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Mhaimeed N, Mhaimeed N, Shad MU. Pharmacokinetic mechanisms underlying clinical cases of valproic acid autoinduction: A review. JOURNAL OF AFFECTIVE DISORDERS REPORTS 2022. [DOI: 10.1016/j.jadr.2022.100426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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2
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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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Yang L, Lin IH, Ting CT, Tsai TH. Modulation of the transport of valproic acid through the blood-brain barrier in rats by the Gastrodia elata extracts. JOURNAL OF ETHNOPHARMACOLOGY 2021; 278:114276. [PMID: 34082013 DOI: 10.1016/j.jep.2021.114276] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 04/29/2021] [Accepted: 05/30/2021] [Indexed: 06/12/2023]
Abstract
HEADINGS ETHNOPHARMACOLOGICAL RELEVANCE Valproic acid (VPA) is primarily used as a medicine for the treatment of seizures. Gastrodia elata (G. elata) extract has been used as an alternative medicine for epilepsy patients. Cotreatment with VPA and G. elata extract is commonly prescribed in Taiwan and mainland China. Nevertheless, the mechanism of the blood-brain barrier (BBB) transportation effect of G. elata extract on VPA has not been characterized. AIM OF STUDY Our hypothesis is that G. elata extract modulates the BBB penetration of VPA through specific transporter transfer. MATERIALS AND METHODS A validated liquid chromatography-tandem mass spectrometry and multiple microdialysis method was developed to simultaneously monitor VPA in the blood and brain of rats. To investigate the mechanism of BBB modulation by the G. elata extract on VPA in the brain, cyclosporin A, a P-glycoprotein (P-gp) inhibitor and organic anion transporting polypeptide (OATP) inhibitor, was coadministered with the G. elata extract and VPA. RESULTS The pharmacokinetic results demonstrated that the VPA penetration ratio of the BBB, determined by the area under the concentration curve (AUC) ratio of VPA (AUCbrain/AUCblood), was approximately 0.36. After treatment with the G. elata extract (1 and 3 g/kg, p.o. for 5 consecutive days), the VPA penetration ratios were significantly enhanced to 1.47 and 1.02, respectively. However, in the experimental group coadministered cyclosporin A, the G. elata extract was unable to enhance the BBB transportation of VPA. Instead, the VPA penetration ratio in the brain was suppressed back to 0.38. CONCLUSIONS The present study reveals that the enhancement effect of the transporter mechanism of G. elata extract on VPA transport into the brain occurs through the OATP transporter but not the P-gp transporter.
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Affiliation(s)
- Ling Yang
- Institute of Traditional Medicine, School of Medicine, National Yang Ming Chiao Tung University, Taipei, 112, Taiwan
| | - I-Hsin Lin
- Institute of Traditional Medicine, School of Medicine, National Yang Ming Chiao Tung University, Taipei, 112, Taiwan
| | - Chin-Tsung Ting
- Division of Gastrointestinal Surgery, Department of Surgery, Ren-Ai Branch, Taipei City Hospital, Taipei, 106, Taiwan
| | - Tung-Hu Tsai
- Institute of Traditional Medicine, School of Medicine, National Yang Ming Chiao Tung University, Taipei, 112, Taiwan; Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, 804, Taiwan; School of Pharmacy, Kaohsiung Medical University, Kaohsiung, 807, Taiwan.
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Gu X, Zhu M, Sheng C, Yu S, Peng Q, Ma M, Hu Y, Li Z, Jiao Z, Zhou B. Population pharmacokinetics of unbound valproic acid in pediatric epilepsy patients in China: a protein binding model. Eur J Clin Pharmacol 2021; 77:999-1009. [PMID: 33423079 DOI: 10.1007/s00228-020-03080-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 12/28/2020] [Indexed: 11/28/2022]
Abstract
PURPOSE The purpose of this study was to establish a protein binding model of unbound valproic acid (VPA) based on Chinese pediatric patients with epilepsy and provide a reference for clinical medication. METHODS A total of 313 patients were included and both their total and unbound VPA concentrations (375 pairs of concentrations) were measured. NONMEM software was used for population pharmacokinetic modeling. The stepwise method was used to screen the potential covariates. Goodness-of-fit plot, bootstrap, and visual predictive check were used for model evaluation. In addition, dose recommendations for typical patients aged 0 to 16 years were proposed by Monte Carlo simulations. RESULTS A one-compartment model of first-order absorption and first-order elimination was used to describe the pharmacokinetic characteristics of unbound VPA, and the linear non-saturable binding equation was introduced to describe the protein binding. Body weight, age-based maturation, and co-medicated with lamotrigine could affect the CL/F of unbound and bound VPA. Model evaluation showed satisfactory robustness of the final model. The dosing regimens for children aged 0 to 16 years were proposed based on the final established model. CONCLUSION We developed a population pharmacokinetic model of unbound and bound VPA that took account of protein binding. The VPA dosing regimen in pediatric patients with epilepsy needs to be optimized by the body weight, age, and co-medications.
