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PubMedDate not supplied

Comparative pharmacodynamics and brain distribution of E-delta 2-valproate and valproate in rats.

The E-isomer of 2-unsaturated valproate (E-delta 2-VPA) is a pharmacologically active metabolite of VPA that is less teratogenic and hepatotoxic than its saturated precursor. To assess potential use of E-delta 2-VPA as an alternate to VPA, a dose-response study comparing the anticonvulsant activity and neurotoxicity of E-delta 2-VPA and VPA was conducted in rats using the intravenous (i.v.) pentylenetetrazol (PTZ)-infusion threshold seizure model. Assay of drug in whole brain and plasma allowed comparison of the drug concentration-effect relationships and the brain distribution characteristics of the two compounds. E-delta 2-VPA was two to three times more potent than VPA in elevating the clonic seizure threshold of PTZ, in reference to either plasma or whole-brain drug concentrations. Furthermore, much steeper response curves were observed with E-delta 2-VPA as compared with VPA. Within the pharmacologic concentration range (defined as EC25 to EC75), E-delta 2-VPA was less neurotoxic than VPA as assessed by behavioral tests. Therefore, E-delta 2-VPA has a much more favorable protective index than VPA. At low doses, the concentration ratios of brain to plasma for both E-delta 2-VPA and VPA increased markedly with increasing plasma drug concentration. E-delta 2-VPA and VPA were previously shown to exhibit saturable binding to rat plasma proteins. If we assume that uptake of drug into the CNS is limited to the equilibrium plasma free fraction in the brain microvasculature, much of the nonlinear brain distribution features of VPA could be accounted for by saturable drug plasma protein binding. On the other hand, more complex kinetics involving simultaneous saturation of plasma protein binding and blood-to-brain transport are proposed to explain the brain distribution of the unsaturated compound. In addition, the brain-to-free drug concentration ratios for both E-delta 2-VPA and VPA were below unity at high drug-concentration range, consistent with the presence of an efficient efflux mechanism of these compounds from brain.

Animals↗
PubMedDate not supplied

Is 2-propyl-4-pentenoic acid, a hepatotoxic metabolite of valproate, responsible for valproate-induced hyperammonemia?

To investigate the association between valproate metabolism (VPA) and VPA-induced hyperammonemia together with the contribution of VPA hepatotoxicity risk factors such as young age, polypharmacy, and high serum VPA levels to VPA-induced hyperammonemia, plasma ammonia (NH3) levels, serum levels of VPA and its metabolites, and biochemical parameters were determined in 98 patients treated with VPA (53 monopharmacy cases and 45 polypharmacy cases). In monopharmacy patients, plasma NH3 levels did not depend on age, VPA dosage or serum levels. Serum level of 2-propyl-4-pentenoic acid (4-en) showed a negative correlation with plasma NH3 level in the monopharmacy group. In polypharmacy patients, plasma NH3 levels, serum glutamic pyruvic transaminase, and gamma-glutamyl-transpeptidase were significantly higher, while level/dose VPA ratio, 2-en-VPA serum level, and bilirubin were significantly lower than those in monopharmacy patients. These results suggest that young age and relatively high VPA serum levels within the therapeutic range were unlikely to be risk factors for common hyperammonemia associated with VPA therapy and that 4-en was not causally related to this adverse effect. The decreased serum level of 2-en-VPA in polypharmacy patients may be a reflection of a certain mitochondrial dysfunction, which might be a mechanism of the increased NH3 levels. The changes in biochemical parameters in polypharmacy patients were considered results of the enzyme-inducing activity of coadministered antiepileptic drugs (AEDs).

Adolescent↗
PubMedDate not supplied

Associations between risk factors for valproate hepatotoxicity and altered valproate metabolism.

