Rizatriptan is a prescription only headache medication that narrows the blood vessels around the brain. Rizatriptan can reduce substances in the body that can trigger headache pain, sensitivity to sound and light, nausea and other migraine symptoms. Rizatriptan is used to treat migraine headaches. Rizatriptan will only treat an ongoing headache that has already started. It will not prevent headaches or reduce the number of attacks.