Dihydroergotamine

Dihydroergotamine is an ergot alkaloid derivative. Its actions involve multiple receptors. For example, it stimulates 5-HT1B receptors on the smooth muscle of cerebral blood vessels, especially in the intracranial and internal carotid arterial systems, causing vasoconstriction and reducing the vascular responses associated with vasodilation during migraine attacks. It also activates 5-HT1D receptors, thereby inhibiting the release of neuropeptides such as CGRP, substance P, and neurokinin A from trigeminal nerve endings. In addition, it has partial agonist activity at α1-adrenergic receptors, which contributes to vasoconstriction. It also has mild antagonistic activity at α2 receptors, which may increase sympathetic activity and slightly raise blood pressure. Dihydroergotamine also acts as a partial agonist at D2 dopamine receptors, which may cause side effects such as nausea and vomiting.