The effects of three risk factors for valproate (VPA) hepatotoxicity (i.e., young age, polypharmacy, and high VPA serum level) on the metabolism of VPA to its monounsaturated metabolites [2-en-VPA (2-en), 3-en-VPA (3-en) and 4-en-VPA (4-en)] were investigated in 106 patients treated with VPA (56 cases of monotherapy and 50 cases of polytherapy). In the monotherapy group, there was a significant negative correlation between age and 4-en/VPA ratio. In the same group, the 4-en/VPA ratio showed a significant positive correlation with serum VPA level, while 3-en/VPA and 2-en/VPA ratios showed significant negative correlations. In patients greater than 10 years, the 4-en/VPA ratio was significantly higher, while the 2-en/VPA ratio was significantly lower in the polytherapy group than in the monotherapy group. Our results indicate that all three risk factors clearly increase the metabolic conversion of VPA to 4-en, the most toxic VPA metabolite, and that polytherapy and high VPA serum level result in the inhibited beta-oxidative metabolism of VPA to 2-en. These altered VPA metabolic profiles are strikingly similar to the abnormal VPA metabolism previously reported in cases with fatal hepatic failure. Although VPA-induced fatal hepatotoxicity has been regarded as an idiosyncratic reaction, it is possible that these three factors enhance susceptibility to VPA hepatotoxicity by altering the metabolism of VPA.

Age Factors↗
PubMed1996

Valproate metabolites in high-dose valproate plus phenytoin therapy.

PURPOSE: We wished to determine the relation between liver function, beta-, and omega-, and omega-1-oxidation metabolites and 4-en-valproate (VPA). METHODS: We measured the serum levels of VPA and its metabolites in children and adolescent receiving high-dose VPA plus phenytoin (PHT) therapy using gas chromatography-mass spectrometry with selected ion monitoring (GC/MS/ SIM). RESULTS: In high-dose VPA plus PHT polytherapy, the total VPA serum concentration was distinctly low, the concentrations of total beta-oxidation metabolites were decreased, the percentage values of VPA (percent of VPA) of total beta-oxidation metabolites were increased, and the E-2-en-VPA/3-keto-VPA ratios were decreased, as compared with those in high-dose VPA monotherapy. In high-dose VPA plus PHT polytherapy, 4-en-VPA (microM) was decreased and the concentrations of [omega + (omega-1)]-oxidation metabolites (microM) were decreased as compared with those in high-dose VPA monotherapy. In high-dose VPA plus PHT, serum glutamic-oxaloacetic transaminase (GOT), glutamic-pyruvic transaminase (GPT) and lactic dehydrogenase (LDH) did not correlate significantly with the ¿beta/omega + (omega-1)¿ metabolites ratio and 4-en-VPA levels, but serum GOT, GPT, and LDH were increased as compared with those in high-dose VPA therapy. We were not able to establish a significant relation between the formation of metabolites of VPA metabolites and liver dysfunction in patients receiving high-dose VPA and PHT concurrently. CONCLUSIONS: Metabolic levels do not appear to be a reliable predictor of hepatotoxicity in children receiving pharmacological antiepileptic drug (AED) therapy.

Adolescent↗
PubMed1998

Comparison of effects of valproate and trans-2-en-valproate on different forms of epileptiform activity in rat hippocampal and temporal cortex slices.

PURPOSE: Reducing the extracellular magnesium or calcium or increasing the extracellular potassium induces different patterns of epileptiform activity in the hippocampus and the entorhinal cortex. Although in the low Ca2+ and K+ models, seizure-like events (SLEs) develop in area CA1 of the hippocampus, only short recurrent discharges develop in the low Mg2+ model. In contrast, in low Mg2+, SLEs and late recurrent discharges (LRDs) are observed in the entorhinal cortex. METHODS: We compared the effects of valproate (VPA) and its major metabolite, trans-2-en-VPA (TVPA), on all these different model activities using extracellular field potential measurements. We also investigated the equilibration time course of VPA in the slice by using VPA-sensitive microelectrodes. RESULTS: Both drugs reversibly blocked most forms of epileptiform activity. The only exception was the LRDs in the entorhinal cortex. In paired experiments, TVPA appeared to be more effective than VPA bath applied with the same concentration to the same slice. With our measurements of the VPA concentrations in slices, we showed that the concentrations used were close to therapeutic drug levels. CONCLUSIONS: If TVPA stands the toxicological tests, it might be a useful alternative in the treatment of seizures.