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Affiliation(s)
- Xurui Gu
- Department of Pharmacy, Xiangya Hospital, Central South University, No. 87, Xiangya Road, Changsha, 410008, Hunan Province, China
| | - Min Zhu
- Department of Pharmacy, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, 200030, China.,School of Basic Medicine and Clinical Pharmacy, China Pharmaceutical University, Nanjing, Jiangsu Province, 211198, China
| | - Changcheng Sheng
- Department of Pharmacy, Huashan Hospital, Fudan University, Shanghai, 200040, China.,Department of Pharmacy, Guizhou Provincial People's Hospital, Guiyang, 550002, Guizhou Province, China
| | - Shuran Yu
- Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, 410078, Hunan Province, China
| | - Qilin Peng
- Department of Pharmacy, Xiangya Hospital, Central South University, No. 87, Xiangya Road, Changsha, 410008, Hunan Province, China
| | - Mubai Ma
- Department of Pharmacy, Xiangya Hospital, Central South University, No. 87, Xiangya Road, Changsha, 410008, Hunan Province, China
| | - Yani Hu
- Department of Pharmacy, Xiangya Hospital, Central South University, No. 87, Xiangya Road, Changsha, 410008, Hunan Province, China
| | - Ziran Li
- Department of Pharmacy, Huashan Hospital, Fudan University, Shanghai, 200040, China
| | - Zheng Jiao
- Department of Pharmacy, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, 200030, China.
| | - Boting Zhou
- Department of Pharmacy, Xiangya Hospital, Central South University, No. 87, Xiangya Road, Changsha, 410008, Hunan Province, China.
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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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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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7
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Determination of unbound valproic acid in plasma using centrifugal ultrafiltration and gas chromatography:Application in TDM. Anal Biochem 2019; 588:113475. [PMID: 31634440 DOI: 10.1016/j.ab.2019.113475] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 09/27/2019] [Accepted: 10/11/2019] [Indexed: 11/24/2022]
Abstract
AIM In order to monitor the free concentration of VPA in plasma, a simple and rapid method needs to be developed. METHODS The free fraction of VPA in plasma was obtained by centrifugal ultrafiltration (CF-UF) devices. Cyclohexanecarboxylic acid was used as internal standard. Valproate in plasma was converted to VPA by sulphuric acid acidification, and dichloromethane was used as solvent for extraction. Nitrogen was the carrier gas, the samples were separated by capillary column, and the flame ionization detector was used to detect VPA fragment ions for quantitative analysis. RESULTS The assay had good specificity and stability. The linear range of the assay was 0.56-28.11 mg/L. The intra-day and inter-day precision (RSDs) of the assay were all within 15%, and the accuracy (RE) was 2.58%. The recoveries of VPA with three different concentrations were 102.03 ± 1.05, 101.45 ± 2.08 and 102.58 ± 3.38. The results of therapeutic drug monitoring (TDM) in pediatric inpatient group and outpatient group showed significant differences between the two groups (P < 0.001). CONCLUSION This assay has low cost and good analytical performance, so it can be developed into a routine TDM method of unbound VPA. We recommend the monitoring of unbound VPA concentration in pediatric inpatients during clinical use of VPA.
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Lam E, Bashir B, Chaballa M, Kraft WK. Drug interactions between direct-acting oral anticoagulants and calcineurin inhibitors during solid organ transplantation: considerations for therapy. Expert Rev Clin Pharmacol 2019; 12:781-790. [PMID: 31242782 DOI: 10.1080/17512433.2019.1637733] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Introduction: There is a high incidence of venous thromboembolism (VTE) in solid organ transplant recipients. The safety and efficacy of direct-acting oral anticoagulants (DOAC) have been well established in clinical practice for the prevention and treatment of VTE in broad populations. However, the management of VTE in the setting of solid organ transplantation remains a challenge to clinicians due to limited evidence of DOAC usage with calcineurin inhibitors. Areas covered: The current literature available on the pharmacokinetic-pharmacodynamic interaction between DOACs and calcineurin inhibitors is presented. A comprehensive review was undertaken using PubMed, Embase, drug product labeling, and drug product review conducted by the US Food and Drug Administration using Drugs@FDA. The potential for mitigation strategies and clinical management using extant knowledge is explored. Expert opinion: Immunosuppression therapy is necessary to prevent graft rejection by the host. The sparsity of data together with the lack of well-designed prospective studies of DOAC use in solid organ transplant recipients presents a unique challenge to clinicians in determining the clinical relevance of possible drug interactions. Existing evidence suggests that with attention to concomitant drug use and renal function, the co-administration of DOACs and calcineurin inhibitors is safe and effective.
