Divalproex-ER pharmacokinetics in older children and adolescents

Preparation of Coated Valproic Acid and Sodium Valproate Sustained-release Matrix Tablets

The aim of this research was to investigate the technique for preparation of coated valproic acid and sodium valproate sustained-release matrix tablets. Different diluents were tested and selected as the effective absorbent for oily valproic acid. Effect of the amount of absorbent and hydroxypropylmethylcellulose on drug release from valproic acid-sodium valproate matrix tablets prepared with wet granulation technique was evaluated in pH change system. Colloidal silicon dioxide effectively adsorbed liquid valproic acid during wet granulation and granule preparation. The amounts of colloidal silicon dioxide and hydroxypropylmethylcellulose employed in tablet formulations affected drug release from the tablets. The drug release was prominently sustained for over 12 h using hydroxypropylmethylcellulose-based hydrophilic matrix system. The mechanism of drug release through the matrix polymer was a diffusion control. The drug release profile of the developed matrix tablet was similar to Depakine Chrono^®, providing the values of similarity factor (f2) and difference factor (f1) of 85.56 and 2.37, respectively. Eudragit^® L 30 D-55 was used as effective subcoating material for core matrix tablets before over coating with hydroxypropylmethylcellulose film with organic base solvent. Drug release profile of coated matrix tablet was almost similar to that of Depakine Chrono^®.

Divalproex extended-release in adolescent migraine prophylaxis: results of a randomized, double-blind, placebo-controlled study

OBJECTIVE

To evaluate the efficacy, tolerability, and safety of 3 different doses of divalproex sodium extended-release vs placebo in the prophylaxis of migraine headaches in adolescents.

BACKGROUND

Divalproex sodium has been approved for migraine prophylaxis in adults, and previous uncontrolled data suggest divalproex sodium may be effective in preventing migraine in children and adolescents with acceptable tolerability.

METHODS

This was a 12-week, phase 3, randomized, placebo-controlled, double-blind, parallel-group, multicenter study in approximately 300 adolescents aged 12 to 17 years with migraine headaches. At the end of the baseline phase, subjects still meeting study criteria were randomized in a 1:1:1:1 ratio to receive divalproex sodium extended-release 250 mg, 500 mg, or 1000 mg once daily, or placebo. The primary efficacy variable was reduction from baseline in 4-week migraine headache rate for each active treatment group vs placebo. Standard safety assessments were conducted and testosterone and sex hormone-binding globulin levels were collected for postmenarchal females.

RESULTS

There was no statistically significant treatment difference between any divalproex sodium extended-release dose group and placebo for the primary efficacy variable, reduction from baseline in 4-week migraine headache rate. There were no statistically significant differences in adverse events between any active treatment group and placebo. A notable dose-related decrease in platelets was observed, and individuals in all 4 treatment groups had increases in ammonia levels; treatment differences in other laboratory variables were generally small. Among postmenarchal female subjects who were not taking hormonal contraceptives or other steroids, there was no statistically significant change in testosterone levels, but a statistically significant dose-related increase in sex hormone-binding globulin was observed.

CONCLUSIONS

In the current study, divalproex sodium extended-release did not differentiate from placebo in the prophylactic treatment of migraine headaches but was generally well-tolerated in adolescents aged 12 to 17 years.

Once-daily dosing is appropriate for extended-release divalproex over a wide dose range, but not for enteric-coated, delayed-release divalproex: evidence via computer simulations and implications for epilepsy therapy

