The purpose of this study is to evaluate the safety and efficacy of three doses of topiramate (50 milligrams[mg], 100mg, and 200mg per day) compared with placebo in the prevention of migraine. The study will also assess the dose response relationship and the efficacy of treatment with topiramate versus placebo on Health-Related Quality of Life.

This is a randomized, double-blind, placebo-controlled, parallel-group, multi-center study to evaluate the efficacy and safety of three different doses of topiramate (50mg, 100mg, and 200mg daily) in migraine prophylaxis. The study consists of five phases: Baseline (determination of whether patients meet the eligibility criteria and tapering of any migraine medication patients are already taking), Double-Blind (patients receive either 50 milligrams[mg], 100mg, 200mg of topiramate, or placebo), Blinded Transition Phase (doses of study medication are adjusted over 7 weeks in preparation for the Open-Label Extension Phase), Open-Label Extension Phase (patients continue the study medication in open-label manner for up to 6 months; doses are adjusted to maximize effectiveness and minimize side effects), Taper/Exit Phase (study medication is slowly discontinued over 2 weeks). The primary study hypothesis is that one or more of the three doses of topiramate (50, 100, 200 mg/day) will be superior to placebo in the prophylaxis of migraine based on the change in monthly (28 day) migraine period rate from the Prospective Baseline Period to the Double-Blind Phase. Topiramate tablets (50milligrams [mg], 100mg, 200mg, or placebo) taken by mouth as twice-daily regimen during the 26-week Double-Blind Phase. Doses are adjusted and continued during the 6 month Open-Label Extension Phase after which they are tapered over 2 weeks.

Inclusion Criteria:

• Medical history consistent with migraine with or without aura according to the International Headache Society (IHS) for at least 6 months prior to the study
• Between 3 to 12 migraine periods and no greater than 15 headache days (migraine and non-migraine) per month during the Baseline Phase
• No clinically significant abnormalities on neurological exams, electrocardiogram (ECG) or clinical laboratory test results at baseline
• Female patients must be postmenopausal for at least 1 year, surgically incapable of childbearing, practicing abstinence, or practicing an acceptable method of contraception (requires negative pregnancy test)

Exclusion Criteria:

• Patients with headaches other than migraine
• Patients with episodic tension or sinus headaches
• Onset of migraine after age of 50 years
• Patients who have failed more than two adequate regimens for migraine prophylaxis
• Patients who overuse pain medications or certain other medications