Wiktionary
dihydroergotamine
n. (context chemistry English) An ergot alkaloid used to treat migraines, believed to act upon serotonin receptors.
Wikipedia
Dihydroergotamine
Dihydroergotamine ( ; brand names D.H.E. 45 and Migranal) is an ergot alkaloid used to treat migraines. It is a derivative of ergotamine. It is administered as a nasal spray or injection and has an efficacy similar to that of sumatriptan. Nausea is a common side effect.
It has similar actions to the triptans, acting as an agonist to the serotonin 5-HT(1D) receptors and causing vasoconstriction of the intracranial blood vessels, but also interacts centrally with dopamine and adrenergic receptors. It can be used to treat acute intractable headache or withdrawal from analgesics.