Divalproex sodium extended-release (divalproex-ER), administered once-daily, maintains plasma valproic acid (VPA) concentrations for 24h, whereas enteric-coated, delayed-release divalproex sodium (divalproex) requires multiple-daily doses to do the same. We hypothesize that a once-daily divalproex regimen should not be administered to epilepsy patients requiring high total daily doses, e.g., 35.6-56 mg/kg/day, due to the potential for high (>125 mg/L) maximum VPA concentrations (C(max)). We examined the impact of once-daily dosing, divalproex vs. divalproex-ER, on steady-state plasma VPA concentration-time profiles at commonly used doses in monotherapy (uninduced) and polytherapy (hepatic enzyme-induced) virtual adult patients. Only the 1125 mg once-daily divalproex dose had mean C(max)<100mg/L; >or=2000 mg produced mean C(max)>or=125 mg/L. Mean divalproex C(min) was approximately 50 mg/L at two of four doses tested, whereas mean ER C(min) was >73 mg/L at all doses tested. Once-daily divalproex peak-trough fluctuation was 4.4-6.2-fold greater than once-daily divalproex-ER. We predict that excursions beyond the conventional recommended VPA plasma concentration range will commonly occur with high total mg daily doses (>or=2000 mg) of enteric-coated divalproex, if dosed once-daily, potentially producing clinical toxicity. This divalproex formulation should not be dosed once-daily at high total mg daily doses due to this risk. Divalproex-ER is the appropriate formulation for administration on a once-daily basis, especially if large total mg/day doses are required for the control of seizure activity.

A double-blind, randomized, placebo-controlled trial of divalproex extended-release in the treatment of bipolar disorder in children and adolescents

OBJECTIVE

To compare the efficacy and safety of divalproex extended-release (ER) to placebo in a 28-day double-blind study of bipolar disorder in children and adolescents and evaluate the safety of divalproex ER in a 6-month open-label extension study.

METHOD

In the double-blind study, 150 patients (manic or mixed episode, aged 10-17 years) with baseline Young Mania Rating Scale (YMRS) score of 20 or higher were randomized to once-daily placebo or divalproex ER, which was titrated to clinical response or serum valproate concentration of 80 to 125 microg/mL. Sixty-six patients enrolled in the extension study.

RESULTS

In the double-blind study, a treatment effect was not observed with divalproex ER based on change in mean YMRS score (divalproex ER -8.8 [n = 74]; placebo -7.9 [n = 70]) or secondary measures. Divalproex was similar to placebo based on incidence of adverse events. Four subjects treated with divalproex ER and three treated with placebo discontinued because of adverse events. Mean ammonia levels increased in the divalproex ER group, but only one patient was symptomatic. In the long-term study, YMRS scores decreased modestly (2.2 points from baseline). The most common adverse events were headache and vomiting.

CONCLUSIONS

The results of the study do not provide support for the use of divalproex ER in the treatment of youths with bipolar I disorder, mixed or manic state. Further controlled trials are required to confirm or refute the findings from this study.

Adolescents in clinical trials

Drug development is a lengthy, costly, and complex process, with clinical trials essential for characterizing dosing, safety, and efficacy in treated populations. After regulatory approval, aggressive marketing ensures that most drugs are used by a broad spectrum of ages, genders, races, and ethnic groups. Unfortunately, not all groups are adequately represented in clinical trials; adolescents are commonly overlooked. This commentary explores how adolescents are considered during drug development, with a special focus on the influence of inherent psychosocial, biological, ethical, and regulatory issues in their recruitment and participation in clinical studies leading to drug licensing.

Divalproex sodium extended-release for the prophylaxis of migraine headache in adolescents: results of a stand-alone, long-term open-label safety study

OBJECTIVE

The objective of this long-term open-label study in adolescents was to assess the safety and tolerability of divalproex sodium extended-release in the prophylaxis of migraine headaches.

BACKGROUND

Two formulations of divalproex sodium have demonstrated efficacy in the prevention of migraine headaches in adults. However, no medications are currently approved for this indication in adolescents, and long-term safety data on agents for migraine prevention are lacking for this younger population. Therefore, the current study was conducted to assess the long-term safety and tolerability of divalproex extended-release in adolescents with migraine headaches.

METHODS

This was a 12-month, phase 3, open-label, multicenter study of adolescents aged 12 to 17 years with migraine headaches diagnosed by International Headache Society criteria. Divalproex sodium extended-release was initiated at 500 mg/day for 15 days then increased to 1000 mg daily, with subsequent adjustments permitted within a dosing range of 250-1000 mg daily. Study visits were conducted at days 1 and 15 and months 1, 2, 3, 6, 9, and 12. Safety was evaluated by adverse event collection, laboratory assessments, physical and neurological examinations, vital signs, electrocardiograms, the Udvalg for Kliniske Undersøgelser Side Effect Rating Scale, the Wechsler Abbreviated Scale of Intelligence, and the Behavioral Assessment Scale for Children. Efficacy was evaluated by following the number of migraine headache days reported in subjects' headache diaries over sequential 4-week intervals for the duration of the trial.

