky HealthCare, Department of Pharmacy, Lexington, KY.
| | - Aaron M Cook
- University of Kentucky HealthCare, Department of Pharmacy, Lexington, KY; University of Kentucky College of Pharmacy, Department of Pharmacy Practice and Science (UK College of Pharmacy), University of Kentucky, Lexington, KY.
| | - Melissa L Thompson Bastin
- University of Kentucky HealthCare, Department of Pharmacy, Lexington, KY; University of Kentucky College of Pharmacy, Department of Pharmacy Practice and Science (UK College of Pharmacy), University of Kentucky, Lexington, KY.
| | - Douglas R Oyler
- University of Kentucky HealthCare, Department of Pharmacy, Lexington, KY; University of Kentucky College of Pharmacy, Department of Pharmacy Practice and Science (UK College of Pharmacy), University of Kentucky, Lexington, KY.
| |
Collapse
|
30
|
Abstract
Antiepileptic drugs (AEDs) are routinely prescribed for the management of a variety of neurologic and psychiatric conditions, including epilepsy and epilepsy syndromes. Physiologic changes due to aging, pregnancy, nutritional status, drug interactions, and diseases (ie, those involving liver and kidney function) can affect pharmacokinetics of AEDs. This review discusses foundational pharmacokinetic characteristics of AEDs currently available in the United States, including clobazam but excluding the other benzodiazepines. Commonalities of pharmacokinetic properties of AEDs are discussed in detail. Important differences among AEDs and clinically relevant pharmacokinetic interactions in absorption, distribution, metabolism, and/or elimination associated with AEDs are highlighted. In general, newer AEDs have more predictable kinetics and lower risks for drug interactions. This is because many are minimally or not bound to serum proteins, are primarily renally cleared or metabolized by non–cytochrome P450 isoenzymes, and/or have lower potential to induce/inhibit various hepatic enzyme systems. A clear understanding of the pharmacokinetic properties of individual AEDs is essential in creating a safe and effective treatment plan for a patient.
Collapse
Affiliation(s)
- Marketa Marvanova
- Chair and Associate Professor, College of Health Professions, School of Pharmacy, North Dakota State University, Fargo, North Dakota,
| |
Collapse
|
31
|
Kiang TKL, Ensom MHH. A Comprehensive Review on the Predictive Performance of the Sheiner-Tozer and Derivative Equations for the Correction of Phenytoin Concentrations. Ann Pharmacother 2016; 50:311-25. [PMID: 26825643 DOI: 10.1177/1060028016628166] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
OBJECTIVE In settings where free phenytoin concentrations are not available, the Sheiner-Tozer equation-Corrected total phenytoin concentration = Observed total phenytoin concentration/[(0.2 × Albumin) + 0.1]; phenytoin in µg/mL, albumin in g/dL-and its derivative equations are commonly used to correct for altered phenytoin binding to albumin. The objective of this article was to provide a comprehensive and updated review on the predictive performance of these equations in various patient populations. DATA SOURCES A literature search of PubMed, EMBASE, and Google Scholar was conducted using combinations of the following terms: Sheiner-Tozer, Winter-Tozer, phenytoin, predictive equation, precision, bias, free fraction. STUDY SELECTION AND DATA EXTRACTION All English-language articles up to November 2015 (excluding abstracts) were evaluated. DATA SYNTHESIS This review shows the Sheiner-Tozer equation to be biased and imprecise in various critical care, head trauma, and general neurology patient populations. Factors contributing to bias and imprecision include the following: albumin concentration, free phenytoin assay temperature, experimental conditions (eg, timing of concentration sampling, steady-state dosing conditions), renal function, age, concomitant medications, and patient type. Although derivative equations using varying albumin coefficients have improved accuracy (without much improvement in precision) in intensive care and elderly patients, these equations still require further validation. CONCLUSIONS Further experiments are also needed to yield derivative equations with good predictive performance in all populations as well as to validate the equations' impact on actual patient efficacy and toxicity outcomes. More complex, multivariate predictive equations may be required to capture all variables that can potentially affect phenytoin pharmacokinetics and clinical therapeutic outcomes.
Collapse
Affiliation(s)
- Tony K L Kiang
- The University of British Columbia, Vancouver, BC, Canada Vancouver General Hospital, Vancouver, BC, Canada
| | - Mary H H Ensom
- The University of British Columbia, Vancouver, BC, Canada Children's and Women's Health Centre of British Columbia, Vancouver, BC, Canada
| |
Collapse
|
32
|
Buckley MS, Reeves BA, Barletta JF, Bikin DS. Correlation of Free and Total Phenytoin Serum Concentrations in Critically Ill Patients. Ann Pharmacother 2016; 50:276-81. [PMID: 26783351 DOI: 10.1177/1060028015627468] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Phenytoin is a common medication for seizure treatment and prophylaxis in the intensive care unit (ICU). The clinical utility of the Sheiner-Tozer equation for adjusting total phenytoin levels for hypoalbuminemia remains controversial. OBJECTIVE The purpose of this study was to evaluate the correlation of this formula in predicting phenytoin serum concentrations. METHODS A retrospective cohort study was conducted in the adult ICU between January 1, 2010, and June 21, 2013. Patients meeting the following study criteria were included: age ≥18 years, admission to the ICU, simultaneously drawn total and free serum phenytoin concentrations with albumin ≤48 hours of phenytoin draws. Study end points were the correlation as well as the level of agreement in the interpretation of the free and adjusted phenytoin concentrations using the Sheiner-Tozer formula in critically ill patients with hypoalbuminemia. RESULTS A total of 238 patients were analyzed. Mean adjusted total phenytoin and free levels were 16.1 ± 8.1 and 1.5 ± 0.8 µg/mL, respectively (r = 0.817; P < 0.001). Absolute agreement with level interpretation between adjusted total phenytoin and free levels was 77% (κ = 0.633; P < 0.001). Adjusted phenytoin serum concentrations more frequently overestimated the free level. CONCLUSIONS There is a significant correlation between free and adjusted total phenytoin levels using the Sheiner-Tozer equation in critically ill patients. However, disagreement was noted with interpretation, primarily because of the adjusted concentration overestimating the free level. This imprecision may lead to inaccurate decision making regarding the management of phenytoin in this patient population. Thus, free phenytoin levels should be utilized.
