Ergotamine, sold under the brand name Ergomar among others, is an ergopeptine and part of the ergot family of alkaloids; it is structurally and biochemically closely related to ergoline.

[14] It's also contraindicated if patient is taking macrolide antibiotics (e.g., erythromycin), certain HIV protease inhibitors (e.g., ritonavir, nelfinavir, indinavir), certain azole antifungals (e.g., ketoconazole, itraconazole, voriconazole) delavirdine, efavirenz, or a 5-HT1 receptor agonist (e.g., sumatriptan).

At higher doses, it can cause raised arterial blood pressure, vasoconstriction (including coronary vasospasm) and bradycardia or tachycardia.

[22][23] Ergotamine is a secondary metabolite (natural product) and the principal alkaloid produced by the ergot fungus, Claviceps purpurea, and related fungi in the family Clavicipitaceae.

These precursor compounds are the substrates for the enzyme, tryptophan dimethylallyltransferase, catalyzing the first step in ergot alkaloid biosynthesis, i.e., the prenylation of L-tryptophan.

Enzyme-catalyzed or spontaneous cyclizations, oxygenations/oxidations, and isomerizations at selected residues precede, and give rise to, formation of ergotamine.