RESULTS

A total of 241 subjects were enrolled and treated. The most frequently reported adverse events were nausea (19%), vomiting (18%), weight gain (12%), nasopharyngitis (11%), migraine (10%), and upper respiratory tract infection (10%). Ten (4%) subjects experienced serious adverse events, and 40 (17%) subjects discontinued because of an adverse event. Increases in ammonia levels were observed. No other clinically significant changes were observed in laboratory values, vital signs, rating scales, or electrocardiograms. Median 4-week migraine headache days decreased 75% between the first and the fourth months of the study (from 4.0 to 1.0) and remained at or below this level for the remainder of the study.

CONCLUSIONS

In this long-term open-label study of adolescents with migraine, the safety and tolerability profile of divalproex sodium extended-release was consistent with findings from previous trials in adults, as well as 2 studies recently completed in adolescents. In general, divalproex sodium extended-release was well-tolerated in adolescents with migraine.

Valproic acid metabolism and its effects on mitochondrial fatty acid oxidation: a review

Valproic acid (VPA; 2-n-propylpentanoic acid) is widely used as a major drug in the treatment of epilepsy and in the control of several types of seizures. Being a simple fatty acid, VPA is a substrate for the fatty acid beta-oxidation (FAO) pathway, which takes place primarily in mitochondria. The toxicity of valproate has long been considered to be due primarily to its interference with mitochondrial beta-oxidation. The metabolism of the drug, its effects on enzymes of FAO and their cofactors such as CoA and/or carnitine will be reviewed. The cumulative consequences of VPA therapy in inborn errors of metabolism (IEMs) and the importance of recognizing an underlying IEM in cases of VPA-induced steatosis and acute liver toxicity are two different concepts that will be emphasized.

Valproate use in children and adolescents with bipolar disorder

This review aims to provide an update on valproate use in children and adolescents with bipolar disorder by summarising currently available clinical trials results. Guidelines for the treatment of type I bipolar disorder in children and adolescents, with or without psychotic features, recommend valproate, alone or in combination with an atypical antipsychotic, as a first-line treatment option; however, most randomised and open-label studies investigating valproate in paediatric populations have only evaluated a small number of participants. Therefore, the data from these studies need to be interpreted cautiously. A further complicating issue is the controversy surrounding the definition and diagnosis of bipolar disorders in this age group. Data suggest that valproate may be particularly useful for patients whose symptoms have not been responsive to lithium, or as part of combination therapy. Evidence from randomised controlled trials show that valproate monotherapy is associated with a Young Mania Rating Scale (YMRS) response rate (percentage of patients with a reduction in YMRS score from baseline to endpoint of >/=50%) of 53%, while combination therapy with valproate plus quetiapine is associated with a YMRS response rate of 87%; however, placebo response rates were high, emphasising the need for caution when interpreting data from open-label trials. At present, data supporting the efficacy and safety of mood stabilisers for the treatment of bipolar disorders in children and adolescents are limited; therefore, well designed, randomised controlled clinical studies are needed to identify and confirm the potential roles of valproate in children and adolescents with bipolar disorders, particularly in those with psychiatric co-morbidities. Furthermore, clinical studies are required to clarify the efficacy and tolerability profile of valproate in comparison with other agents used in paediatric and adolescent bipolar disorder.

Extended-release formulations in epilepsy

In the past years, the extended-release antiepileptic drug formulations have been developed and then approved for the treatment of many types of epilepsy. Among these extended-release formulations of antiepileptic drugs, the main drugs are valproic acid, carbamazepine, and phenytoin. This review analyzes the chemical and structural characteristics of the extended-release formulations of these 3 antiepileptic drugs, analyzing their bioequivalence and the studies about their clinical use. The results of these studies are encouraging and suggest a good tolerability and efficacy of these extended-release formulations, although larger studies are needed.

