Plasma Valproate Research Articles

Retrospective Analysis of Steady-State Sodium Valproate Plasma Concentrations in Chinese Patients With Bipolar Disorder: Impact of Demographic and Clinical Characteristics.

This study comprehensively examined the demographic and clinical characteristics of patients undergoing valproic acid therapy and explored their potential impact on plasma valproic acid concentrations. All enrolled patients were administered the extended-release formulation. An in-depth investigation of factors, including dose, age, sex, body mass index, co-administered medications, and laboratory test findings, was conducted to evaluate their potential influence on study outcomes. In total, 164 patients met the inclusion criteria and were included in the analysis. The patient age ranged from 13 to 60 years, with a median age of 25.71 years. Most patients (89%) received a daily dose of 1 g valproic acid. Co-administered psychiatric medications included aripiprazole, quetiapine, and lorazepam. Laboratory test results, such as hemoglobin and transaminase levels, were also collected as part of the study. The average plasma valproic acid plasma concentration was 79.8 mg/L. The dose significantly affected valproic acid concentrations, as a higher percentage of measurements exceeded the therapeutic range at a daily dose of 1 g. Furthermore, females exhibited significantly higher valproic acid concentrations compared with males at the same dose ( P < 0.05). However, different age groups showed no statistically significant differences in valproic acid concentrations ( P > 0.05). The co-administered antipsychotic and antidepressant medications significantly affected valproate concentrations, as reflected in the multiple regression model ( P < 0.01). This study offers valuable insights into the demographic and clinical characteristics of patients undergoing valproic acid therapy. It highlights the influence of dose, sex, and concomitant medications on plasma valproic acid concentrations. Overall, these findings can help guide dose adjustments and implement personalized treatment strategies in valproic acid therapy.

Impact of CYP2C9*2 and *3 polymorphisms on valproate-associated adverse drug reactions in individualsliving with epilepsy: a case-control study.

Epilepsy is characterized by repeated seizure activity. Valproate, acommonly used antiepilepticdrug, shows large inter-individual variation in plasma valproic levels and causes many adverse drug reactions. Aim: To find the influence of CYP2C9*2 and *3 polymorphisms on valproate-associated adverse drug reactions and plasma valproic acid levelsin people with epilepsy. Methods: We recruited 158 peoplewith epilepsy(79 cases and 79 controls) from anepilepsy clinic. Steady-state plasma valproic acid levels were measured using liquid chromatography-mass spectrometryand genotyping of CYP2C9 variantswas carried out with helps of RT-PCR. Results: The presence of a mutantheterozygousgenotype showed an odds ratio (OR) of 2.82 (95% CI: 1.10-7.24) andthe adjusted OR was 5.39 (95% CI: 1.69-17.16). There was no significant difference in steady-state plasma valproate concentration between genotypes. Conclusion: The presence of amutant heterozygous CYP2C9 genotype possesses five-times the risk of developing adverse drug reactions to valproate in people with epilepsy.

Artificial Neural Network vs. Pharmacometric Model for Population Prediction of Plasma Concentration in Real-World Data: A Case Study on Valproic Acid.

We compared the predictive performance of an artificial neural network to traditional pharmacometric modeling for population prediction of plasma concentrations of valproate in real-world data. We included individuals aged 65years or older with epilepsy who redeemed their first prescription of valproate after the diagnosis of epilepsy and had at least one valproate plasma concentration measured. A long short-term memory neural network (LSTM) was developed using the training data set to fit the LSTM and the test data set to validate the model. Predictions from the LSTM were compared with those obtained from the population predictions from a pharmacometric model by Birnbaum et al. which had the best predictive performance for population predictions of valproate concentrations in Danish databases. We used the cutoff of ±20mg/L of prediction error to define good predictions. A total of 1,252 individuals were included in the study. The LSTM fitted using the training data set had poor predictive performance in the test data set, but better than that of the pharmacometric model. The proportion of individuals with at least one predicted concentration within ±20mg/L of observed concentration was largest in case of the LSTM (64.4%, 95% confidence interval (CI): 58.4-70.2%) compared with the pharmacometric model by Birnbaum et al. (49.8%, 95% CI: 47.0-52.6%). LSTM shows better predictive performance to predict valproate plasma concentrations compared with a traditional pharmacometric model in the investigated setting with real-world data in older patients with epilepsy where information on exact timepoints for both dosing and plasma concentration measurement are missing.

