The purpose of this study is to assess the efficacy and safety of adding topiramate as compared to placebo to the medications a patient with bipolar disorder is already taking (lithium or valproate) to see if adding topiramate will better control the patient's manic symptoms.

Many patients with bipolar disorder (manic-depressive illness) require more than one medication to control their symptoms. This is a 12-week, multicenter, randomized, double-blind, placebo-controlled, parallel-groupd study to evalute the efficacy and safety of topiramate versus placebo as add-on therapy to lithium or valproate for the treatment of bipolar 1 disorder as an outpatient setting. These patients must already be taking either lithium or valproate for at least 6 weeks before the first visit and have been on the same dose of the mood stabilizer for at least 2 weeks before the first visit. Paitents will be randomized to receive either placebo or topiramate, an anti-seizure medication not approved for the treatment of bipolar disorder, in addition to their lithium or valporate. The study consists of 56-day titration (topiramate will be titrated up to 400mg per day or the maximum tolerated dose), 28-day continuation period, and 7 days of follow-up to taper off the medication. The study hypothesis is that topiramate will be more effective than placebo in the treatment of mania in type 1 bipolar disorder patients as measured by the Young Mania Rating Scale (YMRS) and will be well tolerated. YMRS is a questionnaire consisting of 11 items designed to assess severity of mania symptoms.

Patients will start taking topiramate 25 mg per day or placebo by mouth. Over the next 8 weeks, doses will be increased to up to 400 mg per day or to the maximum tolerated dose, whichever is lower. After the first 8 weeks, patients will stay at the established dose for the next 4 weeks.

Inclusion Criteria:

• Confirmed diagnosis of Bipolar Disorder Type I
• Total Young Mania Rating Scale (YMRS) score of 18 or higher
• Currently being treated with a mood stabilizer (lithium or valproate)
• Having a stable therapeutic dose of the mood stabilizer in their bloodstream
• Currently not requiring hospitalization

Exclusion Criteria:

• Patients taking an antidepressant or anti-seizure medication
• Hospitalized paitents
• Women who are pregnant or breast-feeding
• Women who are not using birth control
• Patients with history of drug or alcohol abuse