Imitrex^® (sumatriptan succinate) is a prescription drug used for the treatment of migraine headaches once they start. The drug is not effective at preventing migraines. Imitrex works by narrowing blood vessels in the head that become dilated during a migraine. You should take Imitrex as soon as possible once a migraine starts. Some of the conditions you should let your healthcare provider know about before you take Imitrex include high blood pressure; a history of seizures; and heart problems of any kind, especially a history of heart disease, angina, an irregular heart rhythm, or a heart attack.