Small open-label and controlled trials suggest that the antiepileptic drug topiramate is effective for migraine prevention. To assess the efficacy and safety of topiramate for migraine prevention in a large controlled trial. A 26-week, randomized, double-blind, placebo-controlled study was conducted during outpatient treatment at 52 North American clinical centers. Patients were aged 12 to 65 years and had a 6-month history of migraine (International Headache Society criteria) and 3 to 12 migraines a month but no more than 15 headache days a month during a 28-day prospective baseline phase. After a washout period, patients meeting entry criteria were randomized to topiramate (50, 100, or 200 mg/d) or placebo. Topiramate was titrated by 25 mg/wk for 8 weeks to the assigned or maximum tolerated dose, whichever was less. Patients continued receiving that dose for 18 weeks. The primary efficacy measure was change from baseline in mean monthly migraine frequency. Secondary efficacy measures included responder rate (proportion of patients with > or =50% reduction in monthly migraine frequency), reductions in mean number of monthly migraine days, severity, duration, and days a month requiring rescue medication, and adverse events. The month of onset of preventive treatment action was assessed. Of 483 patients randomized, 468 provided at least 1 postbaseline efficacy assessment and comprised the intent-to-treat population. Mean monthly migraine frequency decreased significantly for patients receiving topiramate at 100 mg/d (-2.1, P =.008) and topiramate at 200 mg/d (-2.4, P<.001) vs placebo (-1.1). Statistically significant reductions (P<.05) occurred within the first month with topiramate at 100 and 200 mg/d. The responder rate was significantly greater with topiramate at 50 mg/d (39%, P =.01), 100 mg/d (49%, P<.001), and 200 mg/d (47%, P<.001) vs placebo (23%). Reductions in migraine days were significant for the 100-mg/d (P =.003) and 200-mg/d (P<.001) topiramate groups. Rescue medication use was reduced in the 100-mg/d (P =.01) and 200-mg/d (P =.005) topiramate groups. Adverse events resulting in discontinuation in the topiramate groups included paresthesia, fatigue, and nausea. Topiramate showed significant efficacy in migraine prevention within the first month of treatment, an effect maintained for the duration of the double-blind phase.