Impact of MDR1 and UGT Gene Polymorphisms on Sodium Valproate Plasma Concentration in Patients with Epilepsy.

This study aimed to identify the effects of multidrug resistance gene 1 (MDR1) and UGT gene polymorphisms on the plasma concentration of VPA in subjects with epilepsy and provide a reference for individualized medicine of patients with epilepsy. One hundred subjects with epilepsy who were treated with sustained release VPA monotherapy were enrolled. Sanger sequencing was used to detect the genotypes of MDR1_G1199A, MDR1_G2677T/A, UGT1A6_A 552C, T19G and UGT2B7_C161T. By adjusting the plasma concentrations of VPA with body weight and a total daily dose of VPA, the concentration-to-dose ratio of VPA (CDRV) was obtained. Data were analyzed using SPSS17.0. No mutation of MDR1_G1199A gene was detected. MDR1_G2677T/A site T allele frequency is 43.5%, A is 14%. The genetic frequencies of UGT1A6_A552C, T19G, and UGT2B7_C161T were 29.5%, 25.5%, and 36%, respectively. Significant differences in CDRV were observed between carriers of TT, TG, and GG genotypes in the UGT1A6_T19G polymorphism (p = 0.021, p < 0.05). The CDRV was significantly lower in patients carry UGT1A6_T19G GG genotype compared to TG ((3.40 ± 1.61) μg.kg/mL.mg) and TT ((4.33 ± 1.97) μg.kg/mL.mg) genotype. While the MDR1_G2677T/A, UGT1A6_A552C and UGT2B7_C161T gene polymorphisms had no effect on the plasma concentration of VPA (p > 0.05). The genetic polymorphisms of UGT1A6_T19G significantly affect the plasma concentration of VPA in patients with epilepsy and the mutation of this locus can decrease the blood concentration of VPA. The MDR1_G2677T/A, UGT1A6_A552C and UGT2B7_C161T gene polymorphisms did not affect the plasma VPA concentration in Han patients with epilepsy.

The effects of valproate on serum leptin, insulin, and lipid levels in epileptic children.

Weight gain is an important adverse effect of valproate (VPA) therapy. A number of mechanisms have been proposed for its pathophysiology. The aim of the present study is the evaluation of insulin, leptin and lipid levels in epileptic children on treatment with VPA. Thirty epileptic children treated with VPA, and 20 age-sex-matched healthy children, were enrolled in this study. Blood samples were taken and the body mass index was calculated for all of the subjects. Serum insulin, leptin, and lipid levels were compared between the two groups. Leptin levels were significantly higher in the patient group (P = 0.009) whereas body mass index values were comparable. There was a positive correlation between leptin and body mass index among both patient (r = 0.464, P = 0.01) and control groups (r = 0.734, P = 0.0001). Total cholesterol and low-density lipoprotein (LDL) cholesterol levels were lower in VPA-treated epileptic children than the control group (P = 0.008; P = 0.003, respectively). No significant difference was determined in insulin levels between the two groups. A negative correlation was observed between plasma VPA level and total cholesterol and LDL cholesterol levels in the patient group (r = -0.380, P = 0.03, r = -0.474, P = 0.008, respectively). This study demonstrated higher leptin levels in the patient group despite similar BMI values. Hence, it seems likely that VPA causes leptin resistance. Unlike other anti-epileptics, VPA does not produce an increase in serum cholesterol levels. On the contrary, lower levels of total and LDL cholesterol levels in VPA-receiving patients have been observed in our study.

