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Brown CS, Liu J, Riker RR, Mara KC, Rabinstein AA, Fraser GL, May TL, Seder D, Gagnon DJ. Evaluation of Free Valproate Concentration in Critically Ill Patients. Crit Care Explor 2022; 4:e0746. [PMID: 37942235 PMCID: PMC10631734 DOI: 10.1097/cce.0000000000000746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Protein binding of valproate is variable in ICU patients, and the total valproate concentration does not predict the free valproate concentration, even when correcting for albumin. We sought to quantify valproate free concentration among ICU patients, identify risk factors associated with an increasing free valproate concentration, and evaluate the association between free valproate concentration with potential adverse drug effect. DESIGN Retrospective multicenter cohort study. SETTING Two academic medical centers. PATIENTS Patients greater than or equal to 18 years of age with concomitant free and total valproate concentrations collected in the ICU. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS Two-hundred fifty-six patients were included in the study, with a median age of 56 years (42-70) and 65% of patients were male. The median total valproate concentration was 53 µg/mL (38-70 µg/mL), the free valproate concentration was 12 µg/mL (7-20 µg/mL), and the free fraction was 23.6% (17.0-33.9%). Therapeutic discordance between the free and total valproate concentration occurred in 70% of patients. On multivariable analysis, increased free valproate concentration was associated with higher total valproate concentration (per 5 µg/mL increase, increase 1.72 µg/mL, 95% CI, 1.48-1.96) and lower serum albumin (per 1 g/dL decrease, increase 4.60 µg/mL, 95% CI, 2.71-6.49). There was no association between free valproate concentration and adverse effects. CONCLUSIONS The valproate total and free concentration was discordant in the majority of patients (70%). Increased valproate free concentration was associated with hypoalbuminemia and total valproate concentration. Clinical decisions based on total valproate concentration may be incorrect for many ICU patients. Prospective, controlled studies are needed to confirm these findings and their clinical relevance.
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Affiliation(s)
| | - JiTong Liu
- Department of Pharmacy, Beth Israel Deaconess Medical Center, Boston, MA
| | - Richard R Riker
- Department of Critical Care Services, Maine Medical Center, Portland, ME
- Tufts University School of Medicine, Boston, MA
| | - Kristin C Mara
- Department of Quantitative Health Sciences, Mayo Clinic, Rochester, MN
| | | | | | - Teresa L May
- Department of Critical Care Services, Maine Medical Center, Portland, ME
- Tufts University School of Medicine, Boston, MA
| | - David Seder
- Department of Critical Care Services, Maine Medical Center, Portland, ME
- Tufts University School of Medicine, Boston, MA
| | - David J Gagnon
- Tufts University School of Medicine, Boston, MA
- Department of Pharmacy, Maine Medical Center, Portland, ME
- Maine Medical Center Research Institute, Portland, ME
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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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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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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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