Collapse
Affiliation(s)
| | | | | | - Dale S Bikin
- Banner-University Medical Center Phoenix, AZ, USA
| |
Collapse
|
33
|
Tobler A, Hösli R, Mühlebach S, Huber A. Free phenytoin assessment in patients: measured versus calculated blood serum levels. Int J Clin Pharm 2016; 38:303-9. [PMID: 26746902 DOI: 10.1007/s11096-015-0241-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2015] [Accepted: 12/20/2015] [Indexed: 10/22/2022]
Abstract
BACKGROUND Total serum drug levels are routinely determined for the therapeutic drug monitoring of selected, difficult-to-dose drugs. For some of these drugs, however, knowledge of the free fraction is necessary to adapt correct dosing. Phenytoin, with its non-linear pharmacokinetics, >90 % albumin binding and slow elimination rate, is such a drug requiring individualization in patients, especially if rapid intravenous loading and subsequent dose adaptation is needed. In a prior long-term investigation, we showed the excellent performance of pharmacy-assisted Bayesian forecasting support for optimal dosing in hospitalized patients treated with phenytoin. In a subgroup analysis, we evaluated the suitability of the Sheiner-Tozer algorithm to calculate the free phenytoin fraction in hypoalbuminemic patients. OBJECTIVE To test the usefulness of the Sheiner-Tozer algorithm for the correct estimation of the free phenytoin concentrations in hospitalized patients. SETTING A Swiss tertiary care hospital. METHOD Free phenytoin plasma concentration was calculated from total phenytoin concentration in hypoalbuminemic patients and compared with the measured free phenytoin. The patients were separated into a low (35 ≤ albumin ≥ 25 g/L) and a very low group (albumin <25 g/L) for comparing and statistically analyzing the calculated and the measured free phenytoin concentration. MAIN OUTCOME MEASURES Calculated and the measured free phenytoin concentration. RESULTS The calculated (1.2 mg/L (SD = 0.7) and the measured (1.1 mg/L (SD = 0.5) free phenytoin concentration correlated. The mean difference in the low and the very low albumin group was: 0.10 mg/L (SD = 1.4) (n = 11) and 0.13 mg/L (SD = 0.24) (n = 12), respectively. Although the variability of the data could be a bias, no statistically significant difference between the groups was found: t test (p = 0.78), the Passing-Bablok regression, the Spearman's rank correlation coefficient of r = 0.907 and p = 0.00. The Bland-Altman plot including the regression analysis revealed no systematic differences between the calculated and the measured value [M = 0.11 (SD = 0.28)]. CONCLUSION In absence of a free phenytoin plasma concentration measurement also in hypoalbuminemic patients, the Sheiner-Tozer algorithm represents a useful tool to assist therapeutic monitoring to calculate or control free phenytoin by using total phenytoin and the albumin concentration.
Collapse
Affiliation(s)
- Andrea Tobler
- Division of Clinical Pharmacy and Epidemiology and Hospital Pharmacy, University of Basel, Spitalstrasse 26, 4031, Basel, Switzerland
| | - Raphael Hösli
- Division of Clinical Pharmacy and Epidemiology and Hospital Pharmacy, University of Basel, Spitalstrasse 26, 4031, Basel, Switzerland
| | - Stefan Mühlebach
- Division of Clinical Pharmacy and Epidemiology and Hospital Pharmacy, University of Basel, Spitalstrasse 26, 4031, Basel, Switzerland.
