ergot alkaloid, one of a large group of alkaloids derived from a common fungus, Claviceps purpurea. The alkaloids comprise three groups: the amino acid alkaloids typified by ergotamine, the dihydrogenated amino acid alkaloids such as dihydroergotamine, and the amine alkaloids such as ergonovine. ▪ INDICATIONS: Ergotamine and dihydroergotamine are less effective oxytocics than ergonovine. Therefore ergonovine, given orally or intravenously, is currently used in obstetrics to treat or prevent postpartum uterine atony and to complete an incomplete or missed abortion. Ergotamine is prescribed to relieve migraine headache. It acts by reducing the amplitude of arterial pulsations in the external carotid branches of the cranial arteries resulting from stimulation of vasoconstrictive alpha receptors, and it may also act as a serotonin antagonist. ▪ CONTRAINDICATIONS: Peripheral vascular disease, coronary artery disease, hypertension, renal or hepatic dysfunction, and sepsis are contraindications for ergot alkaloids. Pregnancy prohibits their use because they may cause contractions of the uterus, decreased blood flow to the fetus, and fetal death. ▪ ADVERSE EFFECTS: Ergot poisoning may result from prolonged or excessive use of the drug or accidental ingestion of contaminated grain. Signs of toxicity are thirst, diarrhea, dizziness, chest pain, abnormal and variable rate of cardiac contraction, nausea and vomiting, digital paresthesia, severe cramping, and seizures. Tissue anoxia and gangrene of the extremities may occur as a result of prolonged vasoconstriction if poisoning is severe.
