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Pretorius E, van Zyl P, Joubert G. Therapeutic drug monitoring for valproate: deriving a novel formula for calculation of free concentration. Eur J Clin Pharmacol 2024:10.1007/s00228-024-03741-2. [PMID: 39150536 DOI: 10.1007/s00228-024-03741-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2024] [Accepted: 08/08/2024] [Indexed: 08/17/2024]
Abstract
BACKGROUND Monitoring free valproate concentrations, as with other highly protein-bound anticonvulsants, is essential in clinical situations where protein binding may be disrupted. Conversion of measured total concentrations to approximate free concentrations offers a cost-effective alternative. This study evaluated the relationship between total and free valproate concentrations for discordance and the impact of key determinants. A novel formula was devised that incorporates significant variables. METHODS A multicentre, cross-sectional observational analytical study included 101 subjects 18 years and older using valproate for 6 months or longer. Participants were recruited from private and public sector healthcare settings from primary to tertiary level in, South Africa, during 2017-2019. RESULTS Free valproate concentrations could be measured for 84 subjects. Discordance for concomitant total and free valproate concentrations was 79.1%. Among 19 participants with elevated free concentrations, 15 (78.9%) had total valproate concentrations within the recommended reference range. Calculations based on the study-derived formula were more accurate in predicting free valproate concentration than previously proposed methods. CONCLUSION This study proposes that the novel formula for calculating free valproate enables more accurate prediction.
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Affiliation(s)
- Erna Pretorius
- Department of Pharmacology, Faculty of Health Sciences, University of the Free State, Bloemfontein, South Africa.
| | - Paulina van Zyl
- Department of Pharmacology, Faculty of Health Sciences, University of the Free State, Bloemfontein, South Africa
| | - Gina Joubert
- Department of Biostatistics, Faculty of Health Sciences, University of the Free State, Bloemfontein, South Africa
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2
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Conde Giner S, Belles Medall MD, Ferrando Piqueres R. Design and validation of a predictive equation to estimate unbound valproic acid concentration. Eur J Hosp Pharm 2023; 30:293-296. [PMID: 34750247 PMCID: PMC10447952 DOI: 10.1136/ejhpharm-2021-003092] [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: 10/04/2021] [Accepted: 10/25/2021] [Indexed: 11/03/2022] Open
Abstract
OBJECTIVES Total plasma levels of valproic acid (VPA) may mask an increased risk of adverse effects in hypoalbuminaemic patients since, in these patients, the free fraction is higher. The aim of this study is to analyse the relationship between plasma levels of total and free VPA (FVPA) in hypoalbuminaemic patients and define an equation that allows the estimation of FVPA concentration, as well as to validate the obtained equation. METHODS This is a retrospective observational study conducted between January 2015 and January 2020. Hypoalbuminaemic adult patients with normal renal function were included. Serum VPA levels were determined using an automated enzyme immunoassay technique with a pre-treatment of the sample by ultrafiltration for the quantification of FVPA. Patients' determinations were randomised into two groups: first, to calculate the FVPA estimation equation (regression group) by multiple linear regression analysis; and second to validate the equation (validation group), calculating the agreement between experimental and estimated FVPA concentrations using Lin's coefficient and a Bland and Altman analysis. RESULTS We included 51 determinations, corresponding to 33 patients: 26 in the regression group, and 25 in the validation group. The multiple linear regression analysis showed a statistically significant relationship between FVPA concentration (Y), total VPA concentration (X1) and albumin level (X2), explained by the equation Y=11.882 + 0.216*X1-4.722*X2. Pearson's correlation coefficient was 0.798 (p<0.001). Lin's coefficient was 0.82 (95% CI 0.63 to 0.92). The Bland and Altman analysis showed a bias of 0.32 mg/L, and the concordance limits were between -3.80 and 4.44. CONCLUSIONS The calculated equation adequately predicts FVPA concentration, with a high degree of correlation between the variables. Despite Lin's coefficient outcome, Bland and Altman analysis showed a minimum bias that slightly underestimates FVPA concentration, positioning the calculated equation as a useful and validated estimation tool in hypoalbuminaemic patients with normal renal function.
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Affiliation(s)
- Silvia Conde Giner
- Pharmacy Department, Hospital General de Castellón, Castellon de la Plana, Spain
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3
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A novel method for predicting the unbound valproic acid concentration. Drug Metab Pharmacokinet 2023; 50:100503. [PMID: 37080137 DOI: 10.1016/j.dmpk.2023.100503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 01/26/2023] [Accepted: 03/02/2023] [Indexed: 03/07/2023]
Abstract
In this study, we constructed a prediction formula for unbound valproic acid (VPA) concentration that was more accurate and widely applicable than previously reported formulae. A total of 136 datasets from 75 patients were analyzed retrospectively. The median of free fraction of VPA was 0.16 (interquartile range: 0.07; range: 0.07-0.45). The parameter that combined total VPA concentration (CtVPA) and serum albumin (SA), (CtVPA [μM] - 2 × SA [μM]), was significantly related to the free fraction of VPA (r = 0.76, p < 0.001). We constructed a combined parameter-based prediction formula for unbound VPA concentration. Analysis using external datasets from patients without severe renal failure showed that the prediction errors of the unbound VPA concentration were lower than those of previously reported formulae. Although the previous formulae showed large prediction errors, especially in the specific range of CtVPA values, the constructed formula showed a weak trend with CtVPA or SA. The formula based on (CtVPA [μM] - 2 × SA [μM]) had high prediction accuracy and wide applicability in predicting the unbound VPA concentration in patients without severe renal failure.
