Safety range of free valproic acid serum concentration in adult patients

Risk factors for thrombocytopenia associated with intravenous valproic acid therapy in pediatric patients undergoing neurosurgical operations

Thrombocytopenia is one of the side effects of VPA. This study aimed to evaluate the incidence and risk factors of thrombocytopenia after intravenous VPA treatment in children with neurosurgical operations. Pediatric patients undergoing neurosurgical operations treated with intravenous VPA were enrolled in this retrospective study. According to platelet count after intravenous injection of VPA, the pediatric patients were divided into the thrombocytopenia group and the non-thrombocytopenia group. Binary logistic regression analysis was used to explore the risk factors for thrombocytopenia. A total of 252 children with neurosurgical operations were included in this study, and the incidence of thrombocytopenia was 12.3% (31/252). Univariate analysis showed that baseline platelet count, duration of VPA therapy, and blood loss were associated with the occurrence of thrombocytopenia after intravenous administration of VPA. Binary logistic regression revealed that baseline platelet count (OR 0.995, 95% CI 0.991-0.999) and blood loss (OR 0.995, 95% CI 0.991-0.999) were independent risk factors for thrombocytopenia after intravenous VPA in children undergoing neurosurgical operations. Our data show that thrombocytopenia is common in neurosurgical operations children treated with intravenous VPA, and that baseline platelet count is an independent risk factor for thrombocytopenia. Regular monitoring of baseline platelet count is important for whether to short-term prophylactic use intravenous VPA in children undergoing neurosurgical operations.

Antiepileptic drugs carbamazepine and valproic acid mediate transcriptional activation of CYP1A1 via aryl hydrocarbon receptor and regulation of estrogen metabolism

Cytochrome P450 1A1 (CYP1A1) actively catalyzes estrogen hydroxylation reactions and maintains the levels of neuroactive steroid estradiol. The widely prescribed first-line anti-epileptic drugs (AEDs) are considered to be a potent inducer of CYP1A1 and have also been observed to affect serum estradiol and calcium levels in patients with epilepsy. However, the ability of AEDs to interfere with CYP enzyme function and estrogen disposition is a relatively unexplored area. Here we investigate the effect of widely prescribed AEDs (carbamazepine and valproic acid) on CYP1A1 regulation and the levels of estradiol and calcium in cell supernatants of hepatocellular, HepG2, and neuronal, SH-SY5Y cells. We observed that both the AEDs significantly increased CYP1A1 expression and enzyme activity, which was accompanied by a decrease in estradiol and calcium levels in HepG2 cells. This induction of CYP1A1 mRNA and protein was fully prevented by aryl hydrocarbon receptor (AHR) knockdown and StemRegenin 1 (SR1) antagonism. Notably, the AEDs did not affect the AHR expression but regulated its nuclear translocation, potentially driving the transcriptional upregulation of CYP1A1. Furthermore, the knockdown of CYP1A1 in HepG2 cells elucidated a marked increase in estradiol and calcium levels. Later, this increase subsided upon AED exposure. Lastly, we observed a similar trend in estradiol and calcium alterations in SH-SY5Y cells on AED exposure, speculating the involvement of CYP1A1 induction via AEDs at neuronal sites. This work demonstrates that AEDs mediate the upregulation of CYP1A1 via an AHR-dependent mechanism and influence estrogen and calcium homeostasis.

Outpatient Management of Bipolar Disorder in Older Adults

PURPOSEOF REVIEW

Old age bipolar disorder (OABD), increasingly common as the population ages, presents unique diagnostic and treatment challenges. This selective review focuses on issues especially relevant to outpatient management.

RECENT FINDINGS

People with OABD may have similar frequency and severity of mood episodes compared to younger adults. Depression predominates, and mixed symptoms in both depressive and manic episodes are common. Comorbidity and excess mortality are high, with a particular bidirectional association with cerebrovascular disease. Lithium may outperform valproic acid and second-generation antipsychotics in efficacy. Tolerability and long-term safety can be improved with relatively lower target drug therapeutic levels. Outpatient clinicians treating OABD should take an active role in the recognition and management of medical comorbidities. A careful history and examination might reveal subtle signs of bipolar disorder or mixed features and change treatment. A primary target for treatment is to reduce polypharmacy when appropriate. Further trials are needed to make specific and clear recommendations in OABD.

