Sumatriptan is used in Acute migraine headache. It relieves the symptoms of migraine and prevents the attack from becoming worse.How Sumatriptan works Migraine headaches are thought to result from the dilatation (swelling) of blood vessels in the head. Sumatriptan works by constricting (narrowing) the blood vessels in the head, stops transmission of pain signals to the brain, and blocks the release of chemicals that cause nausea and other migraine symptoms. This relieves the migraine attack.