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Lin K, Cao VFS, Au C, Dahri K. Clinical Pharmacokinetic Monitoring of Free Valproic Acid Levels: A Systematic Review. Clin Pharmacokinet 2022; 61:1345-1363. [PMID: 36040614 DOI: 10.1007/s40262-022-01171-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/07/2022] [Indexed: 11/03/2022]
Abstract
BACKGROUND Current guidelines recommend therapeutic drug monitoring as a critical component of valproic acid (VPA) therapy. Due to high protein binding, the active unbound (free) portion of VPA can be misrepresented by total VPA serum levels in certain clinical scenarios. Monitoring free VPA serum levels may be warranted when assessing the clinical response to VPA therapy. OBJECTIVES The aims were to conduct a systematic review to identify a therapeutic range for free VPA serum levels; to explore the correlation of free VPA serum levels with clinical toxicity and therapeutic benefit; and to examine predictors of discordance between free and total VPA levels. METHODS Medline, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), PsycINFO, BIOSIS Previews, and Cumulative Index to Nursing and Allied Health Literature (CINAHL) were searched from the time of database inception to June 20, 2021. Randomized controlled trials and observational studies that evaluated any patient receiving VPA with free VPA level monitoring were included. RESULTS Of 189 citations, we identified 27 relevant studies, which included 14 observational studies, two case series, and 11 case reports. Three studies provided a therapeutic range for free VPA levels between 20 and 410 μmol/L. Two studies suggested the occurrence of hyperammonemia and thrombocytopenia at free VPA serum levels above 60 µmol/L and 103.3 µmol/L, respectively. Two studies suggested an upper limit for neurotoxicity at free VPA serum levels of 70 µmol/L and 207.9 µmol/L. Hypoalbuminemia was identified as a predictor of therapeutic discordance. CONCLUSIONS This review demonstrates a paucity of data informing the clinical utility of free VPA serum levels. Further high-quality trials are needed to validate an optimal therapeutic range for free VPA levels.
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Affiliation(s)
- Kevin Lin
- University of British Columbia, Faculty of Pharmaceutical Sciences, Vancouver, BC, Canada
| | - Vivien F S Cao
- Department of Pharmacy, Vancouver General Hospital, Vancouver, BC, Canada.
| | - Charles Au
- Lower Mainland Pharmacy Services, Vancouver, BC, Canada
| | - Karen Dahri
- University of British Columbia, Faculty of Pharmaceutical Sciences, Vancouver, BC, Canada.,Department of Pharmacy, Vancouver General Hospital, Vancouver, BC, Canada
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5
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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.
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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
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Sangüesa E, Cirujeda C, Concha J, Padilla PP, García CB, Ribate MP. Pharmacokinetic interactions between clozapine and valproic acid in patients with treatment-resistant schizophrenia: Does UGT polymorphism affect these drug interactions? Chem Biol Interact 2022; 364:110042. [PMID: 35853541 DOI: 10.1016/j.cbi.2022.110042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Accepted: 07/13/2022] [Indexed: 11/29/2022]
Abstract
The combination of valproic acid (VPA) and clozapine (CLZ) is regularly prescribed for augmentation therapy in treatment resistant schizophrenia. The VPA has been shown to reduce norclozapine (NCLZ) plasma levels, but the mechanism of this interaction remains unknown. The aim of this study is to examine the differences between patients treated with CLZ and patients treated with CLZ plus VPA. For it, various factors have been evaluated. The study was based on plasma samples from CLZ and CLZ plus VPA treated patients (n = 61) subjected to routine therapeutic drug monitoring considering clinical data, smoking status, daily dose of CLZ and VPA, concomitant medications, albumin, and renal and hepatic function. Genotyping of polymorphisms of CYP1A2, CYP3A4/5, CYP2C19, ABCB1, UGT2B10 and CYP2C19 were performed by real time PCR. CYP2D6 were genotyped using competitive allele-specific PCR and by a long PCR based method. Plasma CLZ and NCLZ concentrations were measured by Liquid Chromatography-Tandem masses (LC-MS/MS) and plasma VPA by Ultraviolet-Visible (UV-vis) spectrophotometric immunoassay. The patients presented adequate CLZ levels in relation to the dose. However, NCLZ levels were excessively low and the CLZ/NCLZ ratio very high. Patients with UGT2B10 GT (rs61750900) genotype showed lower NCLZ plasma levels and C/D NCLZ, and higher CLZ/NCLZ ratio versus patients with UGT2B10 GG genotype. VPA, smoking, the presence of UGT2B10 GT genotype and having low albumin levels indicate that the CLZ/NCLZ ratio is affected, mostly coinciding with decreased NCLZ levels and possibly with an increased risk of neutropenia.
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Affiliation(s)
- Estela Sangüesa
- Faculty of Health Sciences, Universidad San Jorge, Villanueva de Gállego- Zaragoza, Spain
| | - Christine Cirujeda
- Centro Neuropsiquiátrico Nuestra Señora del Carmen, Hermanas Hospitalarias, Zaragoza, Spain
| | - Julia Concha
- Faculty of Health Sciences, Universidad San Jorge, Villanueva de Gállego- Zaragoza, Spain
| | - Pedro Pablo Padilla
- Centro Neuropsiquiátrico Nuestra Señora del Carmen, Hermanas Hospitalarias, Zaragoza, Spain
| | - Cristina Belén García
- Faculty of Health Sciences, Universidad San Jorge, Villanueva de Gállego- Zaragoza, Spain.
