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PubMed2003

Chronic treatment with lithium, but not sodium valproate, increases cortical N-acetyl-aspartate concentrations in euthymic bipolar patients.

Previous studies have found that treatment with lithium over a 4-week period may increase the concentration of N-acetyl-aspartate (NAA) in both bipolar patients and controls. In view of other findings indicating that NAA concentrations may be a good marker for neuronal viability and/or functioning, it has been further suggested that some of the long term benefits of lithium may therefore be due to actions to improve these neuronal properties. The aim of the present study was to utilize H magnetic resonance spectroscopy ( H MRS) to further examine the effects of both lithium and sodium valproate upon NAA concentrations in treated euthymic bipolar patients. In the first part of the study, healthy controls (n =18) were compared with euthymic bipolar patients (type I and type II) who were taking either lithium (n =14) or sodium valproate (n =11), and NAA : creatine ratios were determined. In the second part, we examined a separate group of euthymic bipolar disorder patients taking sodium valproate (n =9) and compared these to age- and sex-matched healthy controls (n =11), and we quantified the exact concentrations of NAA using an external solution. The results from the first part of the study showed that bipolar patients chronically treated with lithium had a significant increase in NAA concentrations but, in contrast, there were no significant increases in the sodium valproate-treated patients compared to controls. The second part of the study also found no effects of sodium valproate on NAA concentrations. These findings are the first to compare NAA concentrations in euthymic bipolar patients being treated with lithium or sodium valproate. The results support suggestions that longer-term administration of lithium to bipolar patients may increase NAA concentrations. However, the study suggests that chronic administration of sodium valproate to patients does not lead to similar changes in NAA concentrations. These findings suggest that sodium valproate and lithium may not share a common mechanism of action in bipolar disorder involving neurotrophic or neuroprotective effects.

Adult↗

PubMed1999

Prediction of valproate serum concentrations in adult psychiatric patients using Bayesian model estimations with NPEM2 population pharmacokinetic parameters.

Valproate serum concentrations between 45 and 125 microg/mL are associated with the drug's efficacy in acute mania. Adaptive control dosing of valproate has not been fully studied in psychiatry. The objective of this study was to derive population pharmacokinetic (PK) parameters for valproate in healthy volunteers and to test the ability of these PK parameters to estimate concentrations in adult psychiatric patients using a Bayesian program. Population PK parameters for oral valproate were estimated from 18 PK studies in six healthy volunteers (1) using NPEM2. A Bayesian PK program using these population parameters was used to predict valproate concentration-time points in a second cohort of 21 adult psychiatry patients using 0, 1, or 2 prior concentrations. Estimated population parameters (mean +/- SD) were: Ka, 1.15+/-1.75/h; V, 0.14+/-0.042 L/Kg; and CL, 0.902+/-0.133 L/h. Bayesian valproate estimations using these parameters were negatively biased (underestimations) using zero prior concentration and unbiased using 1 or 2 prior concentrations. Mean error values (95% CI) in microg/mL for predictions using 0, 1, or 2 prior concentration-time points were -12.0 (-22.5, -1.5), -9.5 (-19.1, 0.1), and -2.5 (-11.1, 6.1), respectively, and mean absolute error values in microg/mL (95% CI) were 19.8 (12.6, 27.1), 16.3 (9.4, 23.3), and 10.1 (4.9, 15.2), respectively. Population parameters derived from healthy adult volunteers provided biased predictions of valproate concentrations in adult psychiatric patients. However, estimates using 1 or 2 valproate concentration time points predicted future concentrations that were precise and unbiased, given the wide therapeutic target range.

Adaptation, Physiological↗

PubMed1994

Decreased plasma protein binding of valproate in patients with acute head trauma.

