1. Clinical Overview
Sumatriptan is a selective serotonin (5-HT1B/1D) receptor agonist, classified as a triptan. It is a first-line abortive therapy for acute migraine attacks with or without aura, and for the acute treatment of cluster headache episodes. 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 (oral); 10 minutes (subcutaneous); 15 minutes (intranasal) | Up to 24 hours for migraine relief; 2-4 hours for cluster headache | Approximately 15% (oral); 96% (subcutaneous) |
2. Mechanism of Action
Sumatriptan binds with high affinity to serotonin 5-HT1B and 5-HT1D receptors. Activation of 5-HT1B receptors on intracranial blood vessels (including those in the dura mater) leads to vasoconstriction, reversing the vasodilation associated with migraine. Activation of 5-HT1D receptors on sensory nerve endings of the trigeminal system inhibits the release of pro-inflammatory neuropeptides (e.g., CGRP, substance P), thereby reducing neurogenic inflammation and pain signal transmission to the brainstem.
3. Indications & Uses
- Acute treatment of migraine attacks with or without aura
- Acute treatment of cluster headache episodes (typically subcutaneous form)
4. Dosage & Administration
Adult Dosage: For Migraine: 50mg or 100mg tablet taken as a single dose at the onset of headache. If headache recurs, a second dose may be taken after at least 2 hours. Maximum: 300mg in 24 hours. For Cluster Headache (SC route typical): 6mg injection. Oral 100mg may be used off-label but is less effective.
Administration: Tablet to be swallowed whole with a glass of water. Can be taken with or without food, although food may delay absorption slightly. Do not crush or chew. A second dose should not be taken for the same attack if the first dose provided no relief. The minimum interval between two doses is 2 hours.
5. Side Effects
Common side effects may include:
- Sensation of warmth/hot flushes
- Tingling/paraesthesia
- Heaviness/pressure sensation (chest, throat, limbs)
- Dizziness/vertigo
- Fatigue/drowsiness
- Nausea/vomiting
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Monoamine Oxidase-A Inhibitors (Moclobemide, Clorgyline) | Markedly increased sumatriptan plasma levels and risk of serotonin syndrome. Contraindicated. | High |
| Selective Serotonin Reuptake Inhibitors (SSRIs: Fluoxetine, Sertraline, Escitalopram) & SNRIs (Venlafaxine, Duloxetine) | Increased risk of serotonin syndrome (weakness, hyperreflexia, incoordination). Monitor closely. | Moderate |
| Ergot Alkaloids (Ergotamine, Dihydroergotamine, Methysergide) | Prolonged vasospastic reactions. Contraindicated within 24 hours of each other. | High |
| Other Triptans (Rizatriptan, Zolmitriptan, Eletriptan) | Additive vasoconstrictive effects. Contraindicated within 24 hours of each other. | High |
| Methylergometrine (Methylergonovine) | Increased risk of vasospasm. Avoid concomitant use. | High |
| St. John's Wort | Potential increased risk of serotonin syndrome. | Moderate |
| Propranolol | Increases sumatriptan plasma concentration by ~50%. Consider a lower sumatriptan dose (e.g., 50mg). | Moderate |
| Cimetidine | Slight increase in sumatriptan AUC. Clinical significance minimal. | Low |
7. Patient Counselling
- DO take at the first sign of a migraine headache.
- DO NOT use for more than 10 headache days per month to avoid Medication Overuse Headache (MOH).
- DO NOT take a second dose for the same attack if the first dose fails.
- DO wait at least 2 hours between doses if a recurrent headache occurs.
- DO NOT take if you have taken another triptan or ergotamine medication in the last 24 hours.
- DO inform your doctor about all other medications, especially SSRIs/SNRIs and MAO inhibitors.
- DO seek immediate medical attention if you experience chest pain, shortness of breath, sudden severe headache, or neurological symptoms.
8. Toxicology & Storage
Overdose: Symptoms may include hypertension, cardiovascular collapse, tremor, seizures, paralysis, cyanosis, bradycardia, reflex tachycardia, 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. Do not use after the expiry date printed on the pack.