| | - María Pilar Ribate
- Faculty of Health Sciences, Universidad San Jorge, Villanueva de Gállego- Zaragoza, Spain
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Bennett S, Shad MU. Valproic acid autoinduction: a case-based review. Int J Bipolar Disord 2021; 9:27. [PMID: 34468892 PMCID: PMC8408294 DOI: 10.1186/s40345-021-00232-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 07/29/2021] [Indexed: 11/10/2022] Open
Abstract
Although valproic acid (VPA) induces the metabolism of multiple other drugs, the clinical reports of VPA autoinduction are rare. A comprehensive literature search yielded only one published case series, which provided the rationale to conduct a review of the published cases along with a new case of VPA autoinduction. Although there may be myriad of reasons for lack of published cases of VPA autoinduction, potential underreporting may be one of the core reasons. Lack of understanding into the highly complex metabolism of VPA may also make it difficult to recognize and report VPA autoinduction. However, it is important to mention that in addition to autoinduction increased elimination of VPA may be mediated by several pharmacokinetic (PK) factors, such as drug interactions, genetic polymorphisms of metabolic enzymes, and protein displacement reactions. As VPA is metabolized by multiple metabolic pathways, the risk for drug interactions is relatively high. There is also a growing evidence for high genetic inducibility of some enzymes involved in VPA metabolism. Protein displacement reactions with VPA increase the biologically active and readily metabolizable free fraction and pose a diagnostic challenge as they are usually not requested by most clinicians. Thus, monitoring of free fraction with total VPA levels may prevent clinically serious outcomes and optimize VPA treatment in clinically challenging patients. This case-based review compares the clinical data from three published cases and a new case of VPA autoinduction to enhance clinicians' awareness of this relatively rare but clinically relevant phenomenon along with a discussion of potential underlying mechanisms.
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Affiliation(s)
| | - Mujeeb U Shad
- University of Nevada Las Vegas, Las Vegas, NV, USA. .,Touro University Nevada, Las Vegas, NV, USA. .,Valley Health System, Las Vegas, NV, USA.
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8
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Madan A, Donovan PJ, Risetto T, Trenerry H, Lander CM. Monitoring for valproate and phenytoin toxicity in hypoalbuminaemia: A retrospective cohort study. Br J Clin Pharmacol 2021; 87:4341-4353. [PMID: 33835518 DOI: 10.1111/bcp.14853] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 03/14/2021] [Accepted: 03/31/2021] [Indexed: 11/28/2022] Open
Abstract
AIMS Equations to calculate albumin-adjusted total concentrations have been validated to correlate with measured free concentrations for both phenytoin and valproate, but there is a lack of data to assess correlation with clinical outcomes. We aimed to assess the association of hypoalbuminaemia and albumin-adjusted total concentrations with concentration-dependent toxicity for phenytoin and valproate and review the impact on management decisions following concentration monitoring in hypoalbuminaemia. METHODS Patients undergoing concentration monitoring for phenytoin or valproate between January and December 2018 were included. Patients were identified using a centralised laboratory database with data extracted from medical records. RESULTS Total phenytoin concentrations were measured for 144 patients, with hypoalbuminaemia (≤30 g L-1 ) recorded in 59 (41%) patients. Albumin-adjusted phenytoin concentration >20 mg L-1 was associated with increased neurological adverse effects (77% vs. 43%, P < .001). On logistic regression, higher albumin-adjusted phenytoin concentration was an independent risk factor for neurotoxicity (OR 1.06, 95% CI 1.01-1.12, P = .011). Total valproate concentrations were measured for 383 patients, with hypoalbuminaemia (≤30 g L-1 ) noted in 53 (14%) patients. For the valproate cohort, hypoalbuminaemia (42% vs. 28%, P = .039) and albumin-adjusted valproate concentration >100 mg L-1 (49% vs. 23%, P < .001) were both associated with increased neurotoxicity. On multiple logistic-regression, valproate daily dose (aOR = 1.01, 95% CI 1.00-1.02, P = .006) and albumin-adjusted valproate concentration (aOR 1.01, 95% CI 1.00-1.02, P = .033) were independent risk factors for neurotoxicity after accounting for confounders. CONCLUSION While measuring free drug concentrations in hypoalbuminaemia would be ideal, the adjustment equations can help identify vulnerable patients needing further assessment of potential concentration-dependent toxicity.
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Affiliation(s)
- Arushi Madan
- Clinical Pharmacology, Royal Brisbane & Women's Hospital, Brisbane, Australia.,Faculty of Medicine, University of Queensland, Brisbane, Australia
| | - Peter J Donovan
- Clinical Pharmacology, Royal Brisbane & Women's Hospital, Brisbane, Australia.,Faculty of Medicine, University of Queensland, Brisbane, Australia
| | - Tracy Risetto
- Queensland Medicines Advice and Information Service, Royal Brisbane & Women's Hospital, Brisbane, Australia
| | - Helen Trenerry
- Queensland Medicines Advice and Information Service, Royal Brisbane & Women's Hospital, Brisbane, Australia
| | - Cecilie M Lander
- Faculty of Medicine, University of Queensland, Brisbane, Australia.,Neurology, Royal Brisbane & Women's Hospital, Brisbane, Australia
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[S2k guidelines: status epilepticus in adulthood : Guidelines of the German Society for Neurology]. DER NERVENARZT 2021; 92:1002-1030. [PMID: 33751150 PMCID: PMC8484257 DOI: 10.1007/s00115-020-01036-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Accepted: 11/17/2020] [Indexed: 01/16/2023]
Abstract
This S2k guideline on diagnosis and treatment of status epilepticus (SE) in adults is based on the last published version from 2021. New definitions and evidence were included in the guideline and the clinical pathway. A seizures lasting longer than 5 minutes (or ≥ 2 seizures over more than 5 mins without intermittend recovery to the preictal neurological state. Initial diagnosis should include a cCT or, if possible, an MRI. The EEG is highly relevant for diagnosis and treatment-monitoring of non-convulsive SE and for the exclusion or diagnosis of psychogenic non-epileptic seizures. As the increasing evidence supports the relevance of inflammatory comorbidities (e.g. pneumonia) related clinical chemistry should be obtained and repeated over the course of a SE treatment, and antibiotic therapy initiated if indicated.Treatment is applied on four levels: 1. Initial SE: An adequate dose of benzodiazepine is given i.v., i.m., or i.n.; 2. Benzodiazepine-refractory SE: I.v. drugs of 1st choice are levetiracetam or valproate; 3. Refractory SE (RSE) or 4. Super-refractory SE (SRSE): I.v. propofol or midazolam alone or in combination or thiopental in anaesthetic doses are given. In focal non-convulsive RSE the induction of a therapeutic coma depends on the circumstances and is not mandatory. In SRSE the ketogenic diet should be given. I.v. ketamine or inhalative isoflorane can be considered. In selected cased electroconvulsive therapy or, if a resectable epileptogenic zone can be defined epilepsy surgery can be applied. I.v. allopregnanolone or systemic hypothermia should not be used.