1. One hundred and ten plasma samples were obtained from 50 patients treated with valproate for prophylaxis of post-traumatic head injuries. The samples were selected to include a wide range of albumin concentrations and were assayed for free and total valproate concentrations. Valproate binding parameters were determined from the Scatchard equation for one binding site using reweighted least squares analysis. 2. Plasma albumin concentrations were measured in 130 patients with head trauma. They started to decrease immediately after trauma, reaching a minimum at 5-7 days of approximately 24% of baseline value and did not return to normal until 1 month. 3. The free fraction of valproate varied six to seven-fold as albumin concentration ranged from 1.5 to 4.8 g 100 ml-1 (218-696 mumol l-1). The mean association constant for binding (Ka) was 0.008 mumol l(-1) and the mean number of binding sites (N) was 2.0. There values were similar to those reported for valproate in otherwise healthy patients with epilepsy. 4. Because of saturable protein binding of valproate, hypoalbuminaemia may necessitate the monitoring of free valproate concentrations to avoid toxicity when valproate is used in patients with acute head injury.

Acute Disease↗

PubMed1988

Is valproate monotherapy a practical possibility in chronically uncontrolled epilepsy?

In a prospective open study of 20 male epileptic residents of a mental handicap institution, polytherapy was gradually reduced to valproate monotherapy in 18 subjects. In terms of seizure frequency this was significantly disadvantageous but when carbamazepine was added or substituted, seizure control improved significantly. Drugs with documented adverse effects on cognitive function such as phenobarbitone and phenytoin were phased out. In the 18 subjects who achieved valproate monotherapy, no association between serum levels and seizure control could be demonstrated. Adverse effects of valproate were pancreatitis and thrombocytopenia; in one subject thrombocytopenia appeared to be associated with levels in the toxic range but in six other subjects 'toxic' levels of valproate did not give rise to any clinically detectable toxic signs. There was no instance of tremor or weight gain. It was concluded that, in the population studied (institutionalized patients with chronically uncontrolled seizures) valproate monotherapy was inappropriate but carbamazepine with or without valproate was a better option. Phasing out phenytoin and phenobarbitone was successful. Valproate serum levels did not contribute significantly to the conduct of the study; no general relationship between valproate serum levels and either seizure control or toxicity could be demonstrated.

Anticonvulsants↗

PubMed1995

Peripheral GABAA receptor-mediated effects of sodium valproate on dural plasma protein extravasation to substance P and trigeminal stimulation.

1. The GABA transaminase inhibitor and activator of glutamic acid decarboxylase, valproic acid is being used for the treatment of migraine. Its mechanism of action is unknown. We tested the effects of sodium valproate and GABAA-agonist muscimol on dural plasma protein ([125I]-bovine serum albumin) extravasation evoked by either unilateral trigeminal ganglion stimulation (0.6 mA, 5 ms, 5 Hz, 5 min) or substance P (SP) administration (1 nmol kg-1,i.v.) in anaesthetized Sprague-Dawley rats. 2. Intraperitoneal (i.p.) injection of sodium valproate or muscimol, but not baclofen (< or = 10 mg kg-1, i.p.) dose-dependently reduced dural plasma protein extravasation caused either by electrical trigeminal stimulation (ED50: 6.6 +/- 1.4 mg kg-1, i.p., and 58 +/- 18 micrograms kg-1, i.p. for valproate or muscimol, respectively) or by intravenous substance P administration (ED50: 3.2 +/- 1.4 mg kg-1, i.p. and 385 +/- 190 micrograms kg-1, i.p. for valproate or muscimol, respectively). 3. Valproate (6.6 mg kg-1, i.p.) or muscimol (58 micrograms kg-1, i.p.) had no effect on mean arterial blood pressure or heart rate when measured for 30 min after i.p. administration. 4. The GABAA-antagonist bicuculline (0.01 mg kg-1, i.p.) completely reversed the effect of valproate and muscimol on plasma extravasation following electrical stimulation or substance P administration, whereas the GABAB-receptor antagonist, phaclofen (0.01-1 mg kg-1, i.p.) did not. Bicuculline or phaclofen, given alone, did not alter the plasma extravasation response after either electrical stimulation or SP administration. 5. Valproate decreased plasma extravasation following substance P administration in adult animals, neonatally treated with capsaicin by a bicuculline-reversible mechanism. This suggests that GABAA receptors are not found primarily on those afferent neurones or fibres which are sensitive to capsaicin treatment in neonatal rats.6. We conclude that sodium valproate blocks plasma extravasation in the meninges through GABAA mediated postjunctional receptors probably within the meninges. The dosages required are comparable to those used clinically. Agonists and modulators at the GABAA receptor may become useful for the development of selective therapeutic agents for migraine and cluster headache.