Effects of atorvastatin and aspirin on post-stroke epilepsy and usage of levetiracetam.

Objective:Atorvastatin and aspirin have been used in treating different forms of epilepsy. However, their effect on post-stroke epilepsy (PSE) still needs to be validated by large-scale clinical studies. In addition, their impact on the use of the antiepileptic drug levetiracetam for post-stroke epilepsy remains to be explored. Thus, the aim of this study was to further evaluate the effect of atorvastatin and aspirin on PSE and their effect on the usage of the antiepileptic drug levetiracetam in PSE patients.Methods:Patients, aged 65 to 85 years, with newly diagnosed post-ischemic stroke epilepsy from August 30, 2014 to August 30, 2018 were included in the study, with the exclusion of those with coexisting conditions.Results:Initially, 1321 patients were included, and 780 remained in the study at the 1-year follow-up. During the study, atorvastatin treatment with or without aspirin reduced the number of clinical epileptic episodes in PSE patients. It also reduced the dosage of levetiracetam and achieved better control of epilepsy compared to levetiracetam mono-treatment. Aspirin co-treatment with levetiracetam did not result in a significant improvement. However, the combination of aspirin with atorvastatin significantly reduced the number of seizures compared to atorvastatin treatment alone.Conclusion:Atorvastatin and aspirin co-treatment with levetiracetam can reduce epilepsy in PSE patients and reduce the dosage of levetiracetam required for effective control of PSE.

Impact of CYP2C19 and CYP2C9 gene polymorphisms on sodium valproate plasma concentration in patients with epilepsy

BackgroundValproic acid (VPA) is a broad spectrum anticonvulsant drug, which could be partially metabolised by cytochrome P450 (CYP) 2C9 and 2C19 enzymes. This study was designed to investigate the relationship...

Altered plasma prostaglandin E2 levels in epilepsy and in response to antiepileptic drug monotherapy

Prostaglandin E2 (PGE2), a physiologically active lipid compound, is increased in several diseases characterized by chronic inflammation. To determine its significance in epilepsy-associated inflammation and response to antiepileptic drug (AED), we evaluated the plasma PGE2 (median, pg/ml) levels in drug-free patients with epilepsy (N = 34) and patients receiving AED monotherapy (N = 55) in addition to that in healthy controls (N = 34). When compared to controls, plasma PGE2 levels were significantly elevated in all drug-free patients independent of the type of epilepsy (137.2 versus 475.7 pg/ml, p < 0.0001). Among the patients receiving AED monotherapy, only valproate responders showed a significant decrease compared to both drug-free patients (232.1 versus 475.7 pg/ml, p < 0.01) as well as valproate non-responders (232.1 versus 611.9 pg/ml, p < 0.0001). Both responders and non-responders on phenytoin or carbamazepine monotherapy had elevated PGE2 levels similar to drug-free patients. In addition, no difference was observed in plasma profiles of PGE2 precursor, arachidonic acid among the groups. Our work presents the clinical evidence of the association between plasma PGE2 levels and valproate efficacy in patients with epilepsy.

Determination of unbound valproic acid in plasma using centrifugal ultrafiltration and gas chromatography:Application in TDM

AimIn order to monitor the free concentration of VPA in plasma, a simple and rapid method needs to be developed. MethodsThe 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. ResultsThe 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). ConclusionThis 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.

Gas chromatographic analysis of sodium valproate in plasma and urine after air assisted liquid-liquid microextraction

Gas chromatographic analysis of sodium valproate in plasma and urine after air assisted liquid-liquid microextraction

Valproate-Associated Parkinsonism: A Critical Review of the Literature.