| | - Andreas Huber
- Kantonsspital Aarau, Tellstrasse 25, 5001, Aarau, Switzerland
| |
Collapse
|
34
|
Impact of Body Habitus on Phenytoin Levels Following Fosphenytoin Loading Dose in Pediatric Patients. Ther Drug Monit 2015; 37:772-5. [DOI: 10.1097/ftd.0000000000000241] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
35
|
Habib MMW, Abdelfattah MAO, Abadi AH. Design and Synthesis of Novel Phenylpiperazine Derivatives as Potential Anticonvulsant Agents. Arch Pharm (Weinheim) 2015; 348:868-74. [DOI: 10.1002/ardp.201500272] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 09/22/2015] [Accepted: 09/28/2015] [Indexed: 11/10/2022]
Affiliation(s)
- Monica M. W. Habib
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy and Biotechnology; German University in Cairo; Cairo Egypt
| | - Mohamed A. O. Abdelfattah
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy and Biotechnology; German University in Cairo; Cairo Egypt
- American University of The Middle East; Egaila Kuwait
| | - Ashraf H. Abadi
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy and Biotechnology; German University in Cairo; Cairo Egypt
| |
Collapse
|
36
|
Allison E, Evans RG, Wall S, Johnson D, Das S. Postoperative hypoalbuminemia following surgery related to craniosynostosis. Paediatr Anaesth 2015; 25:924-8. [PMID: 26033411 DOI: 10.1111/pan.12689] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/12/2015] [Indexed: 11/27/2022]
Abstract
BACKGROUND An episode of postoperative phenytoin toxicity in a patient undergoing surgery related to craniosynostosis highlighted the presence of hypoalbuminemia. We believe that hypoalbuminemia contributed to the altered pharmacokinetics of phenytoin in this case. OBJECTIVES To establish the incidence of postoperative hypoalbuminemia in patients undergoing surgery related to craniosynostosis and to investigate the likely etiology. METHODS Data on 114 patients undergoing surgery for craniosynostosis over a 2-year period at Oxford Children's Hospital, between May 2011 and May 2013, were retrospectively reviewed. Twenty-two patients were excluded due to incomplete data. This cohort represents the entire population for whom transfusion data had been formally collected at our institution. Preoperative and day 1 postoperative serum albumin levels were collected from the hospital laboratory database. Data regarding blood loss and intra-operative fluid management were reviewed from the anesthetic database. Linear regression analysis was used to establish the relationship between percentage drop in serum albumin with: (i) milliliters per kilogram (ml·kg(-1)) volume of albumin-poor fluids used intra-operatively and (ii) percentage estimated red cell mass loss. RESULTS All patients experienced a statistically significant drop in serum albumin. The mean difference in albumin was 17.1 g·l(-1), 95% CI (16.1-18.0) (P < 0.001). Expressed as a percentage, the mean reduction was 37.9% (range 16-61%), SD 9.7. The decrease in albumin was associated with an increase in estimated red cell mass loss (P < 0.001) and an increased ml·kg(-1) volume of albumin-poor fluids given (P < 0.001). CONCLUSION Hemodilution due to large volume blood loss and transfusion with albumin-poor fluids is strongly associated with postoperative hypoalbuminemia in patients undergoing surgery related to craniosynostosis. Practitioners should be aware of this risk and the implications of postoperative hypoalbuminemia in this population.
Collapse
Affiliation(s)
- Elizabeth Allison
- Nuffield Department of Anaesthesia, Oxford University Hospitals NHS Trust, Oxford, UK
| | - Russell G Evans
- Nuffield Department of Anaesthesia, Oxford University Hospitals NHS Trust, Oxford, UK
| | - Steven Wall
- Oxford Craniofacial Unit, Department of Plastic Surgery, Oxford University Hospitals NHS Trust, Oxford, UK
| | - David Johnson
- Oxford Craniofacial Unit, Department of Plastic Surgery, Oxford University Hospitals NHS Trust, Oxford, UK
| | - Sumit Das
- Nuffield Department of Anaesthesia, Oxford University Hospitals NHS Trust, Oxford, UK
| |
Collapse
|
37
|
Brancaccio A, Giuliano C, McNorton K, Delgado G. Impact of a phenytoin loading dose program in the emergency department. Am J Health Syst Pharm 2015; 71:1862-9. [PMID: 25320136 DOI: 10.2146/ajhp140039] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
PURPOSE The use of a combined physician-and pharmacist-directed phenytoin loading dose program in an emergency department (ED) was evaluated. METHODS This single-center, observational, preimplementation-postimplementation study evaluated adult patients who received a phenytoin loading dose in the ED. The primary outcome compared the proportion of optimal phenytoin loading doses in the preimplementation and postimplementation groups. The postimplementation group was further stratified into pharmacist- and prescriber-dosing groups. Other outcomes evaluated included the numbers of appropriate serum phenytoin concentrations measured, adverse drug reactions (ADRs), and recurrence of seizures within 24 hours of loading dose administration in the preimplementation and postimplementation groups. RESULTS There was no difference in the proportion of optimal phenytoin loading doses between the preimplementation and postimplementation groups (50% versus 62%, respectively; p=0.19). When stratified by individual groups, the rate of optimal phenytoin loading doses increased by 64% in the postimplementation pharmacist group (50% versus 82%, p=0.007), while the rate in the prescriber-dosing group remained relatively unchanged (50% versus 49%, p=0.91). The number of appropriate serum phenytoin concentrations significantly improved in the postimplementation versus preimplementation group (65% versus 40%, p=0.025). Rates of ADRs and recurrence of seizures did not differ across the study groups. CONCLUSION No change in the percentage of optimal phenytoin loading doses in the ED was observed after implementation of a combined pharmacist- and physician- dosing program. When stratified into pharmacist or prescriber dosing, the pharmacist-led dosing program significantly improved the proportion of patients who received optimal phenytoin loading doses.
Collapse
Affiliation(s)
- Adam Brancaccio
- Adam Brancaccio, Pharm..D., BCPS, is Clinical Pharmacist Generalist-Internal Medicine, University of Michigan Health System, Ann Arbor, and Adjunct Clinical Faculty, University of Michigan College of Pharmacy, Ann Arbor; at the time of writing, he was Postgraduate Year 1 Pharmacy Practice Resident, Department of Pharmacy, St. John Hospital and Medical Center (SJHMC), Detroit, MI. Christopher Giuliano, Pharm.D., is Assistant Professor, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, and Clinical Specialist, Internal Medicine, Department of Pharmacy, SJHMC. Kelly McNorton, Pharm.D., BCPS, is Clinical Pharmacy Specialist, Critical Care; and George Delgado Jr., Pharm.D., is Clinical Pharmacy Specialist, Emergency Medicine/Infectious Diseases, Department of Pharmacy, SJHMC
| | - Christopher Giuliano
- Adam Brancaccio, Pharm..D., BCPS, is Clinical Pharmacist Generalist-Internal Medicine, University of Michigan Health System, Ann Arbor, and Adjunct Clinical Faculty, University of Michigan College of Pharmacy, Ann Arbor; at the time of writing, he was Postgraduate Year 1 Pharmacy Practice Resident, Department of Pharmacy, St. John Hospital and Medical Center (SJHMC), Detroit, MI. Christopher Giuliano, Pharm.D., is Assistant Professor, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, and Clinical Specialist, Internal Medicine, Department of Pharmacy, SJHMC. Kelly McNorton, Pharm.D., BCPS, is Clinical Pharmacy Specialist, Critical Care; and George Delgado Jr., Pharm.D., is Clinical Pharmacy Specialist, Emergency Medicine/Infectious Diseases, Department of Pharmacy, SJHMC.