Animals↗

PubMed2006

Role of valproate across the ages. Treatment of epilepsy in adults.

A workshop was held in Göteborg in June 2005 to discuss the place of valproate in treating adult epilepsies. Consensus positions were developed on the epilepsy types for which the drug is most suitable and the use of valproate in women of child-bearing age, in men and in patients with psychiatric comorbidity. Valproate was considered to be effective across a broad variety of epilepsy syndromes and seizure types and should be considered a suitable choice for first-line monotherapy of juvenile myoclonic epilepsy and other idiopathic generalized epilepsies. The use of valproate by women of child-bearing age is associated with potential harm to the foetus. A conservative approach to treatment is recommended in these patients whereby alternative antiepileptic drugs should be proposed to women planning pregnancies wherever satisfactory seizure control can be thereby maintained. In cases where valproate is used during pregnancy, either because the pregnancy was unplanned or because alternative treatment options of equivalent efficacy are unavailable, appropriate counselling, precautionary measures and monitoring should be provided. The evidence for an impact of valproate on male reproductive health is equivocal and considerations of male fertility should not be taken into account in deciding whether to prescribe valproate to men. Valproate can be proposed safely to patients with comorbid psychiatric disease or underlying psychiatric vulnerability.

Adult↗

PubMed2005

Valproate in bipolar disorder: 2000 onwards.

OBJECTIVE: To describe the evidence for the efficacy and tolerability of valproate in treatment of bipolar disorders, as well as factors associated with favorable or unfavorable outcomes. METHOD: Studies published from 2000 onwards were reviewed, as well as published abstracts. For clinical trials, randomized, prospective studies were emphasized. RESULTS: Several mechanisms of action of valproate on central nervous system neurons that may be relevant to its actions in bipolar disorders have been recently reported. These include inhibition of glycogen synthase kinase and activation of extracellular signal-regulated kinase. Several of the actions overlap those observed from lithium. Valproate is effective in treatment of mania, and somewhat more effective in certain patient subgroups than other treatments, e.g. mixed mania, and mania with prominent irritability. Valproate is comparable with olanzapine in maintenance treatment, and somewhat better tolerated. Higher serum levels, particularly above 110 microg/ml, are associated with more reports of weight gain, sedation, and reductions in platelet count. Valproate may be associated with an increased rate of polycystic ovarian syndrome, with increased weight contributing to the risk. Valproate reduces total cholesterol levels, particularly among patients with baseline elevations of cholesterol. Several studies indicate that valproate can be beneficially combined with antipsychotic drugs and other treatments for bipolar disorder. CONCLUSION: Valproate continues to be studied in further clarification of its mechanisms, efficacy, risks, and spectrum of benefits in bipolar disorder. It is a major treatment for bipolar disorder, both in monotherapy and combination therapy regimens.

Antimanic Agents↗

PubMed2000

Neonatal hypoglycaemia and withdrawal symptoms after exposure in utero to valproate.

