Migraine patients treated with topiramate showed significant reductions in migraine frequency compared with those receiving placebo, according to the findings of a 26-week outpatient study conducted in 52 North American clinical centres.

"Treatment with topiramate at doses of 100 to 200 mg/d was associated with significant improvements during the entire double-blind treatment phase for several other migraine efficacy measures, including migraine days per month and acute rescue medication days per month, and demonstrated a significantly higher responder rate than placebo," writes Jan Lewis Brandes, MD, Nashville Neuroscience Group, Tennessee, United States, and colleagues for the MIGR-002 Study Group.

The patient population consisted of individuals, with a 6-month history of migraine by International Headache Society criteria and aged between 12 and 65 years, who experienced 3 to 12 migraines per month but no more than 15 headache days per month during a 28-day prospective baseline phase. The placebo group consisted of 114 patients, while 117 patients received 50 mg/d topiramate, 120 received 100 mg/d topiramate, and 117 received 200 mg/d topiramate. The groups were balanced in baseline clinical and demographic characteristics, and 87% of the patients were women.

Baseline mean monthly migraine frequency was 5.4, 5.8, and 5.1, respectively in the 50 mg, 100 mg, and 200 mg topiramate groups and 5.6 in the placebo group compared with 4.1, 3.5, and 3.0, respectively in the 50 mg, 100 mg, and 200 mg topiramate groups and 4.5 in the placebo group during the double-blind phase of the study. This change from baseline was statistically significant in the 100 mg and 200 mg topiramate groups but not in the 50 mg topiramate group compared with placebo.

Overall, 39%, 49%, and 47% of patients in the 50 mg, 100 mg, and 200 mg topiramate groups, respectively, compared with 23% of the placebo group achieved a 50% reduction in monthly migraine frequency. Topiramate treatment was also associated with larger reductions in the mean monthly number of migraine days and the mean monthly number of rescue medication days compared with placebo.

Adverse events that led to discontinuation included paraesthesia and fatigue, both in 8%; diarrhoea, hypaesthesia, and memory difficulties in 3% each; and confusion in 4% of the 100 mg topiramate group. All other events that led to discontinuation had an incidence of 2% or less and most adverse events were mild to moderate. Also, topiramate treated patients showed dose-dependent weight loss while placebo treated patients showed weight gain.