From the Guidelines
Sumatriptan is not a vasodilator, but rather a vasoconstrictor that works by binding to serotonin (5-HT1B/1D) receptors in cranial blood vessels, causing them to constrict. This mechanism of action is supported by studies on the management of migraine headaches, which highlight the efficacy of triptans, including sumatriptan, in relieving migraine pain 1. The vasoconstrictive properties of sumatriptan are also noted in guidelines on the management and prevention of migraines, which advise against the use of triptans in patients with uncontrolled hypertension or basilar or hemiplegic migraine 1.
Key points to consider when using sumatriptan include:
- Its efficacy in relieving migraine pain, with a clinical impression of effectiveness rated as 4 out of 4 1
- Its contraindications, including coronary artery disease, uncontrolled hypertension, and other cardiovascular conditions where vasoconstriction could be harmful 1
- Its potential side effects, such as nausea, warmth, vomiting, vertigo, and malaise 1
Overall, the use of sumatriptan as a vasoconstrictor for the treatment of migraine headaches is supported by the evidence, but its potential risks and contraindications must be carefully considered in clinical practice.
From the FDA Drug Label
Sumatriptan tablets may cause non-coronary vasospastic reactions, such as peripheral vascular ischemia, gastrointestinal vascular ischemia and infarction (presenting with abdominal pain and bloody diarrhea), splenic infarction, and Raynaud’s syndrome
- Vasospasm is a key concept here, which implies vasoconstriction, not vasodilation.
- The text does not mention vasodilation as an effect of sumatriptan.
- Instead, it highlights the risk of vasospastic reactions, which are associated with vasoconstriction. The FDA drug label does not support that sumatriptan is a vasodilator. In fact, it suggests the opposite: sumatriptan may cause vasoconstriction. 2
From the Research
Sumatriptan's Mechanism of Action
- Sumatriptan is a selective 5-hydroxytryptamine1d (5-HT1d)-receptor agonist, which has been shown to have a vasoconstrictor effect on certain intracranial blood vessels 3, 4, 5.
- The vasoconstrictor response of sumatriptan is reproducible outside the migraine attack, suggesting a direct vascular effect rather than an indirect neural mechanism 3.
- Sumatriptan has been found to constrict arterio-venous anastomoses that may be dilated during a migraine attack, which correlates with its antimigraine activity 3.
Effects on Cerebral and Ocular Hemodynamics
- Sumatriptan prevents the effect of nitroglycerin-induced vasodilation in the middle cerebral artery, but not in the ophthalmic artery, supporting the concept that sumatriptan directly vasoconstricts distended basal cerebral arteries 5.
- Sumatriptan has a small vasoconstrictor action on resistance vessels, as indicated by the measurement of ocular fundus pulsations 5.
- Transcranial Doppler studies have shown that sumatriptan increases flow velocity in the internal carotid artery and the middle cerebral artery on the headache side, but not in the external carotid and basilar arteries 6.
Vasopressor Response and Coronary Artery Vasoconstriction
- Sumatriptan causes a vasopressor response in the systemic and pulmonary arterial circulations, and coronary artery vasoconstriction, as demonstrated by digital subtraction angiography and invasive haemodynamic monitoring 7.
- The coronary artery vasoconstriction is significant, with a reduction in coronary artery diameter of 12.9 +/- 6.9% 7.