Action Potentials↗
PubMed1999

Fatal liver failure associated with valproate therapy in a patient with Friedreich's disease: review of valproate hepatotoxicity in adults.

PURPOSE: Valproate (VPA)-associated hepatotoxicity is usually considered a problem of young children with polytherapy, mental retardation, and underlying metabolic defects. METHODS: An adult patient with fatal liver failure during treatment with VPA is presented, and a review of the literature on other adult patients is given. RESULTS: A 29-year-old female patient with Friedreich's ataxia and partial seizures with acute liver failure during VPA treatment is reported. The first symptoms of liver failure (i.e., apathy during febrile upper airway infection) occurred 2 months after starting VPA therapy. VPA was discontinued 10 days later on hospital admission, when she had hepatic encephalopathy and severe bleeding diathesis. The patient died of severe liver failure and bronchopneumonia after 4 weeks of supportive treatment. CONCLUSIONS: Twenty-six adult patients (>17 years) with VPA-associated fatal hepatotoxicity have been reported in the literature. Of the 26 adult patients, three were receiving VPA monotherapy. The age ranged between 17 and 62 years. The duration of VPA treatment before the first symptom varied between 7 days and 6 years. Twelve of the 26 affected adults had no underlying disease or a clearly nonmetabolic and non-hepatic disease. Therefore VPA-associated severe side effects also must be considered in adult patients without any evidence of a metabolic defect or underlying neurologic disease.

Adolescent↗
PubMed2001

Morphometric analysis of the cerebellar cortex capillaries in the course of experimental valproate encephalopathy and after chronic exposure to sodium valproate using transmission electron microscopy.

Morphometric analysis of the cerebellar cortex capillary cross-section area performed in experimental valproate encephalopathy using transmission electron microscopy showed that prolongation of VPA application resulted in more enhanced lumen narrowing manifested in gradual reduction in the mean value of the coefficient examined. After 6, 9 and 12 months of experiment this value was statistically different from that obtained in control subgroups, being respectively lower by approximately 22%, 48% and 65%. One month after terminating of chronic administration this value was close to the one found after 12 months of the study. Three months after the drug withdrawal the coefficient was higher by approximately 44% compared to the one after 12 months, which seemed to indicate an increase in capillary lumen patency. The morphometric analysis of the cerebellar cortex capillary cross-section area performed in the present study objectifies the results of qualitative ultrastructural investigations concerning the microcirculation of this CNS structure.

Animals↗
PubMed2004

Population pharmacokinetic model of valproate and prediction of valproate serum concentrations in children with epilepsy.

AIM: Using sparse data of valproate (VPA) serum concentrations to build a population pharmacokinetic (PPK) model of VPA in Chinese children with epilepsy and to predict serum concentrations for new patients using a Bayesian approach. METHODS: Two hundred epileptic children, whose VPA serum concentrations were collected, were divided randomly into two groups (A and B, n=100 each). The PPK parameter values of group A were calculated to establish a PPK Model by using the NPEM Program of USC*PACK software. Based on it, VPA serum concentrations of group B were predicted with the Bayesian Fitting Program of the USC*PACK software. To assess the accuracy and precision of prediction, a paired-comparisons t-test was run between predicted and observed concentrations, and then the mean prediction error (MPE), mean square prediction error (MSPE), root mean square prediction error (RMSPE), and coincidence rates for different percentages of prediction error were all calculated. RESULTS: Optimum PPK parameters were: Ka, 2.522+/-2.743 h(-1); Vs, 0.329+/-0.496 L/kg; and Kel, 0.0438+/-0.0384 h(-1). For group B, there was no significant difference between predicted and observed concentrations. MPE was -0.43 mg/L, MSPE was 115.40 (mg/L)2, and RMSPE was 5.47 mg/L. The coincidence rates for percentages of prediction error, which were less than 5 %, 10 %, 15 %, 20 %, 25 %, and 30 %, were 62 %, 74 %, 82 %, 85 %, 89 %, and 93 %, respectively. CONCLUSION: A PPK model of VPA in epileptic children was successfully established. Based on it, VPA serum concentrations can be predicted accurately with a Bayesian approach.

