Sumatriptan

Sumatriptan is the first triptan, a serotonin 5-HT1B/1D receptor agonist used for acute treatment of migraine with or without aura and for cluster headache. It is available as tablets, nasal spray and subcutaneous injection, and the injection is the fastest. It must not be used in people with vascular disease.

Mechanism. Constricts cranial blood vessels and inhibits release of calcitonin gene-related peptide and other neuropeptides from trigeminal nerve endings.

Pharmacokinetics. Oral bioavailability is about 14%, intranasal about 17% and subcutaneous about 97%. Half-life is about 2 hours. It is metabolised by monoamine oxidase A, with kidney excretion of metabolites.

First-line use. Acute migraine attacks, taken early in the headache phase.

• Oral sumatriptan: 50 mg at onset (100 mg in some people). If migraine returns after an initial response, repeat after at least 2 hours. Do not repeat for the same attack if there was no response to the first dose. Maximum 300 mg in 24 hours in most labels (200 mg in some).

• Combination with naproxen 500 mg taken together gives better relief than either alone.

• Intranasal: 10 to 20 mg once, repeated after at least 2 hours. Maximum 40 mg in 24 hours.

• Subcutaneous: 6 mg once, repeated after at least 1 hour if migraine recurs. Maximum 12 mg in 24 hours.

Specialist use. Cluster headache: subcutaneous 6 mg at onset, up to two injections in 24 hours separated by at least 1 hour, or intranasal 20 mg. Adolescents 12 to 17 years use intranasal 10 mg under specialist advice.

Kidney, liver, weight and age.

• Kidney: no adjustment.

• Liver: mild to moderate impairment, maximum oral dose 50 mg; severe impairment, contraindicated.

• Older adults: not studied over age 65, so avoid.

Contraindications. Ischaemic heart disease, previous myocardial infarction, coronary vasospasm, peripheral vascular disease, previous stroke or transient ischaemic attack, uncontrolled hypertension, hemiplegic or basilar migraine, severe hepatic impairment, monoamine oxidase A inhibitors within 2 weeks, and ergotamine or another triptan within 24 hours.

Serious adverse effects. Myocardial infarction, coronary vasospasm, arrhythmia, stroke, serotonin syndrome, ischaemic colitis, seizures, and medication overuse headache.

Common adverse effects. Chest, throat or neck tightness, tingling, flushing, dizziness, fatigue and nausea.

Interactions. Monoamine oxidase A inhibitors, ergot alkaloids and other triptans are contraindicated. Selective serotonin reuptake inhibitors, serotonin and noradrenaline reuptake inhibitors and St John's wort add serotonin syndrome risk.

Common prescribing errors. Prescribing to people with unrecognised vascular risk. Use on more than 10 days each month. Repeating doses when there was no response. Giving within 24 hours of another triptan.

Special groups.

• Pregnancy: more data than for other triptans; use if clearly needed.

• Breastfeeding: infant exposure is low and use is usually acceptable; some labels advise waiting 12 hours after a dose.

• Cardiovascular risk: assess risk factors before the first dose, and give the first dose under supervision if risk is high.

Formulations. Tablets 25, 50 and 100 mg. Nasal spray 10 and 20 mg. Subcutaneous injection 6 mg in 0.5 mL. Swallow tablets with water, at the first signs of headache.

Monitoring.

• Baseline blood pressure and cardiovascular risk review.

• Headache diary of attack frequency and acute treatment days, with treatment limited to under 10 days each month.

Stopping. No taper is needed. Stop for chest pain or neurological symptoms.

Referral and escalation. Refer for more than two attacks each week, suspected medication overuse headache, aura lasting over 1 hour, or new severe headache with neurological signs.