Valproate was first approved as an antiepileptic drug in 1962 and has since also become established as a mood stabiliser and as prophylaxis for migraine. In 1979, Lautin published the first description of a valproate-associated extrapyramidal syndrome. Many cases of valproate-associated parkinsonism have subsequently been published, but uncertainties remain concerning its prevalence, risk factors and prognosis. The aim of this paper is to provide a critical review of the existing literature on valproate-associated parkinsonism and to discuss possible mechanisms. Literature databases were searched systematically: we identified a total of 116 patients with valproate-associated parkinsonism published in case reports, case series and systematic analyses. Prevalence rates ranged widely, between 1.4 and 75% of patients taking valproate. There was great heterogeneity with regard to clinical presentation, age of onset, valproate dose, concomitant conditions and imaging findings. In all patients apart from three, valproate plasma concentrations were within or even below the recommended reference range when the parkinsonism occurred. Parkinsonism was reversible in the majority of patients, although recovery was often prolonged and sometimes incomplete. A dopaminergic deficit was confirmed in three of six patients investigated with dopamine transporter imaging. Seven of 14 patients who were treated with dopaminergic medication had a good response. The quality of the evidence was assessed and probability of causation was examined using the Naranjo score, which ranged from 0 to 7 (median: 5.0). Several pathophysiological mechanisms, including altered gene expression and neurotransmitter signalling, enhanced neurodegeneration or unmasking subclinical dopaminergic degeneration, could theoretically lead to valproate-associated parkinsonism. Further studies are warranted to elucidate this entity and its underlying pathophysiology.

Valproate-Induced Liver Injury: Modulation by the Omega-3 Fatty Acid DHA Proposes a Novel Anticonvulsant Regimen

BackgroundThe polyunsaturated, ω-3 fatty acid, docosahexaenoic acid (DHA), claims diverse cytoprotective potentials, although via largely undefined triggers. Thus, we currently first tested the ability of DHA to ameliorate valproate (VPA)-evoked hepatotoxicity, to modulate its anticonvulsant effects, then sought the cellular and molecular basis of such actions. Lastly, we also verified whether DHA may kinetically alter plasma levels/clearance rate of VPA.Methods and ResultsVPA (500 mg/kg orally for 14 days in rats) evoked prominent hepatotoxicity that appeared as a marked rise (2- to 4-fold) in serum hepatic enzymes (γ-glutamyl transferase [γ-GT], alanine aminotransferase [ALT], and alkaline phosphatase [ALP]), increased hepatic lipid peroxide (LPO) and tumor necrosis factor-alpha (TNFα) levels, as well as myeloperoxidase (MPO) activity (3- to 5-fold), lowering of serum albumin (40 %), and depletion of liver reduced-glutathione (GSH, 35 %). Likewise, histopathologic examination revealed hepatocellular degeneration, replacement by inflammatory cells, focal pericentral necrosis, and micro/macrovesicular steatosis. Concurrent treatment with DHA (250 mg/kg) markedly blunted the elevated levels of liver enzymes, lipid peroxides, TNFα, and MPO activity, while raising serum albumin and hepatic GSH levels. DHA also alleviated most of the cytologic insults linked to VPA. Besides, in a pentylenetetrazole (PTZ) mouse convulsion model, DHA (250 mg/kg) markedly increased the latency in convulsion evoked by VPA, beyond their individual responses. Lastly, pharmacokinetic studies revealed that joint DHA administration did not alter serum VPA concentrations.ConclusionsDHA substantially ameliorated liver injury induced by VPA, while also markedly boosted its pharmacologic effects. DHA manipulated definite cellular machinery to curb liver oxidative stress and inflammation, without affecting VPA plasma levels. Collectively, these protective and synergy profiles for DHA propose a superior VPA-drug combination regimen.

