 This Phase IIIb, open label, multi-centre study evaluated the safety and tolerability of frovatriptan taken by patients for up to 12 perimenstrual periods PMPs for the prevention of menstrual migraine MM. The study required approximately 300 patients to treat 6 PMPs and 100 patients to treat 12 PMPs. To achieve these numbers, 550 patients were to be enrolled into the study. Once enrolled, patients were requested to treat at least 6 PMPs in the first 9 months and 12 PMPs overall. Patients were to remain in the study for a maximum of 15 months or until they had completed the treatment of 12 PMPs, whichever occurred sooner.Patients were to take a loading dose of frovatriptan 5 mg two tablets twice daily on Day 1, followed by frovatriptan 2.5 mg twice daily on Days 2-6. 