Effect of patients in-use and accelerated stability conditions on quality attributes and pharmacokinetic profile of four FDA approved extended-release anti-epileptic-drug products

Divalproex (DVS) is a popular drug widely used in various neurological and psychiatric disorders. Commercially, it is a multisource-drug available in different generic equivalents. Incidents of (class II)-recalls have been repeated over the last years due to failure to consistently meet dissolution specifications. Class II recalls are known to be associated with temporary or medically reversible adverse health consequences. This study aimed to evaluate the dissolution profiles, among other quality attributes, of select FDA-approved extended-release DVS products before and after exposure to conditions usually seen as short-lived and insignificant on product stability, such as pharmacy dispensing and patients' in-use conditions to assess their possible role in the failures observed. Products were stored for 6 weeks in pharmacy vials at 30 °C/75 % RH to simulate patient in-use conditions, for 12 weeks in unsealed HPDE bottles at 25 °C/65 % RH to simulate the pharmacy storage conditions, and for 3 days in open containers at 40 °C/75 % RH for accelerated stability studies. Physicochemical changes were detected by near infrared imaging, Fourier transformed infrared, X-ray powder diffraction and differential scanning calorimetry. All samples were analyzed for in vitro dissolution. Two products were further selected for in vivo study on Beagle dogs before and after storage. The physicochemical characterization tests revealed changes in tablets' composition and drug crystallinity over time. An improved discriminatory dissolution test was developed and used in this study. The in vitro release testing revealed that short-lived environmental changes at 30 or 25 °C could fail some unit doses and significantly lower the drug release (average reduction among all products was 12.97 ± 11.3 % and 27.48 ± 10.26 %, respectively). Some extended-release products showed a significant increase in the amount of drug dissolved in the first 6 h (early burst) owing to changes in tablet surface morphology and enhanced drug dissolution. In vivo studies showed a decrease in the AUC0-t by overall average of 21.1 % using the non-transformed data, a decrease that mirrored the dissolution results. The study shows that significant changes can occur during routine drug dispensing and patients' use that might variably impact the stability and quality of commercial bioequivalent unit doses. It is possible that these changes may also contribute to the adverse effects reported on DVS or upon drug switches that were previously attributed to the intersubject variability. The study findings are encouraging to further investigate the effect of such minor excursions on the drug effectiveness during products' shelf lives especially for narrow therapeutic index drugs.

A Clinical Nomogram for Predicting Substandard Serum Valproic Acid Concentrations in Chinese Patients With Epilepsy

Background

It is well-known that substandard serum valproic acid (VPA) concentrations may lead to treatment failure of epilepsy. However, there is still a lack of a quick method to predict whether a patient's serum VPA concentration will reach the standard.

Objective

The aims of this study were to investigate the factors leading to substandard serum VPA concentrations in Chinese patients with epilepsy and develop a related nomogram for risk prediction.

Methods

From January 2019 to March 2022, a total of 1143 serum VPA concentrations were collected from 630 hospitalized Chinese patients with epilepsy who were monitored by the Department of Pharmacy of Lu'an People's Hospital, and complete clinical data were collected from the corresponding patients for retrospective analysis. All monitored serum VPA concentrations were further divided into a training cohort and a validation cohort. For the training cohort, serum VPA concentrations below 50 µg/mL and between 50 and 100 µg/mL were classified into the subtherapeutic group and therapeutic group, respectively. The variables were selected from the clinical data, and differences between the variables of the subtherapeutic and therapeutic groups were analyzed. The influencing factors leading to substandard serum VPA concentrations were screened via logistic regression analysis, and the screened influencing factors were used to establish the nomogram prediction model.

Results

Multivariate logistic regression analysis revealed that the daily dose per unit of body weight (mg/kg/d), route of administration, presence of hepatic lesions, hypoalbuminemia, and combination with carbapenems or barbiturates were independent factors influencing the occurrence of substandard serum VPA concentrations. On the basis of the results of the multivariate logistic regression analysis, a nomogram risk prediction model for substandard serum VPA concentration was established. The values of the C-index and internal verification results indicated that the nomogram model had good accuracy and discrimination. The decision curve revealed that the nomogram that predicted the risk of substandard serum VPA concentration had a greater net benefit value (ranging from 12% to 94%), indicating that the model had a wide prediction interval.

Conclusions

Our study established a nomogram risk prediction model for substandard serum VPA concentrations in Chinese patients with epilepsy, which can help doctors or patients control the serum VPA concentration within the target concentration range as soon as possible.