| | - Kelly McNorton
- Adam Brancaccio, Pharm..D., BCPS, is Clinical Pharmacist Generalist-Internal Medicine, University of Michigan Health System, Ann Arbor, and Adjunct Clinical Faculty, University of Michigan College of Pharmacy, Ann Arbor; at the time of writing, he was Postgraduate Year 1 Pharmacy Practice Resident, Department of Pharmacy, St. John Hospital and Medical Center (SJHMC), Detroit, MI. Christopher Giuliano, Pharm.D., is Assistant Professor, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, and Clinical Specialist, Internal Medicine, Department of Pharmacy, SJHMC. Kelly McNorton, Pharm.D., BCPS, is Clinical Pharmacy Specialist, Critical Care; and George Delgado Jr., Pharm.D., is Clinical Pharmacy Specialist, Emergency Medicine/Infectious Diseases, Department of Pharmacy, SJHMC
| | - George Delgado
- Adam Brancaccio, Pharm..D., BCPS, is Clinical Pharmacist Generalist-Internal Medicine, University of Michigan Health System, Ann Arbor, and Adjunct Clinical Faculty, University of Michigan College of Pharmacy, Ann Arbor; at the time of writing, he was Postgraduate Year 1 Pharmacy Practice Resident, Department of Pharmacy, St. John Hospital and Medical Center (SJHMC), Detroit, MI. Christopher Giuliano, Pharm.D., is Assistant Professor, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, and Clinical Specialist, Internal Medicine, Department of Pharmacy, SJHMC. Kelly McNorton, Pharm.D., BCPS, is Clinical Pharmacy Specialist, Critical Care; and George Delgado Jr., Pharm.D., is Clinical Pharmacy Specialist, Emergency Medicine/Infectious Diseases, Department of Pharmacy, SJHMC
| |
Collapse
|
38
|
Inappropriate utilization of the Sheiner-Tozer equation to determine phenytoin toxicity. Am J Emerg Med 2015; 33:467-8. [DOI: 10.1016/j.ajem.2014.12.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 12/10/2014] [Indexed: 11/23/2022] Open
|
39
|
Vanstraelen K, Wauters J, Vercammen I, de Loor H, Maertens J, Lagrou K, Annaert P, Spriet I. Impact of hypoalbuminemia on voriconazole pharmacokinetics in critically ill adult patients. Antimicrob Agents Chemother 2014; 58:6782-9. [PMID: 25182655 PMCID: PMC4249353 DOI: 10.1128/aac.03641-14] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 08/23/2014] [Indexed: 01/30/2023] Open
Abstract
Setting the adequate dose for voriconazole is challenging due to its variable pharmacokinetics. We investigated the impact of hypoalbuminemia (<35 g/liter) on voriconazole pharmacokinetics in adult intensive care unit (ICU) patients treated with voriconazole (20 samples in 13 patients) as well as in plasma samples from ICU patients that had been spiked with voriconazole at concentrations of 1.5 mg/liter, 2.9 mg/liter, and 9.0 mg/liter (66 samples from 22 patients). Plasma albumin concentrations ranged from 13.8 to 38.7 g/liter. Total voriconazole concentrations in adult ICU patients treated with voriconazole ranged from 0.5 to 8.7 mg/liter. Unbound and bound voriconazole concentrations were separated using high-throughput equilibrium dialysis followed by liquid chromatography-tandem mass spectrometry (LC-MSMS). Multivariate analysis revealed a positive relationship between voriconazole plasma protein binding and plasma albumin concentrations (P < 0.001), indicating higher unbound voriconazole concentrations with decreasing albumin concentrations. The correlation is more pronounced in the presence of elevated bilirubin concentrations (P = 0.05). We therefore propose to adjust the measured total voriconazole concentrations in patients with abnormal plasma albumin and total serum bilirubin plasma concentrations who show adverse events potentially related to voriconazole via a formula that we developed. Assuming 50% protein binding on average and an upper limit of 5.5 mg/liter for total voriconazole concentrations, the upper limit for unbound voriconazole concentrations is 2.75 mg/liter. Alterations in voriconazole unbound concentrations caused by hypoalbuminemia and/or elevated bilirubin plasma concentrations cannot be countered immediately, due to the adult saturated hepatic metabolism. Consequently, increased unbound voriconazole concentrations can possibly cause adverse events, even when total voriconazole concentrations are within the reference range.
