Valproic acid capsule delayed release clinical studies
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Clinical Studies
14.1 Mania
The effectiveness of valproate for the treatment of acute mania was demonstrated in two 3-week, placebo controlled, parallel group studies.
(1) Study 1: The first study enrolled adult patients who met DSM-III-R criteria for bipolar disorder and who were hospitalized for acute mania. In addition, they had a history of failing to respond to or not tolerating previous lithium carbonate treatment. Valproate was initiated at a dose of 250 mg TID and adjusted to achieve serum valproate concentrations in a range of 50-100 mcg/mL by day 7. Mean valproate doses for completers in this study were 1118, 1525, and 2402 mg/day at Days 7, 14, and 21, respectively. Patients were assessed on the Young Mania Rating Scale (YMRS; score ranges from 0-60), an augmented Brief Psychiatric Rating Scale (BPRS-A), and the Global Assessment Scale (GAS). Baseline scores and change from baseline in the Week 3 endpoint (last-observation-carried-forward[LOCF]) analysis were as follows:
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Valproate was statistically significantly superior to placebo on all three measures of outcome.
(2) Study 2: The second study enrolled adult patients who met Research Diagnostic Criteria for manic disorder and who were hospitalized for acute mania. Valproate was initiated at a dose of 250 mg TID and adjusted within a dose range of 750-2500 mg/day to achieve serum valproate concentrations in a range of 40-150 mcg/mL. Mean valproate doses for completers in this study were 1116, 1683, and 2006 mg/day at Days 7, 14, and 21, respectively. Study 2 also included a lithium group for which lithium doses for completers were 1312, 1869, and 1984 mg/day at Days 7, 14, and 21, respectively. Patients were assessed on the Manic Rating Scale (MRS; score ranges from 11-63), and the primary outcome measures were the total MRS score, and scores for 2 subscales of the MRS, i.e., the Manic Syndrome Scale (MSS) and the Behavior and Ideation Scale (BIS). Baseline scores and change from baseline in the Week 3 endpoint (LOCF) analysis were as follows:
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Valproate was statistically significantly superior to placebo on all three measures of outcome. An exploratory analysis for age and gender effects on outcome did not suggest any differential responsiveness on the basis of age or gender.
A comparison of the percentage of patients showing ≥ 30% reduction in the symptom score from baseline in each treatment group, separated by study, is shown in Figure 1.
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14.2 Epilepsy
The efficacy of valproate in reducing the incidence of complex partial seizures (CPS) that occur in isolation or in association with other seizure types was established in 2 controlled trials.
In one, multiclinic, placebo-controlled study employing an add-on design, (adjunctive therapy) 144 patients who continued to suffer 8 or more CPS per 8 weeks during an 8-week period of monotherapy with doses of either carbamazepine or phenytoin sufficient to assure plasma concentrations within the "therapeutic range" were randomized to receive, in addition to their original antiepilepsy drug (AED), either valproate or placebo. Randomized patients were to be followed for a total of 16 weeks. The following Table presents the findings.
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Figure 2 presents the proportion of patients (X axis) whose percentage reduction from baseline in complex partial seizure rates was at least as great as that indicated on the Y axis in the adjunctive therapy study. A positive percent reduction indicates an improvement (i.e., a decrease in seizure frequency), while a negative percent reduction indicates worsening. Thus, in a display of this type, the curve for an effective treatment is shifted to the left of the curve for placebo. This Figure shows that the proportion of patients achieving any particular level of improvement was consistently higher for valproate than for placebo. For example, 45% of patients treated with valproate had a ≥ 50% reduction in complex partial seizure rate compared to 23% of patients treated with placebo.
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The second study assessed the capacity of valproate to reduce the incidence of CPS when administered as the sole AED. The study compared the incidence of CPS among patients randomized to either a high- or low-dose treatment arm. Patients qualified for entry into the randomized comparison phase of this study only if 1) they continued to experience 2 or more CPS per 4 weeks during an 8- to 12- week-long period of monotherapy with adequate doses of an AED (i.e., phenytoin, carbamazepine, phenobarbital, or primidone) and 2) they made a successful transition over a 2-week interval to valproate. Patients entering the randomized phase were then brought to their assigned target dose, gradually tapered off their concomitant AED and followed for an interval as long as 22 weeks. Less than 50% of the patients randomized, however, completed the study. In patients converted to valproate monotherapy, the mean total valproate concentrations during monotherapy were 71 and 123 mcg/mL in the low-dose and high-dose groups, respectively.
