• Changes from baseline to final visit in the Young Mania Rating Scale total score. Safety evaluations (incidence of adverse events, physical exams, vital signs, clinical laboratory tests including thyroid function tests) throughout the study.
  

• Changes from baseline to final visit in the Clinical Global Impressions Scale, Global Assessment Scale, Brief Psychiatric Rating Scale, and Montgomery-Asberg Depression Rating Scale. Rate of discontinuation due to efficacy failure.
  

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.