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Wang D, Champion-Lyons E, Neyens R, Bohm N, Caddell B, Babic N. The Effect of Sample Handling on Free Valproic Acid Levels. J Appl Lab Med 2020; 6:645-653. [PMID: 33249432 DOI: 10.1093/jalm/jfaa181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 09/09/2020] [Indexed: 11/13/2022]
Abstract
BACKGROUND Valproic acid (VPA) is a broad-spectrum anticonvulsant drug. Under normal conditions, this drug is highly protein bound. However, in patients with hypoalbuminemia, the free fraction can increase substantially while the total VPA levels remain in therapeutic range. The neurologic activity and toxicity of the drug are directly related to free drug levels. METHODS Our in-house free VPA assay was validated using 20 patient samples obtained from a reference laboratory (RL1). It was further evaluated by parallel testing with RL1 using samples collected from our patients. Subsequently, sample handling effects were investigated by comparing free VPA levels measured in our laboratory to 3 selected RLs with different sample transportation conditions. RESULTS No significant bias was observed between the in-house assay (y) and RL1 (x) assay in free VPA measurement (y = 1.12x + 0.072, r = 0.994). However, patient samples collected in our institution and sent to RL1 revealed significant negative bias (y = 0.776x - 3.861, r = 0.954). A large discrepancy in free VPA levels was further observed from identical aliquots of the same samples transported to 3 RLs in different conditions. CONCLUSIONS Our study demonstrated that sample handling has significant impact on free VPA levels. The observed magnitude of variation exceeds a clinically acceptable limit and could alter clinical decisions.
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Affiliation(s)
- Dan Wang
- Department of Pathology and Laboratory Medicine, Beaumont Health, Royal Oak, MI 48073, USA
| | - Elizabeth Champion-Lyons
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Ron Neyens
- Department of Pharmacy, Medical University of South Carolin, Charleston, SC 29425, USA
| | - Nicole Bohm
- Department of Pharmacy, Medical University of South Carolin, Charleston, SC 29425, USA
| | - Brittany Caddell
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Nikolina Babic
- Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC 29425, USA
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Fisch U, Baumann SM, Semmlack S, Marsch S, Rüegg S, Sutter R. Accuracy of Calculated Free Valproate Levels in Adult Patients With Status Epilepticus. Neurology 2020; 96:e102-e110. [PMID: 33055270 DOI: 10.1212/wnl.0000000000011000] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 08/20/2020] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE To test the accuracy of an equation in adult patients with status epilepticus that calculates the free concentration of serum valproic acid (fVPA) from the total concentration of serum valproic acid (tVPA) and serum albumin. METHODS All adult patients with status epilepticus who were treated at a Swiss academic medical center between 2005 and 2018 with concurrent measurements of tVPA, fVPA, and serum albumin were included. fVPA was categorized as subtherapeutic, therapeutic (5-10 mg/L), or supratherapeutic. Agreement was defined as the proportion of measured and calculated fVPA falling within the same category. RESULTS Of 676 patients with status epilepticus, 104 had 506 measurements, with a median of 3 (interquartile range [IQR] 1.5-6.5) per patient. The median tVPA was 43.5 mg/L (27.4-63.6), with measured fVPA 9.1 mg/L (4.5-14.7) and calculated fVPA 10.1 mg/L (7.0-13.0), respectively. The median deviation of calculated from measured fVPA was -0.8 mg/L (-3.2 to 2.5) with 336 measurements >1 mg/L. While the association between measured and calculated fVPA was linear (regression coefficient 1.1, 95% confidence interval 0.9-1.2, p < 0.0001), the agreement on effective drug levels did not match in 39.8% of measurements regardless of serum albumin levels, with calculated fVPA overestimating measured fVPA in 30.4%. tVPA and serum albumin independently influenced the accuracy of the calculated fVPA in the multivariable model. CONCLUSIONS Calculated fVPA is inaccurate when using the proposed equation in adult patients with status epilepticus, calling for drug monitoring based on measured fVPA in this context.