Progress report on new antiepileptic drugs: a summary of the Eigth Eilat Conference (EILAT VIII)

The Eigth Eilat Conference on New Antiepileptic Drugs (AEDs)-EILAT VII, took place in Sitges, Barcelona from the 10th to 14th September, 2006. Basic scientists, clinical pharmacologists and neurologists from 24 countries attended the conference, whose main themes included a focus on status epilepticus (epidemiology, current and future treatments), evidence-based treatment guidelines and the potential of neurostimulation in refractory epilepsy. Consistent with previous formats of this conference, the central part of the conference was devoted to a review of AEDs in development, as well as updates on marketed AEDs introduced since 1989. This article summarizes the information presented on drugs in development, including brivaracetam, eslicarbazepine acetate (BIA-2-093), fluorofelbamate, ganaxolone, huperzine, lacosamide, retigabine, rufinamide, seletracetam, stiripentol, talampanel, valrocemide, JZP-4, NS1209, PID and RWJ-333369. Updates on felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine and new extended release oxcarbazepine formulations, pregabalin, tiagabine, topiramate, vigabatrin, zonisamide and new extended release valproic acid formulations, and the antiepileptic vagal stimulator device are also presented.

Every-12-hour administration of extended-release divalproex in patients with epilepsy: impact on plasma valproic acid concentrations

Extended-release divalproex sodium (divalproex-ER) biopharmaceutics after every-12-hour (q12h) administration was compared with that of once-daily divalproex-ER and conventional divalproex given every 6 hours (q6h) in a multiple-dose (14-day), randomized, three-period crossover design study in 24 patients with epilepsy concomitantly receiving enzyme-inducing antiepileptic medication(s). Plasma valproic acid (VPA) minimum concentration (Cmin) for divalproex-ER q12h was higher than the once-daily divalproex-ER Cmin (P=0.043). Once-daily divalproex-ER Cmin values were not different from those for divalproex q6h, suggesting that adequate trough steady-state concentrations are maintained with once daily dosing, despite enzyme-inducing comedication. The degree of peak-trough fluctuation (DFL, calculated as (Cmax-Cmin)/Cavg) in VPA concentration was less with both q12h (35.2% less) and once-daily (16.9% less) divalproex-ER regimens compared with q6h divalproex (P0.024). The DFL for divalproex-ER dosed as a q12h regimen was 22% less than that for once-daily divalproex-ER (P=0.02). The DFL in VPA concentration with divalproex-ER can be minimized with once-daily administration and more so with q12h administration, compared with conventional enteric-coated divalproex taken q6h.

Extended-release Divalproex in Child and Adolescent Outpatients with Epilepsy

PURPOSE

To determine whether valproic acid [divalproex (DVP)] extended-release, administered at a higher proportionate once-daily dosage, can be safely substituted for delayed-release or sprinkle in pediatric patients with epilepsy.

METHODS

Patients between ages 6 and 17 years with stable epilepsy taking DVP were randomized to 7 days of either DVP delayed-release/sprinkle (at the usual daily dose taken before study entry) or extended-release DVP (daily dose, 8% to 25% higher than their usual dose), and then (crossed over to) 7 days of the comparator formulation. Patient's clinical status was evaluated at a screening visit and on days 8 and 15, and with telephone follow-up 1 month after study completion.

RESULTS

No statistically significant difference in mean plasma VPA levels measured at the end of treatment was observed: 99, 92, and 103 mug/ml with the delayed-release tablets (n = 4), the sprinkle formulation (n = 11), and the extended-release tablets (n = 16), respectively. Seizure-control rates were stable during patients' use of the extended-release formulation. None of the study patients experienced a treatment-related adverse event.

CONCLUSIONS

The total daily dose for patients taking the delayed-formulation may need to be increased by < or = 20% when they are switched to the extended-release formulation. When switching from sprinkles to the extended-release formulation, individual variability must be considered. In patients who have VPA levels near the very high end of the therapeutic range (>100 microg/ml), it may be more prudent to make only minor modifications to the total daily dose during conversion and then to individualize the DVP extended-release dose based on plasma levels.