Low-dose sodium valproate in the treatment of idiopathic generalized epilepsies

Most patients with idiopathic generalized epilepsies (IGEs) have good seizure control when on antiepileptic drugs. To analyze prospectively the response to low-dose sodium valproate (VPA) treatment (<1000 mg/day) together with plasma VPA levels in a cohort of patients with IGE. Patients with IGE were selected and followed for almost 2 years. In patients on VPA with no seizures in the last year, VPA dose was lowered to <1000 mg/day. Newly diagnosed patients with IGE started treatment on VPA directly on this low dose. Fifty-four patients were included, with juvenile myoclonic epilepsy (JME) in 23 (42.6%), juvenile absence epilepsy (JAE) in 17 (31.5%), and generalized tonic-clonic seizures only (GTCS only) in 14 (25.9%). VPA at low dose was administered to 38 (70%) patients. Mean plasma VPA level was 44.21 mg/l (18-78; SD 15.18). Seizure relapse during the 2-year follow-up was observed in 8 (21%). A reduction in adverse events was observed (P < 0.048). The only factor related to efficacy of VPA at low dose was syndromic diagnosis. Low-dose VPA controlled 92.9% (13) of patients with GTCS only, 78.3% (18) of those with JME, and 29.5% (5) of those with JAE. Low-dose VPA was a highly effective treatment for the majority of those with JME and GTCS only. The seizures in JAE tended to be more resistant to treatment, usually requiring higher doses of VPA or polytherapy.

Lacosamide in absence status epilepticus

the role of LCM in patients withidiopathic generalized epilepsy presenting with absence statusepilepticus (ASE) is currently unknown.A 57-year-old woman came to be under our observation afterexperiencing confusion and drowsiness, immediately afterwaking up. Her family history was unremarkable. Apart frommild mental retardation and epilepsy, she had no other medicalproblems. Raretonic-clonic seizures,andepisodesoflost contactlasting for a few seconds or minutes had occurredmonthly sincethe age of 6 yearsold despite havingbeen treatedwith 2000 mg/day valproate(VPA),300 mg/daylamotrigine(LTG),3000mg/daylevetiracetam (LEV), 300 mg/day topiramate, 100 mg/day phe-nobarbital. The interictal EEG showed generalized spike-waveand polyspike-wave discharges at 3–4 Hz, lasting from 1 to 3 s.Brain MRI and genetic analysis (karyotypeand array-CGH) werenormal. After 6 h from the onset of confusion, the patient wasadmitted to our centre and at that timeshe was on 2000mg/dayVPA (plasma VPA was 87 mg/L, range 50–100 mg/L) and3000 mg/day LEV (plasma LEV was 25 mg/L, range 10–37 mg/L). A long-term video-EEG monitoring was performed and ASEwas diagnosed. In particular, she was slow, vague, inattentive,with no verbal contact and displayed rare, small myoclonictwitches of the eyelids and facial muscles.The ictal EEG revealeda continuous, generalized, 2.5–4Hz spike, polispike-wavepattern and brief trains of polispikes during confusional state(Fig. 1a). Intravenous (IV) diazepam (10 mg in bolus) induced arapid but transient effect (Fig. 1b), with ASE reappearing after5 min. The administration of IVdiazepam (10 mg bolus) was alsorepeated withouteffect.Wethereforeadministeredan IVloadingdose of200mgLCMoveraperiodof15 min,througha peripheralline, diluted in 50 ml of normal saline. During and at the end ofinfusion, the clinical picture and EEG pattern were unchanged(Fig. 1c). After 10 min, an additional 200 mg of LCM wasadministered for 15 min without effect (Fig. 1d). No adverseeffects were observed during the administration of LCM and noECG andlaboratoryvalues-changesweredocumented.After24 hthe ASE spontaneously resolved. The patient was then given2000 mg/day VPA and 100 mg/day LTG, while LEV was graduallydiscontinued. She has now been seizure-free during the 12months of follow-up.Althoughthe most commonly used bolus dose of LCM is 200–400 mg over 3–5 min,

Acute renal failure caused by severe coagulopathy induced by the interaction between warfarin potassium and levofloxacin: a case report