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Affiliation(s)
- Urs Fisch
- From the Department of Neurology (U.F., S.R.) and Clinic for Intensive Care Medicine (S.M.B., S.S., S.M., R.S.), University Hospital Basel; and Medical Faculty of the University of Basel (S.M., S.R., R.S.), Switzerland.
| | - Sira M Baumann
- From the Department of Neurology (U.F., S.R.) and Clinic for Intensive Care Medicine (S.M.B., S.S., S.M., R.S.), University Hospital Basel; and Medical Faculty of the University of Basel (S.M., S.R., R.S.), Switzerland
| | - Saskia Semmlack
- From the Department of Neurology (U.F., S.R.) and Clinic for Intensive Care Medicine (S.M.B., S.S., S.M., R.S.), University Hospital Basel; and Medical Faculty of the University of Basel (S.M., S.R., R.S.), Switzerland
| | - Stephan Marsch
- From the Department of Neurology (U.F., S.R.) and Clinic for Intensive Care Medicine (S.M.B., S.S., S.M., R.S.), University Hospital Basel; and Medical Faculty of the University of Basel (S.M., S.R., R.S.), Switzerland
| | - Stephan Rüegg
- From the Department of Neurology (U.F., S.R.) and Clinic for Intensive Care Medicine (S.M.B., S.S., S.M., R.S.), University Hospital Basel; and Medical Faculty of the University of Basel (S.M., S.R., R.S.), Switzerland
| | - Raoul Sutter
- From the Department of Neurology (U.F., S.R.) and Clinic for Intensive Care Medicine (S.M.B., S.S., S.M., R.S.), University Hospital Basel; and Medical Faculty of the University of Basel (S.M., S.R., R.S.), Switzerland
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12
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Factors to influence the accuracy of albumin adjusted free valproic acid concentration. J Formos Med Assoc 2020; 120:1114-1120. [PMID: 32978045 DOI: 10.1016/j.jfma.2020.09.004] [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: 05/11/2020] [Revised: 08/31/2020] [Accepted: 09/07/2020] [Indexed: 11/21/2022] Open
Abstract
BACKGROUND Therapeutic drug monitoring (TDM) is recommended during treatment with valproic acid (VPA), as is the measurement of free VPA concentration (MfVPA). However, MfVPA is unavailable in many institutions. Based on the highly protein-bound characteristics of VPA, an albumin-adjusted formula has been proposed to predict free VPA concentration (PfVPA). Nevertheless, the factors affecting the accuracy of this formula remain unknown, as does the concordance between MfVPA and PfVPA. METHODS Adult patients receiving VPA and undergoing TDM were enrolled. Free and total serum concentration (TVPA) were categorized as subtherapeutic, therapeutic, or supratherapeutic based on the reference range of 5-15 and 50-100 μg/mL, respectively. Concordance was defined as MfVPA and PfVPA, or MfVPA and TVPA, falling within the same category. Multivariate logistic regression with generalized estimating equation was adopted to identify factors affecting concordance, and the receiver operating characteristic curve was applied to determine the cutoff values of predictors. RESULTS A total of 98 data points from 51 participants were included for analysis. The concordance of MfVPA and PfVPA, and MfVPA and TVPA, was 72% and 44%, respectively. Blood urea nitrogen (BUN) (0.97 [0.95-0.99], P = 0.01) and TVPA (0.97 [0.95-0.99], P = 0.02) had a significant influence on the concordance of MfVPA and PfVPA. The cutoff values of TVPA and BUN for the accuracy of the albumin-adjusted formula were 56.4 μg/mL and 51.05 mg/dL, respectively. CONCLUSION If MfVPA is not available, the albumin-adjusted formula should be applied before VPA dosage adjustment when TVPA is < 56.4 μg/mL and BUN is < 51.05 mg/dL.
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Abstract
OBJECTIVES The purpose of this critical narrative review is to discuss common indications for ordering serum albumin levels in adult critically ill patients, evaluate the literature supporting these indications, and provide recommendations for the appropriate ordering of serum albumin levels. DATA SOURCES PubMed (1966 to August 2020), Cochrane Library, and current clinical practice guidelines were used, and bibliographies of retrieved articles were searched for additional articles. STUDY SELECTION AND DATA EXTRACTION Current clinical practice guidelines were the preferred source of recommendations regarding serum albumin levels for guiding albumin administration and for nutritional monitoring. When current comprehensive reviews were available, they served as a baseline information with supplementation by subsequent studies. DATA SYNTHESIS Serum albumin is a general marker of severity of illness, and hypoalbuminemia is associated with poor patient outcome, but albumin is an acute phase protein, so levels vacillate in critically ill patients in conjunction with illness fluctuations. The most common reasons for ordering serum albumin levels in intensive care unit (ICU) settings are to guide albumin administration, to estimate free phenytoin or calcium levels, for nutritional monitoring, and for severity-of-illness assessment. RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE Because hypoalbuminemia is common in the ICU setting, inappropriate ordering of serum albumin levels may lead to unnecessary albumin administration or excessive macronutrient administration in nutritional regimens, leading to possible adverse effects and added costs. CONCLUSIONS With the exception of the need to order serum albumin levels as a component of selected severity-of-illness scoring systems, there is little evidence or justification for routinely ordering levels in critically ill patients.
