ergot alkaloid

:  any of a group of alkaloids found in ergot or produced synthetically and that include the psychedelic drug LSD as well as numerous pharmacologically useful compounds (such as ergonovine and ergotamine) noted especially for their contractile effect on smooth muscle (as of the uterus or blood vessels) The vasoconstrictive properties of ergot alkaloids have made them useful in treating migraine headaches (ergotamine tartrate) and postpartum hemorrhage (methyl ergonovine).—Ruth A. Etzel, The Journal of the American Medical Association, 22/30 Jan. 2002—compare ergotism