Effect of UGT1A6 and UGT2B7 polymorphisms on the valproic acid serum concentration and drug-induced liver injury

Aim: Valproic acid (VPA) is a classic broad-spectrum antiepileptic drug, with significant pharmacokinetic variability. Genetic polymorphisms contribute to this variability, influencing both VPA trough serum concentration (VPA concentration) and VPA-induced liver injury. Our study aims to investigate the association between polymorphisms of uridine diphosphate glucuronyl transferase (UGT) 1A6, UGT2B7 and VPA concentration and screen for potential genetic loci affecting VPA-induced liver injury.Methods: This study included epilepsy patients treated with VPA. PCR-RFLP method was used to determine the genotypes of UGT1A6 and UGT2B7. Chemiluminescent microparticle immunoassay was used to measure VPA concentration. Multiple linear regression and logistic regression were employed to analyze factors influencing VPA concentration and VPA-induced liver injury, respectively.Results: The correlation between UGT polymorphism and VPA concentration was analyzed in 133 samples. For VPA-induced liver injury, 105 patients were analyzed, with 29 in the liver injury group and 76 in the control group. Our finding showed patients with the UGT1A6-T19G variant had significantly lower VPA concentrations compared with wild-type patients and UGT1A6-T19G, A541G, A552C and UGT2B7-C802T, G211T, A268G polymorphisms showed no impact on VPA-induced liver injury.Conclusion: This study demonstrated UGT1A6-T19G polymorphisms affected the VPA concentration, providing a theoretical basis for the individualized clinical use of VPA.

Factors associated with subtherapeutic levels of valproic acid in hospitalized patients with epilepsy: A retrospective cohort study

Valproic acid (VPA) is a commonly used anti-seizure medication, owing to its efficacy and cost-effectiveness. However, maintaining appropriate serum levels is crucial due to the narrow therapeutic window, as subtherapeutic levels can lead to treatment failure or adverse outcomes. This study aimed to identify the factors associated with subtherapeutic serum levels of valproic acid in patients undergoing treatment. This retrospective cohort study was performed at a tertiary care hospital and involved inpatients aged ≥ 18 years who were receiving valproic acid for epilepsy treatment. Data were obtained through chart reviews and a Therapeutic Drug Monitoring database. Subtherapeutic VPA levels were defined as < 50 mg/L. Logistic regression was used to identify risk factors for subtherapeutic levels. Of the 152 patients, 96 (63.2%) had subtherapeutic VPA levels (<50 mg/L). Males were more likely than females to have subtherapeutic levels (OR 2.45, 95% CI: 1.15-5.22; P = .02). Previous use of phenytoin significantly increased the risk of subtherapeutic VPA levels (OR 2.58, 95% CI: 1.16-5.71; P = .02). VPA administration by syrup and doses below 15 mg/kg/day were associated with subtherapeutic levels (OR 3.28 and 2.34, respectively). Additionally, co-medications, such as topiramate and meropenem, also increased this risk (OR 5.09 and 4.64, respectively). This study identified several factors significantly associated with subtherapeutic levels of valproic acid, including males, prior phenytoin use, co-medications, such as topiramate and meropenem, and lower VPA dosages. These findings underscore the importance of careful monitoring and individualized treatment plans to maintain therapeutic VPA levels in clinical practice. Further research is needed to explore the clinical implications and to develop strategies to minimize the risk of subtherapeutic levels in patients receiving VPA.

Fixed parameters in the population pharmacokinetic modeling of valproic acid might not be suitable: external validation in Chinese adults with epilepsy or after neurosurgery

PURPOSE

This study aims to assess the predictive performance of published valproic acid (VPA) population pharmacokinetic (PPK) models using an external data set in Chinese adults with epilepsy or after neurosurgery.

METHODS

A total of 384 concentrations from 290 Chinese adults with epilepsy or after neurosurgery were used for external validation. Data on published VPA PPK models were extracted from the literature. Prediction-based diagnostics (such as F20 and F30), simulation-based diagnostics, and Bayesian forecasting were used to evaluate the predictability of models.

RESULTS

The results of prediction-based diagnostics of all models were unsatisfactory. Models B, F, and H showed the best prediction performance in simulation-based diagnostics and Bayesian forecasting, demonstrating superior precision and accuracy. Bayesian forecasting demonstrated significant improvements in the model predictability.

CONCLUSION

The published PPK models showed extensive variation in predictive performance for extrapolation among Chinese adults with epilepsy or after neurosurgery patients. Fixed parameters of Vd and Ka in the PPK modeling of VPA might be the reason for the unsatisfied predictive performance. Bayesian forecasting significantly improved model predictability and may help to individualize VPA dosing.