Adolescent↗
PubMed2004

Valproate-induced alterations in human theca cell gene expression: clues to the association between valproate use and metabolic side effects.

Valproic acid (VPA) is an anti-epileptic drug that has been associated with polycystic ovary syndrome (PCOS)-like symptoms, including increased ovarian androgen production. The hyperandrogenemia likely reflects the stimulatory action of VPA on theca cell androgen synthesis and has been correlated to its activity as a histone deacteylase inhibitor in these cells. To determine whether VPA induces a PCOS-like genomic phenotype, we compared the gene expression profiles of untreated (UNT) normal, VPA-treated normal, and UNT PCOS theca cells. Hierarchal cluster analysis demonstrated similarities in the gene expression profiles of VPA-treated normal and PCOS theca cells. Statistical analysis identified 1,050 transcripts that have significantly altered mRNA abundance in both VPA-treated normal and UNT PCOS theca cells compared with normal UNT theca cells. Among these 1,050 transcripts were cAMP-GEFII and TRB3, which have increased and decreased mRNA abundance, respectively. The altered abundance of these two mRNAs was correlated to increased basal and insulin-induced phosphorylation of protein kinase B (Akt/PKB). Thus these studies indicate that VPA- and PCOS-induced changes in gene expression enhance Akt/PKB signal transduction in human theca cells. Furthermore, common changes in gene expression in PCOS and VPA-treated normal theca cells suggest a possible mechanism for the development of PCOS-like symptoms, including increased steroid synthesis and arrested follicle development in women receiving chronic VPA therapy.

Anticonvulsants↗
PubMed2002

Valproate and valproate-analogues: potent tools to fight against cancer.

The branched-chain fatty acid valproic acid (VPA) is the most commonly used antiepileptic drug for treating generalized epilepsy. Although originally considered to be of low toxicity, VPA has proved to possess considerable teratogenic potential when applied to the pregnant epileptic women. During the last few years, it has become evident that some of the mechanisms which account for the malformations produced by VPA are related to distinct anti-tumor properties of this compound. This intriguing discovery opens novel aspects for the treatment of tumor patients. In the present review, the biological, biochemical and pharmacological properties of VPA are discussed. Analyses of structure-activity relationships can provide the necessary insight into the molecular structures responsible for the anti-tumor effects.

Animals↗
PubMed1996

A comparison of the effects of valproate and its major active metabolite E-2-en-valproate on single unit activity of substantia nigra pars reticulata neurons in rats.

Numerous findings suggest that the substantia nigra pars reticulata (SNR) acts as a seizure-gating mechanism and constitutes a site where protection against a broad spectrum of seizures can be obtained by inhibiting the activity of GABAergic output neurons to SNR target regions, particularly the superior colliculus. Most pharmacological studies on SNR neurons have been conducted with local microinjection of drugs, whereas studies with systemic administration of anticonvulsant drugs, e.g., the antiepileptic drug valproic acid (VPA), have yielded inconsistent data. In the present study, we examined the dose response and time course of the effects of anticonvulsant doses of VPA and its major active metabolite E-2-en-VPA on extracellularly recorded spontaneous single unit activity of nondopaminergic SNR neurons in a large group of chloral hydrate-anesthetized rats. The activity of each neuron was recorded over a period of at least 30 min after intravenous drug or vehicle administration. Both drugs rapidly decreased the firing rate of SNR neurons. Compared with predrug base-line values of neuronal firing of SNR neurons, the average peak inhibition of neuronal activity was approximately 16% at the lowest dose (50 mg/kg), approximately 20% (VPA) or 30% (E-2-en-VPA) at 100 mg/kg and approximately 50% (VPA) or 60% (E-2-en-VPA) at the highest dose (200 mg/kg) tested. ED50 values calculated from these data were 240 mg/kg for VPA and 159 mg/kg for E-2-en-VPA, respectively. Determination of drug levels in SN at time of peak effect after administration of 100 mg/kg VPA or E-2-en-VPA indicated that E-2-en-VPA exhibited its inhibitory effect on SNR firing at significantly lower concentration than VPA, suggesting that E-2-en-VPA is more potent than VPA in this regard. Except one SNR neuron, all neurons recorded in 52 rats reacted with a reduction in firing rate to administration of VPA or E-2-en-VPA, demonstrating a rather homogeneous susceptibility of SNR neurons to these drugs. The inhibition of SNR neurons by these drugs could be a result of increased GABA turnover, which has previously been reported to be induced in this region by systemic administration of VPA. We conclude that the ability of VPA and E-2-en-VPA to reduce firing of SNR neurons could be critically involved in their effectiveness in inhibiting seizures in various experimental models.