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Affiliation(s)
- Edwin Lam
- a Department of Pharmacology & Experimental Therapeutics, Thomas Jefferson University , Philadelphia , PA , USA
| | - Babar Bashir
- b Department of Medical Oncology, Thomas Jefferson University Hospital , Philadelphia , PA , USA
| | - Mark Chaballa
- c Department of Pharmacy, Thomas Jefferson University Hospital , Philadelphia , PA , USA
| | - Walter K Kraft
- a Department of Pharmacology & Experimental Therapeutics, Thomas Jefferson University , Philadelphia , PA , USA
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McCudden CR. Quality, origins and limitations of common therapeutic drug reference intervals. ACTA ACUST UNITED AC 2018; 5:47-61. [PMID: 29794249 DOI: 10.1515/dx-2018-0001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 04/24/2018] [Indexed: 12/14/2022]
Abstract
Therapeutic drug monitoring (TDM) is used to manage drugs with a narrow window between effective and toxic concentrations. TDM involves measuring blood concentrations of drugs to ensure effective therapy, avoid toxicity and monitor compliance. Common drugs for which TDM is used include aminoglycosides for infections, anticonvulsants to treat seizures, immunosuppressants for transplant patients and cardiac glycosides to regulate cardiac output and heart rate. An essential element of TDM is the provision of accurate and clinically relevant reference intervals. Unlike most laboratory reference intervals, which are derived from a healthy population, TDM reference intervals need to relate to clinical outcomes in the form of efficacy and toxicity. This makes TDM inherently more difficult to develop as healthy individuals are not on therapy, so there is no "normal value". In addition, many of the aforementioned drugs are old and much of the information regarding reference intervals is based on small trials using methods that have changed. Furthermore, individuals have different pharmacokinetics and drug responses, particularly in the context of combined therapies, which exacerbates the challenge of universal TDM targets. This focused review examines the origins and limitations of existing TDM reference intervals for common drugs, providing targets where possible based on available guidelines.
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Affiliation(s)
- Christopher R McCudden
- Department of Pathology and Laboratory Medicine, Division of Biochemistry, University of Ottawa, 501 Smyth Rd., Ottawa, ON K1H 8L6, Canada
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10
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Determinants of free serum valproate concentration: A prospective study in patients on divalproex sodium monotherapy. Seizure 2018; 59:24-27. [DOI: 10.1016/j.seizure.2018.04.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 04/09/2018] [Accepted: 04/17/2018] [Indexed: 01/03/2023] Open
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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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12
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Monitoring Protein-Unbound Valproic Acid Serum Concentrations in Clinical Practice. Ther Drug Monit 2017; 39:269-272. [DOI: 10.1097/ftd.0000000000000405] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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13
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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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Wang Z, Yun Y, Xie X, You C, Miao H, Zhang F, Gao S, Chen W. Comparison of LC-MS/MS vs chemiluminescent microparticle immunoassay in measuring the valproic acid concentration in plasma of epilepsy patients in a new perspective. J Clin Lab Anal 2017; 32. [PMID: 28205314 DOI: 10.1002/jcla.22157] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 01/05/2017] [Indexed: 11/08/2022] Open
Abstract
OBJECTIVES This study was designed to compare the performance of LC-MS/MS with chemiluminescent microparticle immunoassay (CMIA) for determination of VPA in epilepsy patients in the perspective of metabolites' hepatotoxicity. METHOD Samples were collected and then analyzed using both LC-MS/MS and CMIA. A LO2 cells (normal human hepatic cells) experiment was carried out to confirm VPA metabolites' hepatotoxicity using AST(Aspertate Aminotransferase, AST), ALT(Alanine aminotransferase, ALT) and LDH(lactate dehydrogenase, LDH) in supernate as index. RESULTS The regression equation analysis showed as LC-MS/MS=1.0094CMIA-1.8937, with the concordance correlation coefficient of 0.9700, and the CUSUM test proved no significant deviation from linearity (P>.05). CMIA compared to LC-MS/MS gave a positive bias of 1.2 μg/mL. In LO2 experiment, VPA and its metabolites groups showed an obvious increment of AST, ALT, and LDH in supernate. CONCLUSION The LC-MS/MS is largely consistent with the CMIA in analytical time and quantification ability for VPA, but the LC-MS/MS can simultaneously determinate VPA and its metabolites in plasma, and is also a higher cost-efficiency method in consideration of toxic metabolites monitoring. The overestimation of VPA by CMIA showed no clinical significance. The metabolites 3-OH-VPA and 5-OH-VPA damage the LO2 cells and the results presented a statistical significance (P<.05). It is vital to monitor the metabolites' concentrations for VAP's clinical safety application, and now is the occasion that laboratory and clinic consider the LC-MS/MS method as a more advantageous alternative to CMIA method in therapeutic monitoring of VPA.