AIMS: To define, in a prospective study, the risk of hypoglycaemia-defined as blood glucose concentration < 1.8 mmol/l-in term infants exposed in utero to valproate and to describe the withdrawal symptoms. METHODS: Twenty epileptic women were treated with valproate only during pregnancy and two were treated with valproate and carbamazepine. In the first trimester, the daily median dose of valproate was 1.0 g (range 0.3-4.2) and in the third trimester 1.2 g (range 0.3-4.8). RESULTS: Thirteen of the 22 infants became hypoglycaemic. One infant had eight episodes of hypoglycaemia, one had three episodes, two had two episodes, and nine had one episode each. The lowest blood glucose concentration was 1.0 mmol/l. All episodes were asymptomatic. The maternal mean plasma concentration of total valproate during the third trimester correlated negatively with blood glucose concentration one hour after delivery (p < 0.0003) and with the development of hypoglycaemia (p < 0.0001). There was no evidence for hyperinsulinaemia as the cause of hypoglycaemia. Ten infants developed withdrawal symptoms, which correlated positively with the mean dose of valproate in the third trimester and the concentration of the free fraction of valproate in maternal plasma at delivery (p < 0.02). CONCLUSIONS: Infants exposed to valproate in utero had a significantly elevated risk of hypoglycaemia, and withdrawal symptoms were often observed.

Anticonvulsants↗

PubMed1994

A multicentre comparative trial of sodium valproate and carbamazepine in adult onset epilepsy. Adult EPITEG Collaborative Group.

The long-term efficacy and safety of sodium valproate and carbamazepine in adult outpatients with newly diagnosed primary generalised or partial and secondarily generalised seizures were compared in a randomised, open, multicentre study at 22 neurology outpatient clinics. Patients were randomised to oral sodium valproate (Epilim EC enteric coated 200 mg tablets twice daily, n = 149) or oral carbamazepine (100 mg twice daily increasing to 200 mg twice daily in week 2, n = 151) and followed up for three years. If clinically necessary, dosages were regularly increased until seizures were controlled or toxicity developed. Sodium valproate and carbamazepine controlled both primary generalised and partial seizures equally effectively overall. Significantly more patients on sodium valproate than carbamazepine (126/140 (90%) v 105/141 (75%), p = 0.001) remained on randomised treatment for at least six months. Skin rashes occurred significantly more often in carbamazepine recipients than in sodium valproate recipients (11.2% v 1.7%, p < 0.05) and carbamazepine was associated with a higher withdrawal rate because of adverse events (15% v 5% on sodium valproate) in the first six months of treatment. There was no difference between the drugs in the rate of withdrawal because of poor seizure control at any stage, regardless of seizure type. At the end of the three year trial period, over 70% of the available patients were still on randomised treatment or had recently stopped treatment after achieving full seizure control. Sodium valproate and carbamazepine were both associated with a high degree of overall seizure control regardless of seizure type and both have good long-term tolerability in adult patients with newly diagnosed epilepsy. Recommendations are made for a higher initial dosage regime for sodium valproate in partial seizures.

Administration, Oral↗

PubMed1993

Valproate as a loading treatment in acute mania.

Evidence from earlier studies indicates that the antimanic action of valproate becomes most apparent within 1-4 days of achieving serum concentrations 50 micrograms/ml, that valproate can be orally loaded with achievement of therapeutic serum concentrations within the first several days of treatment, there is a rapid onset of response, and minimal side effects. To provide further data on the safety and efficacy of valproate oral loading in the treatment of acute mania, we evaluated 13 consecutive patients with acute manic syndromes who received valproate initiated at a dosage of 20 mg/kg/day. In most cases, valproate was added to other psychotropics. All 13 patients received at least 5 full days of valproate maintained at or above 20 mg/kg/day, and valproate serum concentrations were 50 micrograms/ml (mean +/- SD = 88 + 25) by the second or third day of treatment. Ten (77%) patients displayed a moderate or marked response. Side effects were infrequent and minor. Consistent with our earlier study, these findings suggest that valproate can be safely administered via a loading dose of 20 mg/kg/day to patients with acute mania, including those on other psychotropics, and that it may produce a rapid response with minimal side effects.

Acute Disease↗

PubMed2006

Linear relationship of valproate serum concentration to response and optimal serum levels for acute mania.

