Irritation/numbness/tingling of the nose/throat or a bad taste in the mouth may occur with the nasal spray form of this drug. Flushing, sensations of tingling/numbness/prickling/heat, weakness, drowsiness, or dizziness may also occur. If any of these effects persist or worsen, notify your doctor or pharmacist promptly. Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. Chest/jaw/neck tightness can commonly occur shortly after using sumatriptan. Only rarely are these signs of a serious condition. However, you may not be able to tell it apart from a serious reaction related to a lack of blood flow to the heart, brain or other parts of the body. Seek immediate medical attention if any of these unlikely but very serious (rarely fatal) side effects occur: chest pain, jaw/left arm pain, fainting, fast/irregular/pounding heartbeat, vision changes, weakness on one side of the body, confusion, slurred speech, sudden or severe stomach/abdominal pain, bloody diarrhea. Tell your doctor immediately if any of these unlikely but serious side effects occur: blue fingers/toes/nails, cold sensation of hands/feet, hearing changes, mental/mood changes, seizures. This medication may rarely cause a very serious condition called serotonin syndrome. The risk increases when this medication is taken with certain other drugs such as other "triptans" used to treat migraine headaches (e.g., rizatriptan, zolmitriptan), certain antidepressants including SSRIs (e.g., citalopram, fluoxetine, paroxetine) and NSRIs (e.g., duloxetine, venlafaxine), or a certain drug to treat obesity (sibutramine). Before taking this drug, tell your doctor if you take any of these medications. Serotonin syndrome may be more likely when you start or increase the dose of any of these medications. Seek immediate medical attention if you develop some of the following symptoms: hallucinations, unusual restlessness, loss of coordination, fast heartbeat, severe dizziness, high fever, severe nausea/vomiting/diarrhea, twitchy muscles. A serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction include: rash, itching/swelling (especially of the face/tongue/throat), dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.