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Oxcarbazepine
 

Efficacy of oxcarbazepine

Monotherapy studies
Three international, randomized, double-blind, monotherapy trials of oxcarbazepine in patients with newly diagnosed or previously untreated partial-onset or primary generalized seizures have been performed. One study (Christe et al. 1997) compared oxcarbazepine to valproate, and the other two (Guerreiro et al.1997; Bill et al. 1997) compared oxcarbazepine to phenytoin—one in adults and one in children and adolescents. Blinded treatment was administered three times daily and titrated over 8 weeks based on clinical response. In the study of oxcarbazepine versus valproate, randomized patients were titrated to between 900 and 2,400 mg daily for both AEDs. In the other two studies, oxcarbazepine dosages were 450 to 2,400 mg daily and phenytoin dosages were 150 to 800 mg daily. Efficacy and tolerability were recorded during a 48-week maintenance period.

In each of these studies, the primary efficacy variable was the proportion of seizure-free patients who had at least one seizure assessment during the maintenance period. In the study comparing oxcarbazepine to valproate, slightly more than half of the patients in each treatment group remained seizure-free during the maintenance period; there was no statistically significant treatment difference. Similarly, there was no treatment difference in the percentage of patients with partial-onset seizures who were seizure-free (46% for oxcarbazepine and 48% for valproate) or the proportion of patients with primary generalized seizures who were seizure-free (72% for oxcarbazepine and 62% for valproate).

In the study testing oxcarbazepine versus phenytoin in adults, nearly 60% of patients in each treatment group were seizure-free during the maintenance period; there was no statistically significant treatment difference. Similarly, there was no treatment difference in the percentage of patients with partial-onset seizures who were seizure-free (56% with oxcarbazepine and 53% for phenytoin) or the proportion with primary generalized seizures who were seizure-free (64% with oxcarbazepine and 68% with phenytoin).

In the pediatric study of oxcarbazepine versus phenytoin, nearly 60% of the children in each treatment group were seizure-free during the maintenance period; there was no statistically significant difference in seizure frequency. Similarly, there was no treatment difference in the percentage of patients with partial-onset seizures who were seizure-free (60% for oxcarbazepine and 62% for phenytoin) or the proportion of patients with primary generalized seizures who were seizure-free (59% for oxcarbazepine and 54% for phenytoin).

An outpatient, double-blind oxcarbazepine monotherapy study compared seizure frequencies in patients maintained at oxcarbazepine 2,400 mg/day to seizure frequencies in patients taking tapering dosages down to 300 mg/day (Sachdeo et al. 2001). The primary efficacy measure, a survival analysis of the time to meet one of the exit criteria, was significantly in favor of the high-dose oxcarbazepine group.

Comparisons of oxcarbazepine and Tegretol (carbamazepine) have generally found them to be equally effective.

Adjunctive therapy studies
A summary of studies in which oxcarbazepine was used adjunctively for partial seizures reported that 41% of adults who took oxcarbazepine had their seizures reduced in frequency by at least half, compared to 13% of those who added a placebo to their previous medications (Cramer et al. 2001).

A comparable study of oxcarbazepine as adjunctive therapy for children also found that 41% of those who took oxcarbazepine had at least a 50% decrease in seizure frequency (Glauser et al. 2000). Of those who took a placebo, 22% had a similar reduction.

Reviewed by Steven C. Schachter, MD
Submitted: 01/03/08