OBJECTIVE: Several studies have shown that achieving adequate serum valproate levels is critical to rapid stabilization of acute mania, but estimates of the target therapeutic level have been imprecise. A post hoc analysis of pooled intent-to-treat data from three randomized, placebo-controlled studies of divalproex treatment for acute mania was performed to test a hypothesized linear relationship between serum concentration and response and to determine optimal blood levels for treatment of acute mania. METHOD: Subjects (N=374) were stratified into seven groups (six valproate serum level ranges and placebo), and effect size was determined for each. Linearity of dose response was tested with both parametric and nonparametric techniques. ANOVA was used to compare the response at each serum level range with that of placebo as well as the lowest valproate level (< =55.0 microg/ml). The mean serum valproate level was then determined for all subjects with an effect size greater than or equal to the maximal effect derived from linear modeling. RESULTS: The fit of blood level and response to a linear model was good. Efficacy was significantly greater than placebo beginning at the 71.4-85.0 microg/ml range and for all higher valproate levels; the 94.1-107.0 and >107.0 microg/ml groups were superior to the lowest valproate serum level group. The effect size associated with highest serum levels (>94 microg/ml) was 1.06 (0.59 after placebo correction). Subjects obtaining this effect or greater (N=84) had a mean serum level of 87.5 microg/ml. Blood levels in the lowest effective range were 60% more effective than placebo and in the higher ranges were 120% more effective. Tolerability appeared similar for all groups. CONCLUSIONS: The results of this study suggest that there is a linear relationship between valproate serum concentration and response and that the target blood level of valproate for best response in acute mania is above 94 microg/ml.

Acute Disease↗

PubMed1989

Effect of sodium valproate on the secretion of proopiomelanocortin derived peptides from cultured rat anterior pituitary cells.

We examined effects of sodium valproate, a gamma amino butyric acid (GABA)-transaminase inhibitor, on the secretion of immunoreactive (IR)-ACTH and IR-beta-endorphin/LPH from cultured rat anterior pituitary cells to determine whether sodium valproate has a direct action on the secretion of ACTH and its related peptides from the cultured rat anterior pituitary gland. During the 3 h incubation, the basal secretion of IR-ACTH and IR-beta-endorphin/LPH decreased to 50.8% and 58.3%, respectively, of the control concentration after adding 10(-7) M sodium valproate into the incubation media and to 67.7% and 69.3%, respectively, of the control levels with 10(-8) M sodium valproate. However, sodium valproate at a concentration of 10(-6) M or 10(-9) M did not affect the basal concentration of IR-ACTH and IR-beta-endorphin/LPH. Sodium valproate at a concentration of 10(-7) M significantly attenuated the stimulated release of IR-ACTH and IR-beta-endorphin/LPH by 10(-9) or 10(-10) M of ovine corticotrophin releasing factor. These results indicate that sodium valproate could directly effect rat anterior pituitary cells to suppress both basal and stimulated release of proopiomelanocortin derived peptides and this supports the hypothesis that sodium valproate has a direct effect at the pituitary corticotroph in reducing plasma ACTH.

Adrenocorticotropic Hormone↗

PubMed1996

Effects of valproate-induced alteration of the GABAergic system on pulsatile luteinizing hormone secretion in ovariectomized women.

It is well established that valproate increases hypothalamic concentrations of gamma-aminobutyric acid (GABA). Although little research has been done on the role of GABA in the control of pulsatile luteinizing hormone (LH) secretion in humans, our group recently found that administration of valproate had no significant effect on pulsatile LH secretion in late follicular and mid-late luteal phase normal women. However, the results of several studies of rats suggest that GABAergic regulation of LH secretion may depend on steroid levels. The objective of this work was to determine whether regular administration of sodium valproate inhibits pulsatile LH secretion in ovariectomized women. Twelve women who had undergone ovariectomy for causes other than malignant tumors were each studied in two 8 h sessions, in each of which blood samples were taken every 5 min. The first session was the control; for the second. 400 mg of sodium valproate was administered every 8 h during the seven preceding days and at 08.00 h and 14.00 h on the day of the study session. Serum valproate was determined by repolarization fluorescence spectrophotometry, and LH, estradiol and progesterone by radioimmunoassay. The serum LH series were subjected to a deconvolution procedure to reconstruct the pattern of pituitary LH secretion. Luteinizing hormone pulses were identified by the authors' non-parametric method. Control and post-valproate results were compared with regard to number of pulses, pulse duration, the quantity of LH secreted in each pulse, interpulse interval and mean serum LH level. There was no statistically significant difference between control and post-valproate results for any of the variables considered. It is concluded that sustained serum valproate levels do not alter pulsatile secretion of LH in ovariectomized women. This implies that, in humans, GABA is probably not a decisive factor in the regulation of the GnRH pulse generator.