Collapse
Affiliation(s)
- Kim Vanstraelen
- Clinical Pharmacology and Pharmacotherapy, Department of Pharmaceutical and Pharmacological Sciences, University Hospitals Leuven, Leuven, Belgium
| | - Joost Wauters
- Clinical Department of General Internal Medicine, Medical Intensive Care Unit, University Hospitals Leuven, Leuven, Belgium
| | - Ine Vercammen
- Clinical Pharmacology and Pharmacotherapy, Department of Pharmaceutical and Pharmacological Sciences, University Hospitals Leuven, Leuven, Belgium
| | - Henriette de Loor
- Department of Microbiology and Immunology, Laboratory of Nephrology and Renal Transplantation, University Hospitals Leuven/KU Leuven, Leuven, Belgium
| | - Johan Maertens
- Clinical Department of Haematology, Acute Leukaemia and Stem Cell Transplantation Unit, University Hospitals Leuven, Leuven, Belgium
| | - Katrien Lagrou
- Clinical Department of Laboratory Medicine, Department of Microbiology and Immunology, University Hospitals Leuven, Leuven, Belgium
| | - Pieter Annaert
- Department of Pharmaceutical and Pharmacological Sciences, Drug Delivery and Disposition, KU Leuven, Leuven, Belgium
| | - Isabel Spriet
- Clinical Pharmacology and Pharmacotherapy, Department of Pharmaceutical and Pharmacological Sciences, University Hospitals Leuven, Leuven, Belgium
| |
Collapse
|
40
|
Reinhart WH, Lubszky S, Thöny S, Schulzki T. Interaction of injectable neurotropic drugs with the red cell membrane. Toxicol In Vitro 2014; 28:1274-9. [DOI: 10.1016/j.tiv.2014.06.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Revised: 06/12/2014] [Accepted: 06/23/2014] [Indexed: 11/30/2022]
|
41
|
Sirich TL, Plummer NS, Gardner CD, Hostetter TH, Meyer TW. Effect of increasing dietary fiber on plasma levels of colon-derived solutes in hemodialysis patients. Clin J Am Soc Nephrol 2014; 9:1603-10. [PMID: 25147155 DOI: 10.2215/cjn.00490114] [Citation(s) in RCA: 202] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
BACKGROUND AND OBJECTIVES Numerous uremic solutes are derived from the action of colon microbes. Two such solutes, indoxyl sulfate and p-cresol sulfate, have been associated with adverse outcomes in renal failure. This study tested whether increasing dietary fiber in the form of resistant starch would lower the plasma levels of these solutes in patients on hemodialysis. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Fifty-six patients on maintenance hemodialysis were randomly assigned to receive supplements containing resistant starch (n=28) or control starch (n=28) daily for 6 weeks in a study conducted between October 2010 and May 2013. Of these, 40 patients (20 in each group) completed the study and were included in the final analysis. Plasma indoxyl sulfate and p-cresol sulfate levels were measured at baseline and week 6. RESULTS Increasing dietary fiber for 6 weeks significantly reduced the unbound, free plasma level of indoxyl sulfate (median -29% [25th percentile, 75th percentile, -56, -12] for fiber versus -0.4% [-20, 34] for control, P=0.02). The reduction in free plasma levels of indoxyl sulfate was accompanied by a reduction in free plasma levels of p-cresol sulfate (r=0.81, P<0.001). However, the reduction of p-cresol sulfate levels was of lesser magnitude and did not achieve significance (median -28% [-46, 5] for fiber versus 4% [-28, 36] for control, P=0.05). CONCLUSIONS Increasing dietary fiber in hemodialysis patients may reduce the plasma levels of the colon-derived solutes indoxyl sulfate and possibly p-cresol sulfate without the need to intensify dialysis treatments. Further studies are required to determine whether such reduction provides clinical benefits.
Collapse
Affiliation(s)
- Tammy L Sirich
- Departments of Medicine, Veterans Affairs Palo Alto Health Care System and Stanford University, Palo Alto, California; and
| | - Natalie S Plummer
- Departments of Medicine, Veterans Affairs Palo Alto Health Care System and Stanford University, Palo Alto, California; and
| | - Christopher D Gardner
- Departments of Medicine, Veterans Affairs Palo Alto Health Care System and Stanford University, Palo Alto, California; and
| | - Thomas H Hostetter
- Department of Medicine, Case Western Reserve University, Cleveland, Ohio
| | - Timothy W Meyer
- Departments of Medicine, Veterans Affairs Palo Alto Health Care System and Stanford University, Palo Alto, California; and
| |
Collapse
|
42
|
Oltrogge KM, Peppard WJ, Saleh M, Regner KR, Herrmann DJ. Phenytoin removal by continuous venovenous hemofiltration. Ann Pharmacother 2014; 47:1218-22. [PMID: 24259740 DOI: 10.1177/1060028013503131] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE To describe 2 cases of clinically significant phenytoin removal during continuous venovenous hemofiltration (CVVH) and review the relevant literature regarding phenytoin removal by renal replacement modalities. CASE SUMMARY A 64-year-old female with chronic kidney disease and cirrhosis was admitted to the intensive care unit (ICU) with a traumatic subdural hematoma and seizures. The patient received a loading dose of intravenous phenytoin 1000 mg, followed by maintenance intravenous administration of phenytoin 100 mg and levetiracetam 250 mg every 12 hours. CVVH was initiated for acidosis. A 63-year-old male was admitted to the ICU after cardiac surgery complicated by hypotension. CVVH was initiated for fluid overload, and phenytoin was initiated 3 days later for seizures. A loading dose of intravenous phenytoin 2700 mg was administered, followed by maintenance dosing of intravenous phenytoin 150 mg every 8 hours. Concentrations of unbound phenytoin in serum and CVVH effluent samples were measured during concomitant treatment in each patient. In both patients, serum and effluent concentrations of unbound phenytoin fell steadily while they were on CVVH. Clearance of phenytoin by CVVH was calculated, as was the daily removal of phenytoin, as a percentage of total daily phenytoin dosage during each sampling period. Phenytoin clearance by CVVH ranged from 11 to 13 mL/min in these patients. DISCUSSION The clearance of phenytoin with CVVH in these 2 patients was much higher than the renal clearance of phenytoin reported in healthy volunteers with normal renal function. Previous case reports have demonstrated that only small, clinically insignificant amounts of phenytoin are removed by hemodialysis, and the only published report of phenytoin removal by continuous renal replacement therapy used hemofiltration rates much lower than those used in the 2 cases described here. CONCLUSIONS These cases demonstrate that a substantial amount-approximately 30%-of total daily phenytoin dose may be removed by CVVH, and patients may require higher than expected empiric doses. Phenytoin concentrations should be closely monitored in critically ill patients receiving CVVH.