Joint use of population pharmacokinetics and machine learning for prediction of valproic acid plasma concentration in elderly epileptic patients

BACKGROUND

Valproic acid (VPA) is a commonly used broad-spectrum antiepileptic drug. For elderly epileptic patients, VPA plasma concentrations have a considerable variation. We aim to establish a prediction model via a combination of machine learning and population pharmacokinetics (PPK) for VPA plasma concentration.

METHODS

A retrospective study was performed incorporating 43 variables, including PPK parameters. Recursive Feature Elimination with Cross-Validation was used for feature selection. Multiple algorithms were employed for ensemble model, and the model was interpreted by Shapley Additive exPlanations.

RESULTS

The inclusion of PPK parameters significantly enhances the performance of individual algorithm model. The composition of categorical boosting, light gradient boosting machine, and random forest (7:2:1) with the highest R2 (0.74) was determined as the ensemble model. The model included 11 variables after feature selection, of which the predictive performance was comparable to the model that incorporated all variables.

CONCLUSIONS

Our model was specifically tailored for elderly epileptic patients, providing an efficient and cost-effective approach to predict VPA plasma concentration. The model combined classical PPK with machine learning, and underwent optimization through feature selection and algorithm integration. Our model can serve as a fundamental tool for clinicians in determining VPA plasma concentration and individualized dosing regimens accordingly.

Development and validation of an automatic machine learning model to predict abnormal increase of transaminase in valproic acid-treated epilepsy

Valproic acid (VPA) is a primary medication for epilepsy, yet its hepatotoxicity consistently raises concerns among individuals. This study aims to establish an automated machine learning (autoML) model for forecasting the risk of abnormal increase of transaminase levels while undergoing VPA therapy for 1995 epilepsy patients. The study employed the two-tailed T test, Chi-square test, and binary logistic regression analysis, selecting six clinical parameters, including age, stature, leukocyte count, Total Bilirubin, oral dosage of VPA, and VPA concentration. These variables were used to build a risk prediction model using "H2O" autoML platform, achieving the best performance (AUC training = 0.855, AUC test = 0.789) in the training and testing data set. The model also exhibited robust accuracy (AUC valid = 0.742) in an external validation set, underscoring its credibility in anticipating VPA-induced transaminase abnormalities. The significance of the six variables was elucidated through importance ranking, partial dependence, and the TreeSHAP algorithm. This novel model offers enhanced versatility and explicability, rendering it suitable for clinicians seeking to refine parameter adjustments and address imbalanced data sets, thereby bolstering classification precision. To summarize, the personalized prediction model for VPA-treated epilepsy, established with an autoML model, displayed commendable predictive capability, furnishing clinicians with valuable insights for fostering pharmacovigilance.

Total valproate versus free valproate in therapeutic drug monitoring for bipolar disorder: A cross-sectional study

INTRODUCTION

The debate about observing total versus free serum valproate levels for therapeutic drug monitoring (TDM) has been unresolved for decades. This study was planned to assess the agreement between the total versus free valproate levels and the advantage of one method over the other in TDM.

METHODS

The present cross-sectional study was done on 93 patients with bipolar disorder. The intraclass correlation coefficient, Bland Altman analysis, and Lin's concordance analysis were done to assess the agreement between the total and free valproate concentrations. Linear and polynomial models were constructed to evaluate the relation between the two measurements. Receiver operating characteristics analysis was done to compare the accuracy for differentiating remission from non-remission on Young's mania rating scale (YMRS).

RESULTS

The intraclass correlation coefficient and Lin's concordance correlation coefficient were 0.491 (p = .002) and 0.055 (95% CI:0.037, 0.073), respectively. Bland Altman's analysis showed proportional bias. A polynomial model of second order was found to be the best fit for the prediction of free valproate from the data for total valproate, and 81.4% of the variability in free valproate could be explained when adjusted for albumin levels. The area under the curve for total valproate was 0.60 when compared to free valproate 0.56 for differentiating between remission and non-remission, but the comparison between the two ROC analyses was not statistically significant.

CONCLUSION

Free valproate does not provide any added advantage over the total valproate levels; hence, total valproate levels may continue to be used as the marker for drug monitoring.