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Affiliation(s)
- Zhipeng Wang
- Department of Pharmacy, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Yunlei Yun
- Department of Pharmacy, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Xinfang Xie
- Department of Pharmacy, Changzheng Hospital, Second Military Medical University, Shanghai, China.,College of Chemistry and Bio-Engineering, Yichun University, Yichun, China
| | - Chunhua You
- Department of Pharmacy, Changzheng Hospital, Second Military Medical University, Shanghai, China.,College of Chemistry and Bio-Engineering, Yichun University, Yichun, China
| | - Haijun Miao
- Department of Pharmacy, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Feng Zhang
- Department of Pharmacy, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Shouhong Gao
- Department of Pharmacy, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Wansheng Chen
- Department of Pharmacy, Changzheng Hospital, Second Military Medical University, Shanghai, China
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15
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Gibbs HG, Zimmerman DE, Shermock KM, Clarke W, Mirski MA, Lewin JJ. Comparison of free fraction serum valproic acid concentrations between inpatients and outpatients. Am J Health Syst Pharm 2015; 72:121-6. [PMID: 25550135 DOI: 10.2146/ajhp140191] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
PURPOSE The differences in free fraction serum valproic acid concentrations between inpatients and outpatients were compared, and factors associated with therapeutic discordance were evaluated. METHODS This retrospective, single-center, cross-sectional study included patients with both a free and a total valproic acid concentration drawn within 30 minutes of each other between January 7, 2003, and June 1, 2011. Serum valproic acid concentrations were stratified by admission status (inpatient versus outpatient). In the primary analysis, for patients who had multiple paired concentrations drawn, one free valproic acid level and one total valproic acid level (i.e., one pair) were chosen at random for each inpatient. Information regarding patient demographics, laboratory data, and concomitant medication therapy was collected. Single and multivariable logistic regressions were performed to determine the odds of therapeutic discordance. RESULTS During the study period, inpatient concentrations were measured in 220 patients, and outpatient concentrations were measured in 41 patients. The median total valproic acid concentration in the inpatient group was significantly lower than that in the outpatient group (54 μg/mL versus 83 μg/mL, p < 0.001). The median free fraction of inpatient levels was nearly twice as high as that of outpatient levels (28.8% versus 15.5%, p < 0.001). Levels drawn in inpatients were therapeutically discordant 63% of the time compared to only 19% in outpatients (p < 0.001). Multivariable logistic regression identified low albumin as an independent risk factor for therapeutic discordance. CONCLUSION The median free fraction of valproic acid was significantly higher in inpatients than in outpatients. Low albumin concentration was a predictor of discordance between free and total valproic acid concentrations.
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Affiliation(s)
- Haley G Gibbs
- Haley G. Gibbs, Pharm. D., is Clinical Pharmacy Specialist, Department of Pharmacy, Johns Hopkins Hospital (JHH), Baltimore, MD. David E. Zimmerman, Pharm.D., is Assistant Professor of Pharmacy, Department of Clinical, Social, and Administrative Sciences, Mylan School of Pharmacy, Duquesne University, Pittsburgh, PA. Kenneth M. Shermock, Pharm.D., Ph. D., is Director of the Center for Medication Quality and Outcomes, Department of Pharmacy; William Clarke, Ph.D., is Associate Professor, Director of Clinical Toxicology, Department of Clinical Toxicology; Marek A. Mirski, M.D., Ph.D., is Vice-Chair and Director, Neuroscience Critical Care Unit, Department of Anesthesiology and Critical Care Medicine; and John J. Lewin III, Pharm.D., M.B.A., is Division Director, Critical Care and Surgery Pharmacy, Department of Pharmacy, and Adjunct Assistant Professor, Department of Anesthesiology and Critical Care Medicine, JHH.