Collapse
|
43
|
Sadeghi K, Hadi F, Ahmadi A, Hamishehkar H, Beigmohammadi MT, Mahmoodpoor A, Rouini MR, Farhudi S, Hendoui N, Najafi A, Mojtahedzadeh M. Total Phenytoin concentration is not well correlated with active free drug in critically-ill head trauma patients. J Res Pharm Pract 2014; 2:105-9. [PMID: 24991615 PMCID: PMC4076917 DOI: 10.4103/2279-042x.122376] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Objective: Phenytoin is an antiepileptic drug used widely for prophylaxis and treatment of seizure after neurotrauma. Phenytoin has a complex pharmacokinetics and monitoring of its serum concentrations is recommended during treatment. Total phenytoin concentration is routinely measured for monitoring of therapy. In this study, we evaluated the correlation between phenytoin total and free concentrations in neurotrauma critically-ill patients to determine whether the phenytoin total concentration is a reliable predictor of free drug, which is responsible for the therapeutic effects. Methods: A total of 40 adult head trauma patients evaluated for free (unbound) and total serum phenytoin concentrations. Patients were divided into two groups. Group A consists of 20 unconscious patients with severe head injury under mechanical ventilation and Group B consists of 20 conscious self-ventilated patients. Correlation and agreement between total and free phenytoin plasma concentrations were analyzed. Findings: Pearson correlation analysis and Bland-Altman test showed weak to moderate correlation (r = 0.528) and poor agreement between free and total phenytoin concentrations in patients with severe trauma and higher Acute Physiology And Chronic Health Evaluation II (APACHE II) scores (Group A) and good correlation (r = 0.817) and moderate agreement in patients with mild to moderate trauma and lower APACHE II scores (Group B). Conclusion: Our results indicated that total phenytoin serum concentration is not a reliable therapeutic goal for drug monitoring in severely-ill head trauma patients even in the absence of hypoalbuminemia, renal and hepatic failure. It seems justifiable to measure free phenytoin concentration in all severely ill neurotrauma patients.
Collapse
Affiliation(s)
- Kourosh Sadeghi
- Department of Clinical Pharmacy, Tehran University of Medical Sciences, Tehran, Iran
| | - Farin Hadi
- Department of Clinical Pharmacy, Islamic Azad University, Tehran, Iran
| | - Arezoo Ahmadi
- Department of Anesthesia and Intensive Care, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran
| | - Hadi Hamishehkar
- Department of Clinical Pharmacy and Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Mohammad-Taghi Beigmohammadi
- Department of Anesthesia and Intensive Care, Imam-Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran
| | - Ata Mahmoodpoor
- Department of Anesthesia and Intensive Care, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Mohammad Reza Rouini
- Department of Biopharmaceutics and Pharmacokinetics, Tehran University of Medical Sciences, Tehran, Iran
| | - Shirin Farhudi
- Students' Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Narjes Hendoui
- Department of Clinical Pharmacy, Mazandaran University of Medical Sciences, Sari, Iran
| | - Atabak Najafi
- Department of Anesthesia and Intensive Care, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran
| | - Mojtaba Mojtahedzadeh
- Department of Clinical Pharmacy, Tehran University of Medical Sciences, Tehran, Iran ; Department of Anesthesia and Intensive Care, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran
| |
Collapse
|
44
|
Tacker DH, Robinson R, Perrotta PL. Abbott ARCHITECT iPhenytoin assay versus similar assays for measuring free phenytoin concentrations. Lab Med 2014; 45:176-81. [PMID: 24869001 DOI: 10.1309/lm28b9dsrjcbcwwj] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
OBJECTIVE To measure free phenytoin (FP) concentrations in filtered specimens using the Abbott ARCHITECT iPhenytoin assay and to compare results from this method with results from the Abbott TDx/FLx assays. METHODS We verified accuracy, analytic measurement range, and precision for FP measurements. For correlation and therapeutic interval studies, we used filtered calibrators, controls, proficiency-testing materials, and surplus clinical samples. After implementation, we determined proficiency testing results. RESULTS The analytic measurement range was 2.0 to 25.0 micromol/L. Quality control materials (6.1, 12.6, and 20.1 micromol/L) provided mean (SD) recoveries of 96.1 (5.0%), 99.2 (5.0%), and 99.3 (5.7%), respectively, and coefficients of variation of 5.2%, 5.0%, and 5.8%, respectively. Clinical specimens produced mean (SD) FP recovery levels of 103.7 (10.6%) (bias, 0.1 [0.3] micromol/L). Altering the FP therapeutic range (4.0-8.0 micromol/L) was unnecessary. Proficiency testing yielded consistently acceptable results. CONCLUSION Our accuracy, precision, and correlation results were similar for the TDx/FLx and ARCHITECT assays, which demonstrates that the ARCHITECT iPhenytoin assay is acceptable for clinical FP measurements.