Evaluation of CYP2C19 Genetic Variant and Its Lack of Association with Valproic Acid Plasma Concentrations Among Zhuang and Han Schizophrenia Patients in Guangxi

Purpose

To investigate the CYP2C19 genotype distribution and allelic frequency among the Zhuang and Han schizophrenic populations in Guangxi, examine the correlation between CYP2C19 genetic variants and standardized blood levels of Valproic Acid (VPA) in schizophrenic patients, and evaluate the effects of age, gender, and Body Mass Index (BMI) on standardized VPA blood concentrations.

Patients and Methods

Between February and December 2022, 192 Zhuang and Han schizophrenia patients treated with VPA were studied. Steady-state VPA concentrations were determined using homogeneous enzyme immunoassays, and CYP2C19 *1, *2, and *3 loci via q-PCR. CYP2C19 genotype distributions between Zhuang and Han groups in Nanning were compared using chi-square tests and contrasted with other ethnicities. Non-parametric tests analyzed VPA variations, identifying critical factors through multivariate stepwise regression.

Results

The study identified five CYP2C19 genotypes at the *2 and *3 loci, with the *3/*3 genotype absent in both cohorts. The CYP2C19 distribution in Guangxi Zhuang and Han mirrors, yet diverges significantly from Hui and Kazakh groups. Among 192 subjects, VPA blood levels remained consistent across metabolic types and ages 18-60 but varied significantly by gender. Multivariate analysis revealed gender and BMI as significant factors, overshadowing CYP2C19 genotype and age.

Conclusion

In Guangxi, CYP2C19 genetic variants in Zhuang and Han schizophrenia patients demonstrate statistically indistinguishable allelic and metabolic distributions. Gender and BMI can influence standardized VPA blood concentrations in schizophrenia patients. However, in our study cohort, the CYP2C19 genotype and age are not the primary determinants of standardized VPA blood levels.

Chitosan Nanoparticles Loaded with Quercetin and Valproic Acid: A Novel Approach for Enhancing Antioxidant Activity against Oxidative Stress in the SH-SY5Y Human Neuroblastoma Cell Line

BACKGROUND

Multiple drug-delivery systems obtained by loading nanoparticles (NPs) with different drugs that have different physicochemical properties present a promising strategy to achieve synergistic effects between drugs or overcome undesired effects. This study aims to develop a new NP by loading quercetin (Que) and valproic acid (VPA) into chitosan. In this context, our study investigated the antioxidant activities of chitosan NPs loaded with single and dual drugs containing Que against oxidative stress.

METHOD

The synthesis of chitosan NPs loaded with a single (Que or VPA) and dual drug (Que and VPA), the characterization of the NPs, the conducting of in vitro antioxidant activity studies, and the analysis of the cytotoxicity and antioxidant activity of the NPs in human neuroblastoma SH-SY5Y cell lines were performed.

RESULT

The NP applications that protected cell viability to the greatest extent against H2O2-induced cell damage were, in order, 96 µg/mL of Que-loaded chitosan NP (77.30%, 48 h), 2 µg/mL of VPA-loaded chitosan NP (70.06%, 24 h), 96 µg/mL of blank chitosan NP (68.31%, 48 h), and 2 µg/mL of Que- and VPA-loaded chitosan NP (66.03%, 24 h).

CONCLUSION

Our study establishes a successful paradigm for developing drug-loaded NPs with a uniform and homogeneous distribution of drugs into NPs. Chitosan NPs loaded with both single and dual drugs possessing antioxidant activity were successfully developed. The capability of chitosan NPs developed at the nanometer scale to sustain cell viability in SH-SY5Y cell lines implies the potential of intranasal administration of chitosan NPs for future studies, offering protective effects in central nervous system diseases.

Revolutionizing Precision Medicine: Exploring Wearable Sensors for Therapeutic Drug Monitoring and Personalized Therapy

Precision medicine, particularly therapeutic drug monitoring (TDM), is essential for optimizing drug dosage and minimizing toxicity. However, current TDM methods have limitations, including the need for skilled operators, patient discomfort, and the inability to monitor dynamic drug level changes. In recent years, wearable sensors have emerged as a promising solution for drug monitoring. These sensors offer real-time and continuous measurement of drug concentrations in biofluids, enabling personalized medicine and reducing the risk of toxicity. This review provides an overview of drugs detectable by wearable sensors and explores biosensing technologies that can enable drug monitoring in the future. It presents a comparative analysis of multiple biosensing technologies and evaluates their strengths and limitations for integration into wearable detection systems. The promising capabilities of wearable sensors for real-time and continuous drug monitoring offer revolutionary advancements in diagnostic tools, supporting personalized medicine and optimal therapeutic effects. Wearable sensors are poised to become essential components of healthcare systems, catering to the diverse needs of patients and reducing healthcare costs.

