Serotonin Agonists

Serotonin agonists, also known as triptans, help relieve the manifestations of an existing migraine or cluster headache.

Prototype and Other Medications

Medication Classification – Serotonin Agonists

The prototype medication serotonin agonist that treats existing migraines and cluster headaches is sumatriptan. Other triptans in this category include zolmitriptan.

Expected Pharmacologic Action

As previously stated, serotonin agonists work by reversing the 5-HT/CGRP ratio. They do this by activating 5-HT receptors, which promote vasoconstriction and suppress the release of CGRP. This prevents the inflammatory response from occurring.

Adverse Drug Reactions

Adverse effects of serotonin agonists include chest pressure, or a feeling of “heaviness” in the chest, which may result from vasoconstriction of blood vessels in the lungs and the esophagus as well as bronchoconstriction. In some clients, vasospasm of the coronary vessels may also occur, causing anginal pain. Other common side effects include CNS effects such as tingling sensations and vertigo.

Interventions

Clients may report a feeling of heaviness when taking a serotonin agonist for a migraine headache. But reassure them that this is a common side effect. Due to the risk of vasospasm of the coronary arteries, monitor vital signs closely after the first dose.

Safety Alert

Clients who take a serotonin agonist may experience heaviness in the chest due to their vasoconstrictive properties. However, coronary vasospasm may also occur and cause anginal chest pain. Measure vital signs immediately for clients who develop chest pain and notify the provider due to the possibility of cardiac ischemia.

Administration

Administer serotonin agonists orally or by nasal spray. Sumatriptan is also available as a subcutaneous injection. When administering the medication by nasal spray, spray it once into a single nostril and repeat in 2 hours as needed. A single dose ranges from 5 to 20 mg, and the maximum daily dose is 40 mg. When administering the drug by subcutaneous injection, give it once and then repeat in 1 hour if there is no relief. Do not give more than two subcutaneous doses in a 24-hour period. When administering an oral tablet, give one oral tablet and repeat once after 2 hours if there’s no relief. A single oral dose can range from 25 to 100 mg. Do not give more than 200 mg in a 24-hour period.

Safety Alert

Do not exceed the maximum number of doses in a 24-hr period. Excessive vasoconstriction can occur, compromising blood flow to vital organs.

Client Instructions

When telling clients how to take serotonin agonists, be sure they understand the need to notify their provider at once for pressure or tightness in the chest or heaviness in the back, jaw, or throat that does not resolve spontaneously. And if CNS manifestations such as tingling and vertigo occur after taking the medication, they should report this to the provider during their next visit.

Contraindications and Precautions

The vasoconstriction that serotonin agonists cause can occur in other parts of the body. This means that clients who have a history of coronary artery disease, angina, or previous MI should avoid taking serotonin agonists. Peripheral vasoconstriction can also harm clients who have severe hypertension or peripheral vascular disease, or whose cerebral circulation is already compromised due to a cerebrovascular accident, or stroke. Use serotonin agonists with caution in clients who have liver or kidney insufficiency.

Safety Alert

Use of serotonin agonists by clients who have coronary artery disease, a history of angina or previous MI, severe hypertension, or peripheral vascular disease is contraindicated. Their vasoconstrictive effects can significantly compromise blood flow in the heart and peripheral vasculature, resulting in ischemia.

Interactions

Sumatriptan can interact with MAO inhibitors if clients take them within 2 weeks of each other, causing sumatriptan toxicity. The use of ergotamine or another triptan within 24 hours of sumatriptan also increases the risk of angina. Clients who take serotonin agonists for other disorders and then take sumatriptan to abort a migraine headache may experience serotonin syndrome. Finally, the herbal supplement St. John’s wort may cause sumatriptan toxicity.