Collapse
|
45
|
Imam SH, Landry K, Kaul V, Gambhir H, John D, Kloss B. Free phenytoin toxicity. Am J Emerg Med 2014; 32:1301.e3-4. [PMID: 24768668 DOI: 10.1016/j.ajem.2014.03.036] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 03/22/2014] [Indexed: 10/25/2022] Open
Abstract
Phenytoin has a narrow therapeutic window, and when managing cases of toxicity, clinicians are very wary of this fact. Typically, if patient presents with symptoms suggestive of phenytoin toxicity, total serum phenytoin is promptly ordered. That could be falsely low especially in elderly or critically ill patients, which may lead to a low albumin level resulting in this discrepancy. The free phenytoin can be best estimated using the Sheiner-Tozer equation. Herein, we describe a case of an elderly male patient who presented with drowsiness, gait changes, and elevated liver enzymes and a normal total serum phenytoin level of 18 ng/dL (normal, 10-20 ng/dL).After taking his albumin level into account, his free phenytoin level was calculated to be 27 ng/dL, and the phenytoin was discontinued leading to resolution of his symptoms as well as a return of his liver function panel values to baseline.
Collapse
Affiliation(s)
- Syed Haider Imam
- Department of Internal Medicine, SUNY Upstate, Syracuse, NY, USA.
| | - Kristen Landry
- Department of Internal Medicine, SUNY Upstate, Syracuse, NY, USA
| | - Viren Kaul
- Department of Internal Medicine, SUNY Upstate, Syracuse, NY, USA
| | - Harvir Gambhir
- Department of Internal Medicine, SUNY Upstate, Syracuse, NY, USA
| | - Dinesh John
- Department of Internal Medicine, Syracuse Veterans Affairs Medical Center, Syracuse, NY, USA
| | - Brian Kloss
- Department of Internal Medicine, Syracuse Veterans Affairs Medical Center, Syracuse, NY, USA
| |
Collapse
|
46
|
Torbic H, Forni AA, Anger KE, Degrado JR, Greenwood BC. Use of antiepileptics for seizure prophylaxis after traumatic brain injury. Am J Health Syst Pharm 2014; 70:759-66. [PMID: 23592358 DOI: 10.2146/ajhp120203] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
PURPOSE Antiepileptics used for seizure prophylaxis after traumatic brain injury (TBI) are reviewed. SUMMARY Of the 275,000 people who are hospitalized with TBI each year, approximately 5-7% experience a posttraumatic seizure (PTS). According to the latest guidelines issued by the Brain Trauma Foundation and the American Academy of Neurology (AAN) for the management of severe TBI, PTS prophylaxis is recommended only during the first seven days after TBI. Of the available antiepileptic drugs, phenytoin has been the most extensively studied for the prophylaxis of PTS. Phenobarbital, valproate, and carbamazepine have not been as extensively researched, and, given their adverse-effect profiles and pharmacodynamic properties, there is no advantage to using these agents over phenytoin. Levetiracetam has demonstrated comparable efficacy to phenytoin for PTS prophylaxis and is associated with fewer adverse effects and monitoring considerations; it may be a reasonable alternative to phenytoin. However, levetiracetam has been associated with an increased seizure tendency. The Brain Trauma Foundation recommends using phenytoin for early PTS prophylaxis. The guidelines also state that valproate has demonstrated similar efficacy to phenytoin but warn that its use may be associated with increased mortality. CONCLUSION The available literature supports the use of antiepileptics for early PTS prophylaxis during the first week after a TBI. Phenytoin has been extensively studied for this indication and is recommended by the AAN and Brain Trauma Foundation guidelines for early PTS prophylaxis. Levetiracetam has demonstrated comparable efficacy to phenytoin for early PTS prophylaxis and may be a reasonable alternative to consider in this patient population.
Collapse
Affiliation(s)
- Heather Torbic
- Critical Care, Brigham and Women's Hospital, Boston, MA 02115, USA.
| | | | | | | | | |
Collapse
|
47
|
Current and Future Status of Therapeutic Drug Monitoring in the Treatment of IBD. ACTA ACUST UNITED AC 2014; 12:76-89. [DOI: 10.1007/s11938-013-0005-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
|
48
|
Sirich TL, Funk BA, Plummer NS, Hostetter TH, Meyer TW. Prominent accumulation in hemodialysis patients of solutes normally cleared by tubular secretion. J Am Soc Nephrol 2013; 25:615-22. [PMID: 24231664 DOI: 10.1681/asn.2013060597] [Citation(s) in RCA: 107] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Dialytic clearance of urea is efficient, but other small solutes normally secreted by the kidney may be cleared less efficiently. This study tested whether the high concentrations of these solutes in hemodialysis patients reflect a failure of passive diffusion methods to duplicate the efficacy of clearance by tubular secretion. We compared the plasma concentrations and clearance rates of four solutes normally cleared by tubular secretion with the plasma concentrations and clearance rates of urea and creatinine in patients receiving maintenance hemodialysis and normal subjects. The predialysis concentrations (relative to normal subjects) of unbound phenylacetylglutamine (122-fold), hippurate (108-fold), indoxyl sulfate (116-fold), and p-cresol sulfate (41-fold) were much greater than the concentrations of urea (5-fold) and creatinine (13-fold). The dialytic clearance rates (relative to normal subjects) of unbound phenylacetylglutamine (0.37-fold), hippurate (0.16-fold), indoxyl sulfate (0.21-fold), and p-cresol sulfate (0.39-fold) were much lower than the rates of urea (4.2-fold) and creatinine (1.3-fold). Mathematical modeling showed that prominent accumulation of the normally secreted solutes in hemodialysis patients could be accounted for by lower dialytic clearance relative to physiologic clearance combined with the intermittency of treatment. Whether or not more efficient removal of normally secreted solutes improves outcomes in dialysis patients remains to be tested.