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Prediction of Serum-Free and Cerebrospinal Fluid Valproic Acid Levels in Patients With Hypoalbuminemia After Craniotomy. Ther Drug Monit 2020; 42:610-616. [DOI: 10.1097/ftd.0000000000000749] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Madan A, Risetto T, Ad QM, Ser I, Trenerry H, Donovan P. The perils of antiepileptic toxicity. Aust Prescr 2020; 43:61-63. [PMID: 32346213 PMCID: PMC7186274 DOI: 10.18773/austprescr.2020.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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VandenBerg A, Broadway J. Enteral administration of protein supplement and valproate: A potential pharmacokinetic interaction. Ment Health Clin 2018; 7:10-12. [PMID: 29955491 DOI: 10.9740/mhc.2017.01.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Background Valproic acid (VPA) and its derivatives are highly protein bound. Certain highly protein bound medications (eg, phenytoin) have specific administration instructions for patients on enteral nutrition supplements to optimize absorption of the medication. Pharmacokinetic interactions between VPA and enteral nutrition or protein supplements demonstrating impaired absorption have not been published to date. Case Report A patient receiving enteral VPA syrup via percutaneous endoscopic gastrostomy tube experienced a clinically significant decrease in serum concentration when enteral protein supplement was initiated. Other sources of interactions were ruled out, and VPA serum concentration increased when doses were separated from protein supplement by 2 hours. Discussion This is the first published case of enteral protein supplementation affecting absorption of enteral VPA. Enteral feeds are known to interact with other highly protein bound medications, and clinical practice for these medications may be used to guide administration when an interaction with VPA is suspected. Conclusion When using enteral protein supplements concomitantly with enteral VPA, clinicians may consider separating doses to avoid potential interaction or impaired absorption.
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Affiliation(s)
- Amy VandenBerg
- Adjunct Assistant Professor, Department of Clinical Pharmacy and Outcomes Sciences, Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, South Carolina,
| | - Jessica Broadway
- Assistant Professor, Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, South Carolina
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VandenBerg A, Broadway J, Lalich C, Kennedy R, Williams K. Valproate serum concentrations in patients with hypoalbuminemia and medical complications. Ment Health Clin 2018; 7:13-15. [PMID: 29955492 DOI: 10.9740/mhc.2017.01.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Introduction Valproic acid (VPA) and its derivatives are highly protein bound with free fraction increasing with dose and serum concentration. Consensus guidelines regarding dose adjustment for hypoalbuminemia are not available. Methods A literature search was performed using PubMed to identify articles with the following key terms: "valproate," "valproic acid," "protein binding," "albumin," and "hypoalbuminemia." We report our findings as well as 5 cases involving pharmacokinetic impact of hypoalbuminemia on valproate. Results A previously published model for normalizing VPA serum concentration for hypoalbuminemia in patients with epilepsy was compared to results for 5 cases (4 female, 1 male) in which VPA was used for psychiatric illness. Only 1 of the cases had free serum concentrations in the range that would be expected with the model. Free concentrations ranged from 22% to 83% with no clear relationship to other factors (weight, age, serum creatinine, or dose). Female patients with similar albumin had higher free fractions than the 1 male patient. Discussion Due to the variability in pharmacokinetic impact of hypoalbuminemia, it is important to monitor patients closely for signs of VPA toxicity in cases involving altered albumin levels. It would be prudent to use free serum VPA concentrations when patients experience fluctuations in albumin or have unexpected response to medication.
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Affiliation(s)
- Amy VandenBerg
- Clinical Pharmacy Specialist; Coordinator, Department of Pharmacy, Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, South Carolina,
| | - Jessica Broadway
- Assistant Professor, Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, South Carolina
| | - Callie Lalich
- Assistant Professor, Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, South Carolina
| | - Rachel Kennedy
- PGY3 Psychiatry Resident, Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, South Carolina
| | - Kristen Williams
- Assistant Professor, Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, South Carolina
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Doré M, San Juan AE, Frenette AJ, Williamson D. Clinical Importance of Monitoring Unbound Valproic Acid Concentration in Patients with Hypoalbuminemia. Pharmacotherapy 2017; 37:900-907. [DOI: 10.1002/phar.1965] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Maxime Doré
- Department of Pharmacy; Hôpital du Sacré-Coeur de Montréal; Montreal Québec Canada
| | | | - Anne Julie Frenette
- Department of Pharmacy; Hôpital du Sacré-Coeur de Montréal; Montreal Québec Canada
- Research Center; Hôpital du Sacré-Coeur de Montréal; Montreal Québec Canada
- Faculty of Pharmacy; University of Montreal; Montreal Québec Canada
| | - David Williamson
- Department of Pharmacy; Hôpital du Sacré-Coeur de Montréal; Montreal Québec Canada
- Research Center; Hôpital du Sacré-Coeur de Montréal; Montreal Québec Canada
- Faculty of Pharmacy; University of Montreal; Montreal Québec Canada
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Riker RR, Gagnon DJ, Hatton C, May T, Seder DB, Stokem K, Fraser GL. Valproate Protein Binding Is Highly Variable in ICU Patients and Not Predicted by Total Serum Concentrations: A Case Series and Literature Review. Pharmacotherapy 2017; 37:500-508. [PMID: 28173638 DOI: 10.1002/phar.1912] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
STUDY OBJECTIVE The free fraction of valproate (the pharmacologically active moiety, normally 5-10%) may vary significantly in critically ill patients, but this topic is understudied, with only four prior intensive care unit (ICU) case reports. The objective of this study was to evaluate the range of valproate plasma protein binding in ICU patients. DESIGN Observational study of consecutive ICU patients. SETTING Neurocritical and medical critical care services in a nonuniversity academic medical center. PATIENTS Consecutive ICU patients treated with valproate with serum albumin less than 4 g/dl. MEASUREMENTS AND MAIN RESULTS Simultaneous total and free trough serum valproate concentrations were measured as were serum creatinine, blood urea nitrogen, albumin, platelets, and transaminase values. The reference concentration range was 50-125 mg/L (total) and 5-17 mg/L (free). Valproate concentrations were categorized as within reference range, low, or high, and as concordant if both concentrations were in the same category. Data are reported as median (interquartile range). Fifteen patients (nine men) were evaluated. The median age was 63 (34-70) years. The valproate dose was 3 g/day (35 mg/kg/day). No patient had a valproate free fraction of 5-10%; the median was 48%, and the range was 15-89%. Total and free concentrations showed poor correlation (0.43) and were concordant in only two patients (both in the reference range). Free valproate concentration was poorly predicted by an equation correcting for albumin (r = 0.45). Suspected adverse drug events occurred in 10 patients: hyperammonemia in 7 of 12 tested (58%), elevated transaminases in 2 of 15 (13%), and thrombocytopenia in 5 of 15 (33%). CONCLUSIONS Protein binding of valproate was highly inconsistent in this cohort of ICU patients, and total valproate concentrations did not predict free concentrations, even when correcting for albumin. Additional research to define best practice for dosing and monitoring valproate and the relationship between free valproate concentrations and clinical or adverse effects in ICU patients is needed.