| | - David E Zimmerman
- Haley G. Gibbs, Pharm. D., is Clinical Pharmacy Specialist, Department of Pharmacy, Johns Hopkins Hospital (JHH), Baltimore, MD. David E. Zimmerman, Pharm.D., is Assistant Professor of Pharmacy, Department of Clinical, Social, and Administrative Sciences, Mylan School of Pharmacy, Duquesne University, Pittsburgh, PA. Kenneth M. Shermock, Pharm.D., Ph. D., is Director of the Center for Medication Quality and Outcomes, Department of Pharmacy; William Clarke, Ph.D., is Associate Professor, Director of Clinical Toxicology, Department of Clinical Toxicology; Marek A. Mirski, M.D., Ph.D., is Vice-Chair and Director, Neuroscience Critical Care Unit, Department of Anesthesiology and Critical Care Medicine; and John J. Lewin III, Pharm.D., M.B.A., is Division Director, Critical Care and Surgery Pharmacy, Department of Pharmacy, and Adjunct Assistant Professor, Department of Anesthesiology and Critical Care Medicine, JHH
| | - Kenneth M Shermock
- Haley G. Gibbs, Pharm. D., is Clinical Pharmacy Specialist, Department of Pharmacy, Johns Hopkins Hospital (JHH), Baltimore, MD. David E. Zimmerman, Pharm.D., is Assistant Professor of Pharmacy, Department of Clinical, Social, and Administrative Sciences, Mylan School of Pharmacy, Duquesne University, Pittsburgh, PA. Kenneth M. Shermock, Pharm.D., Ph. D., is Director of the Center for Medication Quality and Outcomes, Department of Pharmacy; William Clarke, Ph.D., is Associate Professor, Director of Clinical Toxicology, Department of Clinical Toxicology; Marek A. Mirski, M.D., Ph.D., is Vice-Chair and Director, Neuroscience Critical Care Unit, Department of Anesthesiology and Critical Care Medicine; and John J. Lewin III, Pharm.D., M.B.A., is Division Director, Critical Care and Surgery Pharmacy, Department of Pharmacy, and Adjunct Assistant Professor, Department of Anesthesiology and Critical Care Medicine, JHH
| | - William Clarke
- Haley G. Gibbs, Pharm. D., is Clinical Pharmacy Specialist, Department of Pharmacy, Johns Hopkins Hospital (JHH), Baltimore, MD. David E. Zimmerman, Pharm.D., is Assistant Professor of Pharmacy, Department of Clinical, Social, and Administrative Sciences, Mylan School of Pharmacy, Duquesne University, Pittsburgh, PA. Kenneth M. Shermock, Pharm.D., Ph. D., is Director of the Center for Medication Quality and Outcomes, Department of Pharmacy; William Clarke, Ph.D., is Associate Professor, Director of Clinical Toxicology, Department of Clinical Toxicology; Marek A. Mirski, M.D., Ph.D., is Vice-Chair and Director, Neuroscience Critical Care Unit, Department of Anesthesiology and Critical Care Medicine; and John J. Lewin III, Pharm.D., M.B.A., is Division Director, Critical Care and Surgery Pharmacy, Department of Pharmacy, and Adjunct Assistant Professor, Department of Anesthesiology and Critical Care Medicine, JHH
| | - Marek A Mirski
- Haley G. Gibbs, Pharm. D., is Clinical Pharmacy Specialist, Department of Pharmacy, Johns Hopkins Hospital (JHH), Baltimore, MD. David E. Zimmerman, Pharm.D., is Assistant Professor of Pharmacy, Department of Clinical, Social, and Administrative Sciences, Mylan School of Pharmacy, Duquesne University, Pittsburgh, PA. Kenneth M. Shermock, Pharm.D., Ph. D., is Director of the Center for Medication Quality and Outcomes, Department of Pharmacy; William Clarke, Ph.D., is Associate Professor, Director of Clinical Toxicology, Department of Clinical Toxicology; Marek A. Mirski, M.D., Ph.D., is Vice-Chair and Director, Neuroscience Critical Care Unit, Department of Anesthesiology and Critical Care Medicine; and John J. Lewin III, Pharm.D., M.B.A., is Division Director, Critical Care and Surgery Pharmacy, Department of Pharmacy, and Adjunct Assistant Professor, Department of Anesthesiology and Critical Care Medicine, JHH
| | - John J Lewin
- Haley G. Gibbs, Pharm. D., is Clinical Pharmacy Specialist, Department of Pharmacy, Johns Hopkins Hospital (JHH), Baltimore, MD. David E. Zimmerman, Pharm.D., is Assistant Professor of Pharmacy, Department of Clinical, Social, and Administrative Sciences, Mylan School of Pharmacy, Duquesne University, Pittsburgh, PA. Kenneth M. Shermock, Pharm.D., Ph. D., is Director of the Center for Medication Quality and Outcomes, Department of Pharmacy; William Clarke, Ph.D., is Associate Professor, Director of Clinical Toxicology, Department of Clinical Toxicology; Marek A. Mirski, M.D., Ph.D., is Vice-Chair and Director, Neuroscience Critical Care Unit, Department of Anesthesiology and Critical Care Medicine; and John J. Lewin III, Pharm.D., M.B.A., is Division Director, Critical Care and Surgery Pharmacy, Department of Pharmacy, and Adjunct Assistant Professor, Department of Anesthesiology and Critical Care Medicine, JHH
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16
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Bohnert T, Gan LS. Plasma protein binding: from discovery to development. J Pharm Sci 2013; 102:2953-94. [PMID: 23798314 DOI: 10.1002/jps.23614] [Citation(s) in RCA: 233] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Revised: 04/25/2013] [Accepted: 04/25/2013] [Indexed: 12/25/2022]
Abstract
The importance of plasma protein binding (PPB) in modulating the effective drug concentration at pharmacological target sites has been the topic of significant discussion and debate amongst drug development groups over the past few decades. Free drug theory, which states that in absence of energy-dependent processes, after steady state equilibrium has been attained, free drug concentration in plasma is equal to free drug concentration at the pharmacologic target receptor(s) in tissues, has been used to explain pharmacokinetics/pharmacodynamics relationships in a large number of cases. Any sudden increase in free concentration of a drug could potentially cause toxicity and may need dose adjustment. Free drug concentration is also helpful to estimate the effective concentration of drugs that potentially can precipitate metabolism (or transporter)-related drug-drug interactions. Disease models are extensively validated in animals to progress a compound into development. Unbound drug concentration, and therefore PPB information across species is very informative in establishing safety margins and guiding selection of First in Human (FIH) dose and human efficacious dose. The scope of this review is to give an overview of reported role of PPB in several therapeutic areas, highlight cases where PPB changes are clinically relevant, and provide drug metabolism and pharmacokinetics recommendations in discovery and development settings.