To the Editor: A 30-year-old man took warfarin potassium (4 mg/day) for several years because of idiopathic dilated cardiomyopathy (ejection fraction was 48 %, and no arrhythmia was observed). His medical regimen included aspirin (100 mg/day), digoxin (0.25 mg/day), pimobendan (20 mg/day), and atenolol (50 mg/day); glimepiride (4 mg/day), voglibose (2.7 mg/day), and allopurinol (900 mg/day) (for diabetes mellitus and hyperuricemia); and milnacipran hydrochloride (25 mg/day), fluvoxamine maleate (200 mg/day), risperidone (2 mg/day), and sodium valproate (800 mg/day) (for Asperger’s syndrome). Despite the long-term use of these medicines, neither renal disorders nor bleeding tendencies were observed [prothrombin time (PT)-international normalized ratio (INR) (PT-INR) was controlled around 1.5]. The patient presented to the emergency room with hematuria. Laboratory analyses indicated elevated white blood cell counts (20,500 cells/m) and C-reactive protein levels (4.5 mg/dl), but no anemia. We suspected urinary tract infection; therefore, levofloxacin (900 mg/day) was prescribed. After 6 days, the patient was brought to the emergency room because of hypovolemic shock resulting from nasal hemorrhage (Hb 3.7 mg/dl, Hct 10.9 %). Prothrombin time (PT) could not be determined. Acute renal failure (ARF) was suspected because of elevated blood urea nitrogen (100 mg/dl), creatinine (6.2 mg/dl), and serum potassium (6.2 mmol/l) levels. Severe hematuria with a distinct blood clot was observed. Warfarin and aspirin were discontinued; vitamin K (20 mg) was administered. Under strict observation for volume overload, Ringer’s solution and washed red cells were administered. Sufficient spontaneous urine production was maintained. Renal function recovered without hemodialysis. The hypovolemic shock caused by nasal bleeding and severe hematuria resulted in prerenal ARF; the hematoma that obstructed the urinary tract resulted in postrenal ARF. We believed both preand postrenal ARF were present. The patient’s course of PTINR and creatinine values is shown in Fig. 1. The patient had been taking warfarin for 3 years. Bleeding improved with vitamin K; therefore, the cause of coagulopathy was thought to be reinforced by the effects of warfarin. Several drugs interact with warfarin [1]. We suspected that valproate, allopurinol, and levofloxacin could interact with warfarin. ARF may have caused elevated plasma valproate and allopurinol concentrations, which could have then interacted with warfarin. However, valproate and allopurinol previously had been taken routinely, without bleeding tendencies. Thus, the newly prescribed levofloxacin was mainly responsible for this coagulopathy. Ofloxacin suppress the propagation of vitamin K-producing enteric bacteria, and thus the effects of warfarin would be enhanced. Also, warfarin and ofloxacin competitively bind with protein. Thus, the free effect of warfarin increases with the use of ofloxacin [2]. Levofloxacin and ofloxacin are both C. Nemoto (&) Y. Ikegami J. Shimada Y. Tsukada Y. Abe C. Tase Department of Critical Care and Emergency Medicine, Fukushima Medical University, 1-Hikarigaoka, Fukushima 960-1295, Japan e-mail: nemo@fmu.ac.jp

Eicosapentaenoic acid ablates valproate-induced liver oxidative stress and cellular derangement without altering its clearance rate: Dynamic synergy and therapeutic utility