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Affiliation(s)
- Richard R Riker
- Critical Care Medicine, Maine Medical Center, Portland, Maine.,Neurocritical Care and Neuroscience Institute, Maine Medical Center, Portland, Maine
| | - David J Gagnon
- Department of Pharmacy, Maine Medical Center, Portland, Maine
| | - Colman Hatton
- Department of Emergency Medicine, University of Michigan School of Medicine, Ann Arbor, Michigan
| | - Teresa May
- Critical Care Medicine, Maine Medical Center, Portland, Maine.,Neurocritical Care and Neuroscience Institute, Maine Medical Center, Portland, Maine
| | - David B Seder
- Critical Care Medicine, Maine Medical Center, Portland, Maine.,Neurocritical Care and Neuroscience Institute, Maine Medical Center, Portland, Maine
| | - Katie Stokem
- Critical Care Medicine, Maine Medical Center, Portland, Maine.,Neurocritical Care and Neuroscience Institute, Maine Medical Center, Portland, Maine
| | - Gilles L Fraser
- Critical Care Medicine, Maine Medical Center, Portland, Maine.,Department of Pharmacy, Maine Medical Center, Portland, Maine
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Valproic acid-induced hyperammonemic encephalopathy in a full-term neonate: a brief review and case report. Eur J Clin Pharmacol 2017; 73:647-649. [PMID: 28168312 DOI: 10.1007/s00228-017-2208-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 01/19/2017] [Indexed: 10/20/2022]
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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.
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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
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Abstract
PURPOSE OF REVIEW Various antiepileptics, sedative and anesthetic agents are used in the neurocritical care setting and therapeutic drug monitoring (TDM) has been proposed as a means to individualize dosing to ensure efficacy, avoid toxicity, and to account for drug-drug interactions. The purpose of this review is to highlight key articles relating to TDM published in the last 5 years with a focus on drug therapy for seizures, status epilepticus, and traumatic brain injury. RECENT FINDINGS Current evidence supports TDM of first-generation antiepileptics, and free-level monitoring for phenytoin and valproic acid is recommended in the neurocritical care population. There are insufficient data to recommend routine TDM of second-generation antiepileptics at this time. In traumatic brain injury, routine TDM of barbiturate infusions appears to be of little value in guiding or evaluating patient response to therapy except to differentiate between drug-induced coma and brain death. Although TDM of sedative agents has been studied, the use of clinical sedation scales is preferred over TDM in evaluating a patient's level of sedation. SUMMARY Therapeutic drug monitoring plays an important role in the care of patients in the neurocritical care setting but is applicable only to a limited number of drugs.
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Lampon N, Tutor JC. Apparent clearance of valproic acid in elderly epileptic patients: estimation of the confounding effect of albumin concentration. Ups J Med Sci 2012; 117:41-6. [PMID: 22206465 PMCID: PMC3282241 DOI: 10.3109/03009734.2011.640412] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
BACKGROUND Valproic acid (VPA) apparent clearance (CL) estimated from total serum concentrations is analogous in elderly and non-elderly adult patients. As drug-protein binding decreases in old age, the aim of our study was to evaluate the confounding effect of the serum albumin concentration on the VPA apparent CL in elderly patients. METHODS In 102 epileptic out-patients treated with VPA in monotherapy, serum total steady-state trough concentrations (Css) were determined. Css concentrations were normalized for a 42 g/L albumin concentration (Css(N)), and the apparent CL and normalized apparent CL(N) were calculated. RESULTS A poor concordance of 53% was found in the classification of Css and Css(N) levels of VPA as subtherapeutic, therapeutic, or supratherapeutic dose. In the elderly (≥65 years) and non-elderly adult patients, the VPA apparent CL was similar; however, normalized apparent CL(N) was significantly lower in older patients (P < 0.01), with a 40% median decrease. CONCLUSIONS Total VPA concentrations should be interpreted with caution, mainly in older patients, in which determination of unbound or normalized total drug concentrations may be clinically useful. Normalization of total concentrations permits an estimation of the masking effect of serum albumin concentrations on the VPA apparent CL in elderly patients.