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Affiliation(s)
- Tonika Bohnert
- Preclinical PK & In Vitro ADME, Biogen Idec Inc., Cambridge, Massachusetts 02142, USA.
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Fernández-Campos F, Calpena A, Soy D, Colom H. DETERMINATION OF TOTAL AND UNBOUND CONCENTRATIONS OF VALPROIC ACID IN HUMAN PLASMA BY LIQUID CHROMATOGRAPHY-TANDEM MASS SPECTROMETRY. J LIQ CHROMATOGR R T 2012. [DOI: 10.1080/10826076.2011.619027] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- F. Fernández-Campos
- a Biopharmaceutics and Pharmacokinetics Unit, Department of Pharmacy and Pharmaceutical Technology , School of Pharmacy, University of Barcelona , Barcelona , Spain
| | - A. Calpena
- a Biopharmaceutics and Pharmacokinetics Unit, Department of Pharmacy and Pharmaceutical Technology , School of Pharmacy, University of Barcelona , Barcelona , Spain
| | - D. Soy
- b Pharmacy Service, Hospital Clínic , Barcelona , Spain
| | - H. Colom
- a Biopharmaceutics and Pharmacokinetics Unit, Department of Pharmacy and Pharmaceutical Technology , School of Pharmacy, University of Barcelona , Barcelona , Spain
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18
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Salih MRM, Bahari MB, Abd AY. Selected pharmacokinetic issues of the use of antiepileptic drugs and parenteral nutrition in critically ill patients. Nutr J 2010; 9:71. [PMID: 21194458 PMCID: PMC3022641 DOI: 10.1186/1475-2891-9-71] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2010] [Accepted: 12/31/2010] [Indexed: 11/16/2022] Open
Abstract
OBJECTIVES To conduct a systematic review for the evidence supporting or disproving the reality of parenteral nutrition- antiepileptic drugs interaction, especially with respect to the plasma protein-binding of the drug. METHODS The articles related to the topic were identified through Medline and PubMed search (1968-Feburary 2010) for English language on the interaction between parenteral nutrition and antiepileptic drugs; the search terms used were anti-epileptic drugs, parenteral nutrition, and/or interaction, and/or in vitro. The search looked for prospective randomized and nonrandomized controlled studies; prospective nonrandomized uncontrolled studies; retrospective studies; case reports; and in vitro studies. Full text of the articles were then traced from the Universiti Sains Malaysia (USM) library subscribed databases, including Wiley-Blackwell Library, Cochrane Library, EBSCOHost, OVID, ScienceDirect, SAGE Premier, Scopus, SpringerLINK, and Wiley InterScience. The articles from journals not listed by USM library were traced through inter library loan. RESULTS There were interactions between parenteral nutrition and drugs, including antiepileptics. Several guidelines were designed for the management of illnesses such as traumatic brain injuries or cancer patients, involving the use of parenteral nutrition and antiepileptics. Moreover, many studies demonstrated the in vitro and in vivo parenteral nutrition -drugs interactions, especially with antiepileptics. CONCLUSIONS There was no evidence supporting the existence of parenteral nutrition-antiepileptic drugs interaction. The issue has not been studied in formal researches, but several case reports and anecdotes demonstrate this drug-nutrition interaction. However, alteration in the drug-free fraction result from parenteral nutrition-drug (i.e. antiepileptics) interactions may necessitate scrupulous reassessment of drug dosages in patients receiving these therapies. This reassessment may be particularly imperative in certain clinical situations characterized by hypoalbuminemia (e.g., burn patients).
