Purpose: To evaluate the efficacy and safety of topiramate (TPM) as add-on therapy in medically intractable partial epilepsies.
Methods: We used a multicenter double-blind placebo-controlled randomized parallel-group trial consisting of 12 weeks of baseline phase, 10 weeks of titration phase, and 8 weeks of stabilization phase. The primary efficacy variable was the median seizure frequency reduction rate (MSFRR), and the other efficacy variables included responder rate, seizure-free rate, and global evaluations by the patient and the physician. The patient should have partial epilepsies refractory to the maximally tolerable doses of one to two antiepileptic drugs (AEDs) and should have two or more episodes of clinical seizures every 4 weeks during the baseline phase. The target dose of study drugs was 600 mg/day. The study drugs were started at the initial dose of 50 mg/day and gradually increased to the target dose over a 10-week period.
Results: A total of 177 patients was randomized into the TPM group (n = 91) and the placebo (PLC) group (n = 86). Baseline median seizure frequencies were 5.6 episodes/4 weeks in the TPM and the PLC groups. Among those who were randomized, 174 patients (TPM, 89 patients; PLC, 85 patients) were available for the efficacy measurement by intention-to-treat analysis. The MSFRR was 51.3% for TPM and 9.1% for PLC, which was highly in favor of TPM (p = 0.0001). The responder rate was 50.6% for TPM and 12.9% for PLC (p = 0.001). Seven (7.9%) of 89 patients taking TPM became seizure free compared with one (1.2%) of 85 patients taking PLC (p = 0.004). The global evaluation greatly favored TPM (p = 0.001). The incidence of adverse events (AEs) was higher in the TPM (81.3%) than in the PLC (48.9%) group, with central nervous system (CNS)-related AEs being the most frequent. Among individual AEs, anorexia (20.9%) and abdominal pain or discomfort (20.9%) were the most common AEs in the TPM group. AEs precipitated early drop-out in seven (7.6%) patients taking TPM and three (3.5%) patients taking PLC. No serious systemic AEs were observed.
Conclusions: TPM was highly effective and safe as add-on therapy in medically intractable partial epilepsies. Slower titration of TPM might be responsible for the lesser drop-out rate than previous trials, but the incidence of AEs was still high. The AE profile of TPM in Koreans was different from that in whites.