Comparison of the bioavailability of 250 and 500 mg divalproex sodium extended-release tablets in healthy volunteers

Divalproex sodium extended-release tablet (divalproex-ER), 500 mg strength, is approved for use in the prophylaxis of migraine headaches and epilepsy. The bioavailability of novel 250 mg divalproex-ER formulations, under development to allow greater flexibility in dosing, was compared with the available 500 mg divalproex-ER in a single-dose, fasting and nonfasting, randomized, open-label, crossover study in healthy adult volunteers. One group of 15 subjects was dosed after a 10 h overnight fast and another group of 24 subjects was dosed after a high-fat breakfast. Plasma valproic acid concentration-time profiles were used to assess pharmacokinetics. Bioequivalence assessments were made via the 90% confidence interval for maximum plasma valproic acid concentration (C(max)) and the area under the concentration-time curve from time zero to infinity (AUC(infinity)). The relative bioavailability point estimates (90% confidence interval) for C(max) and AUC(infinity) were 1.05 (0.94-1.16) and 0.95 (0.83-1.09) under fasting conditions, and 1.01 (0.91-1.12) and 0.97 (0.87-1.08) under nonfasting conditions, respectively. The test 250 mg tablet formulation was bioequivalent to the reference 500 mg tablet formulation, under both fasting and nonfasting conditions, as the 90% confidence intervals for both C(max) and AUC(infinity) were within the 0.80-1.25 interval.

Clinical comparison of extended-release divalproex versus delayed-release divalproex: pooled data analyses from nine trials

Divalproex sodium is an effective anticonvulsant, antimanic, and migraine prophylaxis agent. Recently, a new extended-release (ER) formulation of divalproex sodium has become available, which allows for once-daily dosing and provides prolonged therapeutic serum levels. Using data pooled from nine open-label trials involving 321 epilepsy and psychiatry patients, we compared the efficacy and tolerability of divalproex ER with preceding treatment with the older delayed-release (DR) formulation, based on patient reports and analysis by McNemar's test for within-subject paired data. Divalproex ER was associated with superior tolerability with less frequent tremor, weight gain, and gastrointestinal complaints (all P<0.001), but not less hair loss. Divalproex ER also yielded improved seizure control and greater improvement of psychiatric symptoms, and was greatly preferred by patients over divalproex DR. Although the results of the current analyses must be considered highly tentative due to the open-label nature of the trials included, the findings do suggest broad clinical superiority of the new ER preparation.

Progress report on new antiepileptic drugs: a summary of the Seventh Eilat Conference (EILAT VII)

The Seventh Eilat Conference on New Antiepileptic Drugs (AEDs) (EILAT VII) took place in Villasimius, Sardinia, Italy from the 9th to 13th May 2004. Basic scientists, clinical pharmacologists and neurologists from 24 countries attended the conference,whose main themes included advances in pathophysiology of drug resistance, new AEDs in pediatric epilepsy syndromes, modes of AED action and spectrum of adverse effects and a re-appraisal of comparative responses to AED combinations. Consistent with previous formats of this conference, the central part of the conference was devoted to a review of AEDs in development, as well as updates on second-generation AEDs. This article summarizes the information presented on drugs in development, including atipamezole, BIA-2-093, fluorofelbamate, NPS 1776, pregabalin, retigabine, safinamide, SPM 927, stiripentol, talampanel,ucb 34714 and valrocemide (TV 1901). Updates on felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, tiagabine,topiramate, vigabatrin, zonisamide, new oral and parenteral formulations of valproic acid and SPM 927 and the antiepileptic vagal stimulator device are also presented.

Extended-release formulations: simplifying strategies in the management of antiepileptic drug therapy

Advances in our understanding, diagnosis, and treatment of seizure disorders have transformed the management of epilepsy. As the number of antiepileptic drugs and their formulations increase, so do the expectations of therapy. Once limited to attaining complete control of seizures, epilepsy management now strives to enable patients to lead lifestyles consistent with their own capabilities. Extended-release antiepileptic drug formulations can help achieve the primary treatment goals for many patients with epilepsy: preventing occurrence of seizures and preventing or reducing side effects. The dosing flexibility and consistency of serum levels (without marked peak-to-trough fluctuations) conferred by extended-release formulations help achieve these goals. These same attributes of extended-release formulations may also improve compliance, quality of life, and patient satisfaction with treatment.