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Affiliation(s)
- Muhannad RM Salih
- Department of Clinical Pharmacy, School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia
| | - Mohd Baidi Bahari
- Department of Clinical Pharmacy, School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia
| | - Arwa Y Abd
- Department of Clinical Pharmacy, School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia
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19
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Bentué-Ferrer D, Tribut O, Verdier MC. [Therapeutic drug monitoring of valproate]. Therapie 2010; 65:233-40. [PMID: 20699076 DOI: 10.2515/therapie/2010029] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2010] [Accepted: 03/11/2010] [Indexed: 11/20/2022]
Abstract
Valproic acid is an anticonvulsant drug available in France since 1967. It is a broad spectrum molecule indicated in various forms of epilepsy of the adult and the child, but it is also prescribed in the treatment of different other pathologies of nervous system. The divalproate sodium is indicated in the treatment of bipolar disorders. The valproic acid is marketed under various pharmaceutical forms, with different corresponding tmax values. But, whatever the administered preparation, the circulating active molecule is the ion valproate. Elimination half-life is from 11 to 20 h. Metabolization of valproate is important and represents its main route of elimination. Valpromide is comparable to a prodrug which metabolizes in valproate. The inter and intraindividual variability of the plasma concentrations are important. Several studies show a concentration-effect relationship, but two interventional trials ended in the lack of interest of the Therapeutic Drug Monitoring (TDM), although it is of current practice. However, numerous drug interactions may modify the plasma concentrations of valproate. The therapeutic range is from 50 to 100 mg/L (346-693 micromol/L). The level of proof of the interest of the TDM for this molecule was estimated in: recommended.
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20
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Dasgupta A. Usefulness of monitoring free (unbound) concentrations of therapeutic drugs in patient management. Clin Chim Acta 2007; 377:1-13. [PMID: 17026974 DOI: 10.1016/j.cca.2006.08.026] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2006] [Revised: 08/11/2006] [Accepted: 08/24/2006] [Indexed: 11/28/2022]
Abstract
Drugs are bound to various serum proteins in different degrees and only unbound or free drug is pharmacologically active. Although free drug concentration can be estimated from total concentration, for strongly bound drugs, prediction of free level is not always possible. Conditions like uremia, liver disease and hypoalbuminemia can lead to significant increases in free drug resulting in drug toxicity even if the concentration of total drug is within therapeutic range. Drug-drug interactions may also lead to a disproportionate increase in free drug concentrations. Elderly patients may have increased free drug concentrations due to hypoalbuminemia. Elevated free phenytoin concentrations have also been reported in patients with AIDS and pregnancy. Currently free drug concentrations of anticonvulsants such as phenytoin, carbamazepine and valproic acid are widely measured in clinical laboratories. Newer drugs such as mycophenolic acid mofetil and certain protease inhibitors are also considered as candidates for monitoring free drug concentration.
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Affiliation(s)
- Amitava Dasgupta
- Department of Pathology and Laboratory Medicine, University of Texas-Houston Medical School, 6431 Fannin, MSB 2.292, Houston, TX 77030, United States.
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21
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Hermida J, Tutor JC. A Theoretical Method for Normalizing Total Serum Valproic Acid Concentration in Hypoalbuminemic Patients. J Pharmacol Sci 2005; 97:489-93. [PMID: 15840952 DOI: 10.1254/jphs.fpe04007x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
In patients with hypoalbuminemia, the total serum concentration of valproic acid may offer poor clinical information; however, very few clinical laboratories routinely analyze the free concentration of the drug. The aim of this study was to design a procedure to normalize the total concentration of valproic acid according to the level of serum albumin and using previously published free fraction values. In 121 adult patients, with albumin levels of 18 - 41 g/L, the total concentration of valproic acid was normalized using the derived equation: C(N) = alpha(H)C(H)/6.5, where alpha(H) is the free fraction of the drug corresponding to the patient's particular albuminemia and C(H) is the total concentration of valproic acid. The value of 6.5 corresponds to the free fraction of the drug for a serum albumin of 42 g/L (percentile 50 of the reference range). For total concentrations lower than 75 mg/L, the predicted normalized valproic acid concentrations were reasonably concordant with the observed normalized concentrations calculated using the data from a protein-binding study. In a significant number of cases, subtherapeutic concentrations of the drug became therapeutic and even supratherapeutic when corrected according to the albumin levels. Furthermore, cases with therapeutic drug concentrations frequently became supratherapeutic when normalized. The limitations and clinical applications of the proposed formula for normalizing the total concentration of valproic acid are presented. It is concluded that it may be useful for the posological management of hypoalbuminemic patients when the free concentration of the drug is not available, and decisions have to be made based on the total serum concentration.