The following Table presents the findings for all patients randomized who had at least one post-randomization assessment.
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Figure 3 presents the proportion of patients (X axis) whose percentage reduction from baseline in complex partial seizure rates was at least as great as that indicated on the Y axis in the monotherapy study. A positive percent reduction indicates an improvement (i.e., a decrease in seizure frequency), while a negative percent reduction indicates worsening. Thus, in a display of this type, the curve for a more effective treatment is shifted to the left of the curve for a less effective treatment. This Figure shows that the proportion of patients achieving any particular level of reduction was consistently higher for high-dose valproate than for low dose valproate. For example, when switching from carbamazepine, phenytoin, phenobarbital or primidone monotherapy to high-dose valproate monotherapy, 63% of patients experienced no change or a reduction in complex partial seizure rates compared to 54% of patients receiving low-dose valproate.
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14.3 Migraine
The results of 2 multicenter, randomized, double-blind, placebo-controlled clinical trials established the effectiveness of valproate in the prophylactic treatment of migraine headache.
Both studies employed essentially identical designs and recruited patients with a history of migraine with or without aura (of at least 6 months in duration) who were experiencing at least 2 migraine headaches a month during the 3 months prior to enrollment. Patients with cluster headaches were excluded. Women of childbearing potential were excluded entirely from one study, but were permitted in the other if they were deemed to be practicing an effective method of contraception.
In each study following a 4-week single-blind placebo baseline period, patients were randomized, under double blind conditions, to Valproate or placebo for a 12-week treatment phase, comprised of a 4-week dose titration period followed by an 8-week maintenance period. Treatment outcome was assessed on the basis of 4-week migraine headache rates during the treatment phase.
In the first study, a total of 107 patients (24 M, 83 F), ranging in age from 26 to 73 were randomized 2:1, valproate to placebo. Ninety patients completed the 8-week maintenance period. Drug dose titration, using 250-mg tablets, was individualized at the investigator’s discretion. Adjustments were guided by actual/sham trough total serum valproate levels in order to maintain the study blind. In patients on valproate doses ranged from 500 to 2500 mg a day. Doses over 500 mg were given in 3 divided doses (TID). The mean dose during the treatment phase was 1087 mg/day resulting in a mean trough total valproate level of 72.5 mcg/mL, with a range of 31 to 133 mcg/mL.
The mean 4-week migraine headache rate during the treatment phase was 5.7 in the placebo group compared to 3.5 in the valproate group (see Figure 2). These rates were significantly different.
In the second study, a total of 176 patients (19 males and 157 females), ranging in age from 17 to 76 years, were randomized equally to one of three valproate dose groups (500, 1000, or 1500 mg/day) or placebo. The treatments were given in 2 divided doses (BID). One hundred thirty-seven patients completed the 8-week maintenance period. Efficacy was to be determined by a comparison of the 4-week migraine headache rate in the combined 1000/1500 mg/day group and placebo group.
The initial dose was 250 mg daily. The regimen was advanced by 250 mg every 4 days (8 days for 500 mg/day group), until the randomized dose was achieved. The mean trough total valproate levels during the treatment phase were 39.6, 62.5, and 72.5 mcg/mL in the valproate 500, 1000, and 1500 mg/day groups, respectively.
The mean 4-week migraine headache rates during the treatment phase, adjusted for differences in baseline rates, were 4.5 in the placebo group, compared to 3.3, 3.0, and 3.3 in the valproate 500, 1000, and 1500 mg/day groups, respectively, based on intent-to-treat results (see Figure 4). Migraine headache rates in the combined valproate 1000/1500 mg group were significantly lower than in the placebo group.[1]
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References
Adapted from the FDA Package Insert.