A Rare Case of Valproic Acid Toxicity Requiring Hemodialysis

Valproic acid poisoning can have mild to fatal consequences depending on its body concentration. There are rare case reports and barely any known controlled studies on the use of hemodialysis as a last treatment resort. We report a rare valproic acid poisoning case at One Brooklyn Health/Interfaith campus, New York City, warranting intubation and hemodialysis. The patient is a 47-year-old male with a past medical history of seizure disorder, polysubstance use disorder, schizophrenia, and gastroesophageal reflux disease (GERD) who was brought to the medical emergency department (ED) for intentional valproic acid overdose with 60 tablets of his prescribed home Depakote DR 500 mg (~30 g). The patient's other outpatient medications included valproic acid, trazodone, acetaminophen, famotidine, fluoxetine, folic acid, hydrocortisone-aloe, multivitamin, nicotine polacrilex, and thiamine. The patient's initial blood tests showed high valproic acid, ammonia, ethanol, and lactate. About six hours after ED admission, the patient became somnolent, desaturated to 74% on a non-rebreather oxygen mask, warranting intubation and hemodialysis after noticing persistently high serum concentrations of valproic acid. The relatively low molecular weight (144 Daltons) and low volume of distribution of valproic acid suggest a potential benefit from hemodialysis, especially at a serum concentration of >850 mg/L or in the event of a shock. In this patient, mentation and stability status were improved after hemodialysis. Hemodialysis appears to be the last treatment resort for severe valproic acid poisoning.

Valproic Acid-Associated Hyperammonemia: A Systematic Review

BACKGROUND

Hyperammonemia is an adverse effect that poses clinical uncertainty around valproic acid (VPA) use. The prevalence of symptomatic and asymptomatic hyperammonemia and its relationship to VPA concentration is not well established. There is also no clear guidance regarding its management. This results in variability in the monitoring and treatment of VPA-induced hyperammonemia. To inform clinical practice, this systematic review aims to summarize evidence available around VPA-associated hyperammonemia and its prevalence, clinical outcomes, and management.

METHODS

An electronic search was performed through Ovid MEDLINE, Ovid Embase, Web of Science, and PsycINFO using search terms that identified hyperammonemia in patients receiving VPA. Two reviewers independently performed primary title and abstract screening with a third reviewer resolving conflicting screening results. This process was repeated during the full-text review process.

RESULTS

A total of 240 articles were included. Prevalence of asymptomatic hyperammonemia (5%-73%) was higher than symptomatic hyperammonemia (0.7%-22.2%) and occurred within the therapeutic range of VPA serum concentration. Various risk factors were identified, including concomitant medications, liver injury, and defects in carnitine metabolism. With VPA discontinued, most symptomatic patients returned to baseline mental status with normalized ammonia level. There was insufficient data to support routine monitoring of ammonia level for VPA-associated hyperammonemia.

CONCLUSIONS

Valproic acid-associated hyperammonemia is a common adverse effect that may occur within therapeutic range of VPA. Further studies are required to determine the benefit of routine ammonia level monitoring and to guide the management of VPA-associated hyperammonemia.

A novel method for predicting the unbound valproic acid concentration

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 (C_tVPA) and serum albumin (SA), (C_tVPA [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 C_tVPA values, the constructed formula showed a weak trend with C_tVPA or SA. The formula based on (C_tVPA [μM] - 2 × SA [μM]) had high prediction accuracy and wide applicability in predicting the unbound VPA concentration in patients without severe renal failure.

Valproic acid-induced hyperammonemia in neuropsychiatric disorders: a 2-year clinical survey

INTRODUCTION

Valproic acid (VPA)-induced hyperammonemia (HA) is a rare adverse effect reported even at therapeutic VPA levels. The present study aimed to investigate the characteristics of VPA-induced HA and its association with the total dose, duration, and level of VPA. This study also investigated whether the use of VPA in combination with other medications has any effect on elevating serum ammonia levels.

METHODS

A total of 316 patients with a history of VPA prescribed for underlying neuropsychiatric disorders were found eligible for the study. Data including demographic information, medical history and diagnosis, VPA dosage, VPA treatment duration, VPA level, and ammonia serum level were extracted and reviewed from our hospital records. The history of other neuropsychiatric medications was also included.