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Affiliation(s)
- Jesús Hermida
- Central Laboratory, University Hospital Clinic, Santiago de Compostela, Spain
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22
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Padilla López A, Ferriols Lisart R, Juan Aguilar M, Nicolás Picó J, Alós Almiñana M. Monitorización de la concentración libre de ácido valproico en un paciente posquirúrgico septicémico. FARMACIA HOSPITALARIA 2005; 29:215-6. [PMID: 16045433 DOI: 10.1016/s1130-6343(05)73665-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Sparreboom A, Chen H, Acharya MR, Senderowicz AM, Messmann RA, Kuwabara T, Venzon DJ, Murgo AJ, Headlee D, Sausville EA, Figg WD. Effects of α1-Acid Glycoprotein on the Clinical Pharmacokinetics of 7-Hydroxystaurosporine. Clin Cancer Res 2004; 10:6840-6. [PMID: 15501960 DOI: 10.1158/1078-0432.ccr-04-0805] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE UCN-01 (7-hydroxystaurosporine) is a small molecule cyclin-dependent kinase modulator currently under clinical development as an anticancer agent. In vitro studies have demonstrated that UCN-01 is strongly bound to the acute-phase reactant alpha (1)-acid glycoprotein (AAG). Here, we examined the role of protein binding as a determinant of the pharmacokinetic behavior of UCN-01 in patients. EXPERIMENTAL DESIGN Pharmacokinetic data were obtained from a group of 41 patients with cancer receiving UCN-01 as a 72-hour i.v. infusion (dose, 3.6 to 53 mg/m(2)/day). RESULTS Over the tested dose range, total drug clearance was distinctly nonlinear (P = 0.0076) and increased exponentially from 4.33 mL/hour (at 3.6 mg/m(2)/day) to 24.1 mL/hour (at 54 mg/m(2)/day). As individual values for AAG increased, values for clearance decreased in a linear fashion (R(2) = 0.264; P = 0.0008), although the relationship was shallow, and the data showed considerable scatter. Interestingly, no nonlinearity in the unbound concentration (P = 0.083) or fraction at the peak plasma concentration of UCN-01 was apparent (P = 0.744). CONCLUSION The results suggest the following: (1) that extensive binding to AAG may explain, in part, the unique pharmacokinetic profile of UCN-01 described previously with a small volume of distribution and slow systemic clearance, and (2) that measurement of total UCN-01 concentrations in plasma is a poor surrogate for that of the pharmacologically active fraction unbound drug.
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Affiliation(s)
- Alex Sparreboom
- Clinical Pharmacology Research Core, Division of Cancer Treatment and Diagnosis, National Cancer Institute, Bethesda, Maryland 20892, USA
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Abstract
Valproic acid and its derivatives are commonly administered antiepileptic drugs for children and adults. Five residents at a children's long-term care facility manifested hypoalbuminemia while being administered divalproex, although serum liver function test results and urinalysis results were normal. When the patients were free from valproic acid, the serum albumin levels increased into the normal range (17-30% higher than the serum albumin levels while patients were receiving valproic acid) despite the absence of any dietary changes. Comparing the serum albumin levels for eight residents who received divalproex (3.1 gm/dL +/- 0.4 gm/dL) with the serum albumin levels for 13 residents who were not receiving valproic acid or its derivatives (3.8 gm/dL +/- 0.2 gm/dL), the difference was significant (P < 0.001). This difference could not be accounted for by nutritional, environmental, laboratory, or urinary causes. In this study, divalproex administration was a contributing factor in the development of reversible hypoalbuminemia in this population of severely disabled, neurologically injured children and young adults. Further studies are required to determine the exact etiology and clinical significance of valproate-mediated hypoalbuminemia.
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Affiliation(s)
- Thomas A Rugino
- Children's Specialized Hospital, Toms River, New Jersey 08755, USA
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Abstract
Most drugs are bound to serum proteins to a various degree. Only unbound or free drug is pharmacologically active. Usually total drug is measured for therapeutic monitoring because there is equilibrium between bound and free drugs, and concentration of free drug can be predicted from total drug concentration. However, under certain conditions this equilibrium is disturbed and the measured free drug concentration can be significantly higher than expected from total drug concentrations, especially for strongly protein-bound drugs. In such case a patient may experience drug toxicity even if the total drug concentration is within the therapeutic range. Conditions like uremia, liver disease and hypoalbuminemia can lead to significant increases in free drug concentration. Therefore, monitoring free phenytoin and free valproic acid is recommended in these patients. Drug-drug interactions can also lead to a disproportionate increase in free drug concentration. One strongly protein-bound drug can significantly displace another strongly protein-bound drug if both drugs share the same binding site. Several over-the-counter pain medications such as salicylate, naproxen, and ibuprofen can cause significant displacement of both phenytoin and valproic acid from albumin binding site. Interestingly, such interactions are absent in uremic patients. Elderly patients may have increased free phenytoin or valproic acid due to hypoalbuminemia. Elevated free phenytoin concentrations have also been reported in patients with AIDS. Although digoxin is 25% bound to protein, monitoring free digoxin is useful in patients with elevated endogenous digoxin-like immunoreactive substances or in patients overdosed with digoxin and being treated with digibind. Monitoring free digoxin can also eliminate interference of Chinese medicines Chan Su and Danshen in serum digoxin measurement by certain immunoassays. However, free drug monitoring is not a routine procedure in clinical laboratories due to technical difficulties and lack of established reference ranges for free drugs.
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Affiliation(s)
- Amitava Dasgupta
- Department of Pathology and Laboratory Medicine, University of Texas-Houston Medical School, 77030, USA.
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