Adult↗

PubMed2007

Spectrum of effectiveness of valproate in neuropsychiatry.

Valproate is principally effective in manic aspects of bipolar disorder. Tolerability has been somewhat more favorable for valproate than comparators, with the frequent adverse effects being gastrointestinal disturbances and weight gain. Total cholesterol and low-density lipoproteins are reduced by valproate. Valproate is effective and well tolerated when combined with lithium or antipsychotic drugs. Valproate is efficacious in mixed and euphoric mania. In studies of maintenance versus placebo and active comparators, patients initially treated with divalproex for mania had more robust long-term benefits than in the full sample analyses. In maintenance treatment, patients whose valproate serum levels were between 75 and 99 microg/ml had longer time to discontinuation for any reason or a new mood episode than did patients receiving placebo. The profile of utility in bipolar disorders is principally for core features of manic symptomatology (e.g., impulsivity, hyperactivity and irritability), with little evidence of benefit for anxiety or psychosis. Valproate appears useful in other disorders that have behavioral dimensions inclusive of the domains that valproate benefits in bipolar disorders, such as schizophrenia.

Antimanic Agents↗

PubMed1999

Efficacy of lithium vs. valproate in the treatment of mania in the elderly: a retrospective study.

BACKGROUND: This retrospective study was conducted to assess the efficacy of lithium and valproate and associated serum levels in the treatment of mania in elderly patients. METHOD: Records of 59 patients aged 55 years and older with minimal or no neurologic impairment, hospitalized for mania, and discharged on lithium (N = 30) or valproate (N = 29) therapy were reviewed. Data on mood stabilizer choice, serum levels, and type of mania were recorded. A clinician blinded to medications rated improvement in each case with Clinical Global Impressions (CGI) scores based on abstracted notes. RESULTS: Overall, the percentage of patients improved was significantly greater in the lithium group than in the valproate group (67% vs. 38%, chi2 = 4.88, p = .027). Patients taking lithium with serum levels > or =0.8 mmol/L were more improved at discharge than those outside this range (> or =0.8, CGI 2.0+/-0.6 vs. <0.8, CGI 2.6+/-0.8, t = 2.15, p = .043). Patients taking valproate with serum levels between 65-90 microg/mL were more improved at discharge than those outside this range (65-90, CGI 2.1+/-0.6 vs. <65, >90, CGI 3.3+/-0.8, t = 3.73, p = .002). When response rates among only patients with these "therapeutic" levels were assessed, they were similar for lithium (82%) and valproate (75%). The difference in efficacy between drugs was maintained in classic mania, but the 2 drug groups were similar when only mixed mania was analyzed (lithium 63% vs. valproate 67% improved). CONCLUSION: Results suggest that lithium may be more efficacious than valproate overall, but response rates for the 2 drugs were similar when "therapeutic" serum levels were achieved. For lithium, levels similar to those reported for younger adults were associated with response. For valproate, a "therapeutic window" different from that in younger adults was found. While the retrospective and naturalistic design of this study has limitations, these data may help direct further studies and treatment of mania in the elderly.

Age Factors↗

PubMed1998

Valproate in the treatment of epilepsy in people with intellectual disability.