RESULTS

Among 316 patients receiving VPA, HA was observed in 54 (17%) patients, and 15 patients were symptomatic among them. There was no significant difference in demographics between symptomatic and asymptomatic HA groups except for the number of co-administrated medications (p = 0.044). Besides, VPA duration and dose did not show a significant difference between the two groups. Additionally, the VPA level was significantly higher in patients who used risperidone in addition to VPA (p = 0.019). Eventually, VPA level showed a significant association with ammonia level (p = 0.025) and symptomatic HA (p = 0.033) after adjusting for possible confounders.

CONCLUSION

VPA level showed a significant association with ammonia level and symptomatic HA. Moreover, co-administrated medications such as risperidone might have an impact on the serum level of VPA. Further studies are recommended to confirm these findings.

Comparative effectiveness of valproic acid in different serum concentrations for maintenance treatment of bipolar disorder: A retrospective cohort study using target trial emulation framework

BACKGROUND

There is a lack of consensus on the optimal serum valproic acid (VPA) concentration for maintenance therapy in bipolar disorder (BD). We aimed to investigate the association between serum VPA levels and risk of mood episode recurrence.

METHODS

We enrolled patients with BD from multiple medical institutions in Taiwan between January 1, 2001 and December 31, 2019. Patients were divided into three groups according to their serum VPA concentrations (< 50 μg/ml, 50-74 μg/ml, and 75-104 μg/ml). Adjusted hazard ratios (aHR) with 95% confidence intervals (CIs) compared times to mood episode recurrence using the < 50 μg/ml group as reference. A systematic review found relevant articles published before February 2022 (PROSPERO: CRD42022309661), and corresponding results were compared.

FINDINGS

This cohort included 896 patients for an intention-to-treat analysis. Compared with the < 50 μg/ml group, a non-significantly lower risk of mood episode recurrence was found in the 50-74 μg/ml (aHR, 95% CI: 0·86, 0·71-1·05) and 75-104 μg/ml (0·91, 0·71-1·18) groups. A per-protocol analysis of 481 patients found a significant risk reduction in the 50-74 μg/ml group (0·76, 0·60-0·97), with inconclusive results in the ≥ 75 μg/ml group (1·03, 0·73-1·46). A meta-analysis including two studies (254 patients) and our cohort found a similar significantly lower risk of mood episode recurrence in the 50-74 μg/ml group (HR, 95% CI: 0·83, 0·69-0·99), while risk reduction in the 75-99 μg/ml group (0·62, 0·26-1·48) did not differ significantly from that in the < 50 μg/ml group or the 50-74 μg/ml group.

INTERPRETATION

The combined results of this cohort and previous studies suggest that VPA between 50-74 μg/ml may be a more effective concentration to prevent acute mood episodes during maintenance therapy in patients with BD compared with VPA < 50 μg/ml.

FUNDING

Ministry of Science and Technology, Taiwan, and Chang Gung Medical Research Project.

Design of self-assembling anti-epileptic drug for long-acting drug delivery in vivo

Valproic acid (VPA) has been extensively used for the treatment of seizures in epilepsy. The recommended VPA concentration in the blood is in the range of 50-100 μg mL^-1 and its therapeutic efficiency is well recognized. Since its therapeutic range is relatively narrow, strict scheduling of daily self-medication is required to optimize therapeutic outcomes and avoid adverse effects. To facilitate patient convenience in long-term and chronic therapies, the development of a sustained drug delivery system for VPA is a promising strategy. In this study, an enzyme-metabolizable block copolymer possessing a valproate ester, poly(ethylene glycol)-b-poly(vinyl valproate), was synthesized. The synthesized block copolymers formed stable nanoparticles (denoted Nano^VPA) by self-assembly under physiological conditions and released VPA via enzymatic hydrolysis. Nano^VPA showed improved pharmacokinetics compared to sodium valproate in vivo, and therapeutic efficacy in a pentylenetetrazol (PTZ)-induced kindling mouse model after once-weekly administration.

Evaluation of Free Valproate Concentration in Critically Ill Patients

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.

Clinical Pharmacokinetic Monitoring of Free Valproic Acid Levels: A Systematic Review

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.

Therapeutic drug monitoring of phenytoin and valproic acid in critically ill patients at Windhoek Central Hospital, Namibia

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.