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Affiliation(s)
- Natalia Lampon
- Unidad Monitorización Fármacos, Laboratorio Central, Hospital Clínico Universitario, Instituto de Investigación Sanitaria (IDIS), 15706 Santiago de Compostela, Spain
| | - J. Carlos Tutor
- Unidad Monitorización Fármacos, Laboratorio Central, Hospital Clínico Universitario, Instituto de Investigación Sanitaria (IDIS), 15706 Santiago de Compostela, Spain
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Monitorización farmacocinética de antiepilépticos. FARMACIA HOSPITALARIA 2011; 35:326-39. [DOI: 10.1016/j.farma.2010.10.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Revised: 09/20/2010] [Accepted: 10/25/2010] [Indexed: 11/15/2022] Open
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Severe valproic acid intoxication: case study on the unbound fraction and the applicability of extracorporeal elimination. Eur J Emerg Med 2011; 16:330-2. [PMID: 19424075 DOI: 10.1097/mej.0b013e32832c7b18] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Among anticonvulsants, valproic acid (VPA) is cited as the most frequent cause of unintentional and intentional intoxications. Symptoms of VPA intoxication are diverse and are related to VPA plasma concentration. Although total plasma concentrations of less than 450 mg/l produce limited toxicity, severe intoxications (>850 mg/l) can induce coma and are ultimately life threatening. A 32-year-old comatose woman was admitted to the ICU at our hospital; she suffered from hypotension, respiratory depression, hypoglycaemia, sinus bradycardia, hyperammonaemia, metabolic acidosis, and her core body temperature was 33.7 degrees C. The total VPA plasma concentration was 1244 mg/l with an increased unbound fraction of 85%. After we administered multiple doses of activated charcoal, she underwent continuous veno-venous haemofiltration to reduce the plasma VPA concentration. As the total concentration decreased, the unbound fraction also decreased. Within 20 h of admission, the patient made a full recovery. In cases of VPA intoxication, protein-binding saturation and drug characteristics render extracorporeal elimination, an effective technique for eliminating the unbound drug. Its application should be considered, depending on clinical symptoms, VPA concentration (>300 mg/l), albumin concentration and ammonia concentration (>400 micromol/l). The application of this technique should be weighed against its risks. This case illustrates the clinical significance of applying continuous veno-venous haemofiltration in VPA intoxication because of protein-binding saturation, and suggests when extracorporeal elimination should be considered.
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Effect of valproic acid treatment on copper availability in adult epileptic patients. Clin Biochem 2010; 43:1074-8. [DOI: 10.1016/j.clinbiochem.2010.06.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2010] [Revised: 05/28/2010] [Accepted: 06/22/2010] [Indexed: 02/01/2023]
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Prescription patterns of psychotropic medications in elderly compared with younger participants who achieved a "recovered" status in the systematic treatment enhancement program for bipolar disorder. Am J Geriatr Psychiatry 2008; 16:922-33. [PMID: 18978253 PMCID: PMC2630050 DOI: 10.1097/jgp.0b013e318187135f] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES This study compares prescription patterns between young adults and elderly with bipolar disorder who achieved a recovery status during the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD). DESIGN STEP-BD is a multicenter National Institute of Mental Health-funded project designed to evaluate the longitudinal outcome of patients with bipolar disorder. The STEP-BD study involved extensive assessment across multiple domains including demographic data, diagnosis, symptom severity, treatment, and clinical status. Patients achieved "recovered" status when they experienced eight consecutive weeks without significant symptoms. PARTICIPANTS The authors analyzed data of all subjects who achieved a recovered status at least once in their participation. MEASUREMENTS The authors compared treatment regimes and doses among young participants with middle age (N = 3,364), 20-59 years old, and older participants 60 and above (N = 246). RESULTS Of the 3,615 STEP-BD participants who had a lifetime diagnosis of bipolar subtypes I or II, 67.6% (N = 2442) achieved a recovered status during their participation. A total of 78.5% (N = 193) of older patients recovered compared with 66.8% of the younger cohort. On average, participants who reached a recovered status took 2.05 medications with no difference between age groups. Lithium was prescribed to 37.8% of younger patients compared with only 29.5% of older participants. The mean dosages taken by younger and older patients differed significantly only for lithium, valproate, and risperidone with elderly individuals prescribed lower daily dosages. Significant reduction in lithium dosing was observed among individuals aged 50 and older and among individuals 60 and older for valproate. Although valproate was more often prescribed, 42.1% of recovered bipolar elder achieved recovery with lithium alone compared with only 21.3% of the younger cohort. CONCLUSION This data shows recovery is achievable in the elderly though more than one medication is often needed regardless of age.
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Ueshima S, Aiba T, Makita T, Nishihara S, Kitamura Y, Kurosaki Y, Kawasaki H, Sendo T, Ohtsuka Y, Gomita Y. Characterization of non-linear relationship between total and unbound serum concentrations of valproic acid in epileptic children. J Clin Pharm Ther 2008; 33:31-8. [PMID: 18211614 DOI: 10.1111/j.1365-2710.2008.00885.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To establish a regression equation to properly estimate the unbound serum concentration of valproic acid (VPA) from its total serum concentration; the relationship between total and unbound serum VPA concentrations was retrospectively characterized. METHODS Data were obtained from the clinical examination records that were routinely archived during therapeutic drug monitoring. The screening encompassed 342 records of 108 paediatric patients whose total and unbound VPA concentrations had been determined. The relationship between total and unbound VPA concentrations was characterized according to the Langmuir equation by taking account of inter-individual variability with the nonmem program. RESULTS The total VPA concentration (C(t)) in the screened patients ranged from 5.5 to 179.8 microg/mL, and the unbound VPA concentration (C(f)) increased in a non-linear manner as the total VPA concentration increased. Taking account of the effects of antiepileptics concurrently administered, the VPA dissociation constant (K(d)) and maximum binding site concentration (B(m)) were 7.8 +/- 0.7 and 130 +/- 4.5 microg/mL respectively, for the regression equation, C(t) = C(f) + B(m) x C(f)/(K(d) + C(f)). An alteration in the unbound concentration was seen in patients who were treated with the combination of VPA and ethosuximide and in those who received two additional antiepileptics. CONCLUSIONS A regression equation for estimation of the unbound VPA concentration, based on total VPA concentration collected during routine therapeutic drug monitoring was established. Use of two additional antiepileptics and ethosuximide treatment was considered as potential factors affecting unbound VPA concentration.
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Affiliation(s)
- S Ueshima
- Department of Hospital Pharmacy, Okayama University Hospital, Okayama, Japan
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