1. Clinical Overview
Sumatriptan is a selective serotonin (5-HT1B/1D) receptor agonist, commonly known as a 'triptan'. It is a first-line abortive therapy for the acute treatment of moderate to severe migraine attacks with or without aura, and for cluster headaches. It works by causing vasoconstriction of cranial blood vessels, inhibiting neurogenic inflammation, and blocking pain pathways in the trigeminal system.
| Onset | Duration | Bioavailability |
|---|---|---|
| 10-30 minutes after oral administration; peak plasma concentration in 2-4 hours. | Clinical relief typically lasts 2-4 hours, though the drug's effect on preventing headache recurrence can extend up to 24 hours. | Approximately 15% (oral), due to significant first-pass metabolism. |
2. Mechanism of Action
Sumatriptan binds with high affinity to vascular 5-HT1B receptors and neuronal 5-HT1D receptors. Activation of 5-HT1B receptors on dilated intracranial extracerebral blood vessels causes vasoconstriction, reversing the vasodilation associated with migraine. Activation of presynaptic 5-HT1D receptors inhibits the release of pro-inflammatory neuropeptides (like CGRP and substance P) from trigeminal sensory nerves, reducing neurogenic inflammation and pain signal transmission in the trigeminal-vascular system.
3. Indications & Uses
- Acute treatment of migraine attacks with or without aura in adults.
- Acute treatment of cluster headache episodes in adults (though subcutaneous injection is preferred for cluster headaches).
4. Dosage & Administration
Adult Dosage: For Migraine: A single 50mg tablet, taken with fluids at the onset of migraine pain. If headache recurs, a second dose may be taken after at least 2 hours. Maximum: 100mg in a 24-hour period. For Cluster Headache: Oral route is less effective; 50mg dose can be used, but max 100mg/24h.
Administration: Swallow tablet whole with a glass of water. Can be taken with or without food. Do not crush or chew. Take at the earliest sign of migraine headache. If no response to the first dose, do not take a second dose for the same attack. Do not use for more than 10 headache days per month to avoid MOH.
5. Side Effects
Common side effects may include:
- Sensation of tingling, heat, heaviness, pressure, or tightness in any part of the body (including chest and throat).
- Flushing.
- Dizziness, vertigo.
- Fatigue, drowsiness.
- Nausea and vomiting.
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Monoamine Oxidase-A Inhibitors (e.g., Moclobemide, Clorgiline) | Markedly increased sumatriptan plasma levels (up to 7-fold). Increased risk of serotonin syndrome. | Contraindicated |
| Selective Serotonin Reuptake Inhibitors (SSRIs e.g., Sertraline, Escitalopram) / SNRIs (e.g., Venlafaxine) | Increased risk of serotonin syndrome (weakness, hyperreflexia, incoordination). | Major |
| Ergot Alkaloids (e.g., Ergotamine, Dihydroergotamine) | Prolonged vasospastic reactions. A 24-hour gap is mandatory between doses. | Contraindicated |
| Other Triptans (e.g., Rizatriptan, Zolmitriptan) | Additive vasoconstrictive effects. Risk of serotonin syndrome. | Contraindicated |
| 5-HT1 agonists (e.g., Buspirone) | Potential for additive serotonergic effects. | Moderate |
| St. John's Wort | Potential increased serotonergic effects. | Moderate |
| Propranolol | Increases sumatriptan plasma concentration by about 50%. | Moderate |
7. Patient Counselling
- DO take the tablet at the first sign of a migraine headache.
- DO take with a full glass of water.
- DO wait at least 2 hours before considering a second dose for the same attack, if needed.
- DO NOT take a second dose if the first dose provides no relief for that attack.
- DO NOT use for more than 10 days per month to prevent Medication Overuse Headache.
- DO NOT take if you have taken any ergotamine or another triptan in the last 24 hours.
- DO NOT crush or chew the tablet.
8. Toxicology & Storage
Overdose: Symptoms may include hypertension, cardiovascular collapse, tremor, seizures, paralysis, cyanosis, respiratory depression, and loss of consciousness. In animals, massive overdose led to convulsions, ataxia, and salivation.
Storage: Store below 30°C. Protect from light and moisture. Keep out of reach of children.