The omega-3 fatty acid eicosapentaenoic acid (EPA) is a superb nature's medicine, with still unfolding health benefits. Because hepatotoxicity is a prominent adverse drug reaction, we currently attempted a new approach in which EPA was challenged to both alleviate hepatotoxicity and provide synergy with anticonvulsant effects of valproate (VPA). Besides, we verified whether EPA may kinetically modulate the clearance rate of VPA. VPA (500mg/kg p.o., for 2weeks) caused rat hepatotoxicity that was manifested as notable (2- to 4-fold) rise in serum liver enzymes (GGT, ALT, and ALP), increased hepatic levels of lipid peroxides and TNF-α (3- and 7-fold) and activity of myeloperoxidase (MPO, 4-fold), lowering of serum albumin (42%), and depletion of liver reduced glutathione (GSH, 36%). Furthermore, histopathologic examination revealed hepatocellular degeneration, focal pericentral necrosis, infiltration of inflammatory cells, and steatosis. Joint treatment with EPA (300mg/kg) blunted the oxidative stress, TNF-α levels and MPO activity, while enhanced levels of serum albumin and hepatic GSH. EPA also ameliorated most of the hepatocellular anomalies evoked by VPA. Additionally, in a mouse PTZ convulsion model, EPA markedly augmented the anticonvulsant effects of VPA far beyond their single responses. On the other hand, pharmacokinetic analyses revealed that joint EPA administration had no effect on serum VPA concentrations. Collectively, results demonstrate for the first time that the ω-3 FA (EPA) markedly alleviated VPA-induced hepatotoxicity, oxidative stress, and inflammation, while enhanced its anticonvulsant effects without altering its clearance. Therapeutically, these protective and synergy profiles for EPA foster a more safe and efficacious drug combination regimen than VPA.

Pharmacokinetics of Valproic Acid in Guinea-pigs with Biliary Abnormality

To explore whether biliary cannulation, biliary obstruction or gall bladder obstruction could alter the disposition of valproic acid, guinea-pigs were subjected to common bile duct cannulation or ligation, gall bladder-neck ligation or sham surgery as a control. They were then given an intravenous (i.v.) dose of sodium valproate (50 mg kg-1) and the pharmacokinetics of valproic acid in each group were compared. In the cannulated group, significant decreases (P less than 0.05) in the area under the elimination curve (AUC), the volume of distribution at steady-state (Vdss) and the mean residence time (MRT) were observed. Significant increases (P less than 0.05) in the elimination rate constant (kz) and total clearance (CLtot) of valproic acid were noted. In the biliary obstructed guinea-pigs, the Vdss was significantly decreased (P less than 0.05). In the gall bladder obstructed guinea-pigs, there was a secondary peak of valproate plasma concentration, and the kz was significantly decreased. The biliary excretion of unchanged and conjugated valproic acid was 2.0 +/- 0.7 (s.e.m.) and 19.7 +/- 3.6 (s.e.m.)% of dose, respectively, and was almost completely reabsorbed in the enterohepatic recycling. Urinary excretion of unchanged and conjugated valproic acid, as well as non-conjugate metabolic clearance of valproic acid, were not significantly different among the four groups. The results suggest that the pharmacokinetics of valproic acid in guinea-pigs are particularly sensitive to interruption of the enterohepatic cycle. Biliary obstruction may elevate plasma concentrations owing to the decreased Vdss of valproic acid. Gall bladder obstruction may cause fluctuation of valproate plasma concentrations. The data indicate that the apparent total clearance of valproic acid is significantly less than the intrinsic clearance owing to enterohepatic recycling.

Fluctuating and constant valproate administration gives equivalent seizure control in rats with genetic and acquired epilepsy

Purpose Controlled-release formulations of Valproate (VPA) reduce side effects by minimizing peak plasma VPA concentrations in patients with epilepsy. However, the impact of this on anti-seizure efficacy has not been thoroughly explored. Here the pharmacokinetics and pharmacodynamics of chronic intermittent (consequently, peak VPA concentrations) and continuous VPA administration were directly compared in two rat models of epilepsy. Methods Genetic Absence Epilepsy Rats from Strasbourg (GAERS) received a single acute bolus of VPA (100 mg/kg intravenously) combined with electroencephalography (EEG) and/or blood sampling for 180 min post-injection. GAERS and epileptic rats post-kainic acid-induced status epilepticus were chronically infused intravenously (3–5 days, respectively) with (i) saline followed by in random order (ii) intermittent and (iii) continuous VPA (42 mg/kg/h), separated by two days of wash-out. Seizures were quantified using video-EEG monitoring and VPA levels measured in brain, cerebrospinal fluid and plasma. Results Following acute VPA administration seizure suppression in GAERS persisted after plasma VPA levels became very low. Chronic intermittent and continuous VPA significantly suppressed seizures in both models ( p < 0.01) with no difference between administration regimens. In GAERS, the pattern of seizure suppression during intermittent treatment was constant, in contrast to the fluctuating VPA plasma and brain levels. There was discordance between the temporal pattern of plasma, brain VPA levels and seizure suppression efficacy in GAERS. Conclusion Administration regimes that result in fluctuating VPA blood levels achieve equivalent sustained seizure suppression as those that maintain steady mid-range concentrations.