Predicting the occurrence of thrombocytopenia from free valproate levels: A prospective study

PURPOSE

The likelihood of valproate (VPA) induced thrombocytopenia increases with higher VPA levels. In critically ill patients, the biological active free VPA level cannot be predicted from the total serum level. In this study, we evaluated the relationship between trough free VPA serum levels and concomitant platelet counts and assessed risk factors for the development of thrombocytopenia with the aim of generating a formula specifying the probabilities of developing thrombocytopenia based on trough free serum VPA levels.

METHODS

Trough free VPA levels and concomitant platelet counts were collected from a large cohort of patients who participated in a prospective VPA monotherapy trial. Significant variables associated with thrombocytopenia in a univariate analysis were evaluated in a multivariate model. A receiver operator curve was performed to compute the trough free VPA levels with the greatest discriminating power in predicting thrombocytopenia.

RESULTS

844 trough free VPA levels and concomitant platelet counts obtained from 264 patients were analyzed. In a multivariate analysis, trough free VPA levels, gender, and baseline platelet counts were significantly associated with thrombocytopenia. Using stepwise regression and multivariate logistic regression analyses, we generated gender-specific formulas for predicting platelet counts and probabilities of developing thrombocytopenia. The trough free VPA with the greatest discriminating power to predict platelet values ≤ 100,000/μL was 16.65 µg/mL.

CONCLUSIONS

The generated model was based on trough free VPA levels and achieved high sensitivity and specificity. Our results are therefore generalizable and can be applied to estimate the probability of developing thrombocytopenia in critically ill patients.

CYP2C19 & UGT1A6 genetic polymorphisms and the impact on Valproic acid-induced weight gain in people with epilepsy: Prospective genetic association study

OBJECTIVES

To study the association between CYP2C19*2 (681 G > A) and UGT1A6*2 (552A > C) polymorphisms on Valproic acid (VPA)-induced weight gain in People with epilepsy (PWE).

METHODS

We recruited PWE on VPA monotherapy and genotyped for CYP2C19 and UGT1A6 polymorphisms. Association between CYP2C19 polymorphism and weight gain was the primary outcome parameter. We followed them up monthly for six months and recorded Body mass index (BMI), drug compliance, side effects, food frequency, physical activity.

RESULTS

Of 108 participants recruited, we assessed the association between the polymorphism and weight gain in 101 PWE for CYP2C19*2 and 103 PWE for UGT1A6*2 polymorphism. The proportion of participants with weight gain was higher in those with poor and intermediate metabolizer genotypes of CYP2C19 (*1/*2 and *2/*2) compared to extensive metabolizers (*1/*1) [53.3 % vs 31.7 %, RR 1.68, 95 % CI (1.01-2.79), P = 0.03]. However, CYP2C19*2 allele did not show an increased risk of weight gain over the CYP2C19*1 allele. No association could be demonstrated with UGT1A6 genotypes and weight gain. In logistic regression analysis, CYP2C19*2 carrier genotype was the independent predictor of weight gain. OR 2.89 [95% CI (1.07-7.84)]. There were no significant association with serum TSH, fT4, testosterone, and valproate levels with CYP2C19 or UGT1A6 polymorphisms.

SIGNIFICANCE

People with epilepsy carrying CYP2C19 polymorphisms (*1/*2) and (*2/*2) had 3 times higher risk of VPA-induced weight gain compared to wild type (*1/*1).

The Effect of Plasma Protein Binding on the Therapeutic Monitoring of Antiseizure Medications

Epilepsy is a widely diffused neurological disorder including a heterogeneous range of syndromes with different aetiology, severity and prognosis. Pharmacological treatments are based on the use, either in mono- or in polytherapy, of antiseizure medications (ASMs), which act at different synaptic levels, generally modifying the excitatory and/or inhibitory response through different action mechanisms. To reduce the risk of adverse effects and drug interactions, ASMs levels should be closely evaluated in biological fluids performing an appropriate Therapeutic Drug Monitoring (TDM). However, many decisions in TDM are based on the determination of the total drug concentration although measurement of the free fraction, which is not bound to plasma proteins, is becoming of ever-increasing importance since it correlates better with pharmacological and toxicological effects. Aim of this work has been to review methodological aspects concerning the evaluation of the free plasmatic fraction of some ASMs, focusing on the effect and the clinical significance that drug-protein binding has in the case of widely used drugs such as valproic acid, phenytoin, perampanel and carbamazepine. Although several validated methodologies are currently available which are effective in separating and quantifying the different forms of a drug, prospective validation studies are undoubtedly needed to better correlate, in real-world clinical contexts, pharmacokinetic monitoring to clinical outcomes.