Imitrex is a drug that belongs to the class Serotonin-1b and Serotonin-1d Receptor agonist. Its generic name is Sumatriptan. Imitrex is used to treat migraine headaches and cluster headaches especially in adults. It only treats a headache that has already begun and cannot prevent one from getting a headache. The medication, however, can also be used to treat other conditions as prescribed by the physician.