Collapse
Affiliation(s)
- Tammy L Sirich
- Department of Medicine, Veterans Affairs Palo Alto Healthcare System and Stanford University, Palo Alto, California; and
| | | | | | | | | |
Collapse
|
49
|
Empey PE, Velez de Mendizabal N, Bell MJ, Bies RR, Anderson KB, Kochanek PM, Adelson PD, Poloyac SM. Therapeutic hypothermia decreases phenytoin elimination in children with traumatic brain injury. Crit Care Med 2013; 41:2379-87. [PMID: 23896831 PMCID: PMC3783553 DOI: 10.1097/ccm.0b013e318292316c] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Preclinical and clinical studies have suggested that therapeutic hypothermia, while decreasing neurologic injury, may also lead to drug toxicity that may limit its benefit. Cooling decreases cytochrome P450 (CYP)-mediated drug metabolism, and limited clinical data suggest that drug levels are elevated. Fosphenytoin is metabolized by cytochrome P450 2C, has a narrow therapeutic range, and is a commonly used antiepileptic medication. The objective of this study was to evaluate the impact of therapeutic hypothermia on phenytoin levels and pharmacokinetics in children with severe traumatic brain injury. DESIGN Pharmacokinetic analysis of subjects participating in a multicenter randomized phase III study of therapeutic hypothermia for severe traumatic brain injury. SETTING ICU at the Children's Hospital of Pittsburgh. PATIENTS Nineteen children with severe traumatic brain injury. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS A sum of 121 total and 114 free phenytoin levels were evaluated retrospectively in 10 hypothermia-treated and nine normothermia-treated children who were randomized to 48 hours of cooling to 32-33°C followed by slow rewarming or controlled normothermia. Drug dosing, body temperatures, and demographics were collected during cooling, rewarming, and posttreatment periods (8 d). A trend toward elevated free phenytoin levels in the hypothermia group (p=0.051) to a median of 2.2 mg/L during rewarming was observed and was not explained by dosing differences. Nonlinear mixed-effects modeling incorporating both free and total levels demonstrated that therapeutic hypothermia specifically decreased the time-variant component of the maximum velocity of phenytoin metabolism (Vmax) 4.6-fold (11.6-2.53 mg/hr) and reduced the overall Vmax by ~50%. Simulations showed that the increased risk for drug toxicity extends many days beyond the end of the cooling period. CONCLUSIONS Therapeutic hypothermia significantly reduces phenytoin elimination in children with severe traumatic brain injury leading to increased drug levels for an extended period of time after cooling. Pharmacokinetic interactions between hypothermia and medications should be considered when caring for children receiving this therapy.
Collapse
Affiliation(s)
- Philip E Empey
- 1Department of Pharmacy and Therapeutics, Center for Clinical Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA. 2Division of Clinical Pharmacology, School of Medicine and Indiana Clinical and Translational Sciences Institute, Indiana University, Indianapolis, IN. 3Department of Critical Care Medicine, School of Medicine, and the Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, PA. 4Department of Neurological Surgery, School of Medicine, and the Safar Center for Resuscitation Research, University of Pittsburgh, Pittsburgh, PA. 5Department of Pharmaceutical Sciences, Center for Clinical Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA. 6Division of Neurosurgery/Children's Neuroscience, Department of Child Health, Barrow Neurological Institute, Phoenix Children's Hospital, Phoenix, AZ
| | | | | | | | | | | | | | | |
Collapse
|
50
|
Putt MT, Udy AA, Jarrett P, Martin J, Hennig S, Salmon N, Lipman J, Roberts JA. Phenytoin loading doses in adult critical care patients: does current practice achieve adequate drug levels? Anaesth Intensive Care 2013; 41:602-9. [PMID: 23977911 DOI: 10.1177/0310057x1304100505] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Phenytoin is regularly employed in the critically ill for prophylaxis against or treatment of seizure disorders. No prior studies have examined current dosing practices in an Australasian intensive care unit (ICU) setting. The aims of this study were to: a) describe the adequacy of contemporary dosing in respect to free and total serum phenytoin concentrations; b) identify factors associated with therapeutic drug concentrations; and c) examine the accuracy of predictive equations that estimate free concentrations in this setting. All patients receiving a loading dose of phenytoin in a tertiary-level ICU were eligible for enrolment; 53 patients were enrolled in the study. Serum samples to determine free and total phenytoin concentrations (measured by high performance liquid chromatography) were then drawn prior to the following dose. Free concentrations below the recommended target (<1 mg/l) were considered as suboptimal. The most common indication for phenytoin loading was traumatic brain injury (49%) and the mean administered dose was 14.5 (3.66) mg/kg. Twenty-six patients (49%) had suboptimal trough free concentrations, although this subgroup was significantly heavier and therefore received a lower per kilogram dose (12.8 [3.1] vs 16.3 [3.4] mg/kg, P=0.001). In multivariate analysis, larger weight adjusted doses (P=0.018), higher albumin concentration (P=0.034) and receiving phenytoin for an indication other than seizure (P=0.035), were associated with a greater likelihood of adequate concentrations. In conclusion, phenytoin dosing remains complex in critically ill patients, although lower per kilogram loading doses are strongly associated with free concentrations below the desired target.
Collapse
Affiliation(s)
- M T Putt
- Department of Intensive Care Medicine, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia
| | | | | | | | | | | | | | | |
Collapse
|