Valproate is a major broad-spectrum antiepileptic drug effective against many different types of epileptic seizures. Valproate is a first-line drug in the treatment of primary generalized seizures and syndromes, but it is also effective in other seizure and epilepsy types. The possible mechanisms of action and the pharmacokinetics of valproate are outlined. A limited number of studies on the efficacy and safety of valproate treatment in patients with West syndrome and Lennox-Gastaut syndrome have shown that even therapy-resistant people with intellectual disability can benefit from add-on valproate medication. In status epilepticus, valproate can be effective either intravenously, by gastric drip or following rectal administration. Patient tolerance towards valproate is generally good. The most serious adverse effect of valproate include hepatotoxicity and teratogenicity.

Anticonvulsants↗

PubMed1999

Pharmacokinetic characteristics of a new multiple unit sustained release formulation of sodium valproate.

AIM: Two bioavailability studies were conducted in healthy male volunteers to determine the absorption characteristics of a new dosage form of sodium valproate consisting of sustained release pellets in a hard gelatine capsule. SUBJECTS, MATERIAL AND METHODS: To obtain first data on the in vivo behavior of the new multiple unit formulation a single dose pilot study in comparison with an oral solution was performed in 6 volunteers. Following the pilot study the pharmacokinetics were investigated versus a conventional enteric-coated tablet after multiple dosing in 18 volunteers. The volunteers were administered either a single or multiple dose of 300 mg sodium valproate. In both studies a wash-out period of at least 1 week elapsed between the periods. Valproic acid was determined from serum by gas chromatography at intervals suitable for obtaining concentration time curves for both regimens. RESULTS: The results of the pilot study showed that the valproate concentration in serum following administration of the new sustained release capsule increased smoothly and a longer lasting plateau was observed as compared with the solution. The average maximum serum valproate concentration of 12.5 microg/ml (sustained release capsule) and 24.3 microg/ml (solution) appeared at 9.3 h and 0.58 h after dosing. The extent of valproate absorption as reflected in the AUC data for each formulation was equivalent for the new sustained release capsule and reference formulation (AUC0-infinity: 369 +/- 88.9 and 339 +/- 76.2 microg/ml x h). Data obtained after multiple dose administration provided an indication of the consistency of valproate absorption from each dosage form. The time concentration profiles following twice daily administration of 300 mg sodium valproate in the multiple dose study showed that the extent parameters for absorption of valproate (AUC(8tau9tau) = 842 +/- 166 microg/ml x h) are equivalent with the enteric-coated preparation (AUC(8tau9tau) = 823 +/- 139 microg/ml x h). However, the fluctuation of the new sustained release formulation (PTF(8tau9tau) = 0.33 +/- 0.09) is about only one third of the fluctuation observed with the enteric-coated formulation (PTF(8tau9tau) = 0.88 +/- 0.22) when administered twice daily. CONCLUSION: These data indicate that the new sustained release capsule possesses desirable absorption characteristics in a form that allows twice daily or even once daily dosing and therefore improves patient compliance.

Adult↗

PubMed2003

Pharmacokinetics, drug interactions, and tolerability of valproate.

Valproate is a branched-chain carboxylic acid with an extensive history of use as an antiepileptic drug. In recent years, multiple uses for valproate have been found in psychiatry. As divalproex sodium, it is currently approved for the treatment of manic episodes associated with bipolar disorder and for migraine headache prophylaxis. Accumulating evidence suggests it may also be beneficial in several anxiety disorders. Valproate's pharmacokinetic profile has been extensively studied, mostly within the context of treatment of epilepsy. This review summarizes valproate's pharmacokinetics, drug interactions, and tolerability as an aid to promote individualized pharmacotherapy. Valproate is characterized by dose-limited absorption, nonlinear plasma protein binding, and multiple metabolic pathways of elimination. Pharmacokinetic drug interactions involving valproate result from its susceptibility to the effects of both enzyme induction and inhibition, along with an ability for weak to moderate inhibition of the metabolic elimination of other drugs. Valproate has an extensive record of use across the lifespan and a good record of tolerability. Some precautions are warranted in its use, but valproate is generally safe whether administered alone or in combination with other therapies.

Animals↗