Concentration-dependent disposition of glucuronide metabolite of valproate.

The glucuronide conjugation metabolism of valproate (VPA) has been assessed to be non-linear within the therapeutic concentration range. However, disposition of its metabolite, valproic acid glucuronide (VPAG), in relation to VPA doses is unclear. The purpose of this study was to elucidate the characteristics of dose-related disposition of VPAG. Guinea-pigs were treated with an intravenous bolus dose of sodium valproate at 20, 100, 500 or 600 mg kg(-1). Plasma was sampled on a pre-selected time schedule, and bile and urine were collected. Concentrations of VPA and VPAG in plasma, bile and urine were determined by gas chromatography. The pharmacokinetics of VPA and VPAG both were dose-dependent. However, the plasma concentration-time profiles of VPAG and VPA were not parallel. At a usual dose of VPA (20 mg kg(-1)), plasma VPAG declined with plasma VPA, whereas at a high dose of VPA (>500mg kg(-1)), plasma VPAG was elevated against the decline of plasma VPA, which suggested accumulation of plasma VPAG possibly owing to saturated elimination. The biliary and urinary clearances of VPA (vCLb and vCLu) were independent of dose. However, the clearances of plasma VPA (vCLp), plasma VPAG (gCLp), biliary and urinary VPAG (gCLb and gCLu) all were decreased against the increase in VPA doses. The dose-dependent decrease of gCLu (from 3.19 to 1.12 mL min(-1)) was less pronounced than that of gCLp (from 6.72 to 0.86 mL min(-1)) and the gCLu turned to exceed the gCLp at high doses of VPA (> 500 mg kg(-1)). These results suggest that the excess urinary VPAG might be produced in kidney. In conclusion, at a high dose of VPA, plasma VPAG is accumulated. The concentration-dependent biliary and urinary recovery of VPAG might be governed by a saturable elimination process rather than by saturable hepatic biotransformation rate. Glucuronide conjugation metabolism of VPA in kidney is speculated, which might be minor at low levels of plasma VPA, but more obvious after saturation of hepatic glucuronidation.

Effects of Lithium on the Pharmacokinetics of Valproate in Rats

Combined treatment with lithium and valproate has been used for bipolar disorder. However, the studied interaction between these two drugs has not been fully investigated. We therefore examined the effects of lithium on the pharmacokinetics (plasma disappearance, metabolism and urinary excretion) of valproate in rats. Lithium (2 mEq kg(-1)) was administered intraperitoneally twice a day for ten days. Plasma disappearance curves of valproate (50 mg kg(-1), i.v.), valproate-metabolizing activities of UDP-glucuronosyltransferase (UGT) and cytochrome P450 (CYP) in liver microsomes and urinary excretion of free valproate and valproate-glucuronide were examined. The metabolizing activity of UGT and CYP were determined by enzyme assays and a fluorescence polarization immunoassay system. Urinary valproate-glucuronide was obtained using this system by subtracting the free level from total level, which was determined after deconjugating the sample with heat and NaOH. The half-life of plasma disappearance of valproate was 25% reduced by lithium pretreatment (0.428 +/- 0.031 h with repeated lithium pretreatment vs 0.578 +/- 0.062 h for controls). The valproate-metabolizing activity of UGT and CYP were not altered by lithium although lithium increased the urinary excretion of valproate-glucuronide. In conclusion, lithium pretreatment causes a decrease in plasma valproate levels and an increase in urinary excretion of valproate-glucuronide in rats.