A Drug Interaction Study of the Pharmacokinetics of Topiramate and FLUNARIZINE When Given Together or Separately

This is a multicenter, randomized open-label study to be conducted in 2 groups of subjects. Group 1 will consist of migraine patients to be recruited at multiple sites and Group 2 will include healthy subjects at a single study center. In Group 1 a total of 36 subjects will be enrolled with a target of having 24 subjects complete the study. In Group 2, a total of 28 healthy subjects will be enrolled so that at least 24 will complete the trial. Group 1 will include patients under treatment for migraine prophylaxis with any dose of flunarizine for at least 4 weeks prior to the 6-week run-in phase. Once selected, patients will enter a 6-week run-in phase in which they will receive 5mg of flunarizine every evening. Following this run-in phase, patients will continue on flunarizine and be randomized into 2 subgroups of equal size; Subgroup 1a will consist of patients being treated with topiramate and flunarizine and Subgroup 1b, the control group, where patients will only be receiving flunarizine treatment. Patients in Group 1 (Subgroups 1a and 1b) will commence initial confinement (Day 1) after completing the 6-week run-in phase. All these patients must have a history of migraine according to IHS1 criteria for at least 1 year prior to study entry. For both Groups 1 and 2 dropouts will be replaced to ensure the required number of patients/subjects of each sex to complete the study. Safety will be assessed by studying the incidence and severity of treatment-emergent adverse events and abnormal findings of other safety evaluations. Changes in clinical laboratory test and vital sign results from Baseline to End of Study or early termination will be evaluated. In Group 1: 5 mg flunarizine every 24 hours (at 8:00 p.m.), beginning on Day -42 for 6 weeks, through Day -1. Patients will continue to receive this dose from Days 1 through 81. Group 1a: On Day 4 Topiramate dose titrated from 25 mg BID to 75 mg (25 mg am and 50 mg pm) by Day 19 and 50 mg BID by Day 26 - Day 81. Group 1b continue on Flunarizine only. Group 2: Topiramate beginning Day 2 titration from 25 mg BID to 50 mg BID by Day 5 through 18. 5mg Flunarizine daily starting Day 12- Day 18.