Animals↗
PubMed2003

Valproate for acute mood episodes in bipolar disorder.

BACKGROUND: Bipolar disorder is a common debilitating illness, characterised by acute affective episodes with full or partial inter-episode remission. Effective and acceptable treatment of acute episodes is required. Valproate has become a leading adjunctive and alternative mood stabilising treatment to lithium in bipolar disorder. OBJECTIVES: To determine the efficacy and acceptability of valproate in the treatment of acute episodes of bipolar disorder. SEARCH STRATEGY: The search included the Cochrane Collaboration Depression, Anxiety and Neurosis Controlled Trials Registrar (CCDANCTR), the Cochrane Controlled Clinical Trials Register (CCTR), reference lists of relevant papers and books, and contact with authors of trials, experts and pharmaceutical companies. SELECTION CRITERIA: Randomised controlled trials comparing valproate with placebo, other mood stabilisers and antipsychotic medication in the treatment of any bipolar affective episode. Participants were of both sexes, of all ages, with a diagnosis of bipolar affective disorder approximating to ICD 10 Code F31 and DSM IV 296. DATA COLLECTION AND ANALYSIS: Methodological quality was assessed independently by two reviewers blind to the authorship and source of papers. Ten randomised controlled trials were found comparing valproate with other interventions in mania. None was found examining its use in depression or mixed affective episodes. Data were extracted on the main outcome 'failure to respond by the end of the study' assessed by a less than 50% reduction in the Young Mania Rating Scale or the SADS-S mania scale. Three trials (316 participants) compared valproate with placebo. Three trials (158 participants) compared valproate with lithium. Two trials (363 participants) compared valproate with olanzapine. One trial (36 participants) compared valproate with haloperidol. Two trials (59 patients) compared valproate with carbamazepine. Acceptability of treatment was estimated using the outcome measure 'total number of subjects withdrawing from the study'. Three trials (321 patients) contributed to the comparison between valproate and placebo, two studies (144 patients) contributed to the comparison with lithium. One study (30 patients) provided data on this outcome in the comparison between valproate and carbamazepine. Pooled relative risks (with 95% confidence intervals) were calculated using fixed effect approaches. MAIN RESULTS: Valproate was more efficacious than placebo (RRR 38%; RR 0.62; 95% C.I. 0.51 to 0.77) in the treatment of mania. There was no significant difference between valproate and lithium (RRI 5%; RR 1.05; 95% C.I. 0.74-1.50) or between valproate and carbamazepine (RRR 34%; RR 0.66; 95% C.I. 0.38 to 1.16). Valproate was less effective than olanzapine (failure to achieve clinical response; RRI 25%; RR 1.25, 95% C.I. 1.01 to 1.54; average of 2.8 point less change on the Mania Rating Scale (95% CI 0.83 to 4.79). There were no significant differences in acceptability as measured by total number of subjects withdrawing from the study. There were significant differences in the side effect profiles of valproate and olanzapine, with more sedation and weight gain on olanzapine. REVIEWER'S CONCLUSIONS: There is consistent, if limited, evidence to suggest that valproate is an efficacious treatment for acute mania. Valproate may be less effective than olanzapine but may cause less sedation and weight gain. More well designed, randomised controlled trials investigating the relative efficacy and acceptability of valproate in the treatment of the full range of acute affective episodes occurring in bipolar disorder are required.

Antimanic Agents↗