AbstractThe duration of the coronary artery vasoconstrictor effect of ergonovine maleate is an important clinical parameter that has not been clearly defined. Since ergonovine is generally administered in incremental, cumulative doses and since this agent may have potentially serious toxic effects related to its vasoconstrictor properties, knowledge of duration of this effect is crucial to its safe and efficacious use. We present clinical evidence of ergonovine‐induced coronary artery spasm recurring after pharmacologic relief of a first episode of ergonovine‐induced spasm. Recurrent spasm occurred 18 minutes after a cumulative dose of 0.15 mg ergonovine and 14 minutes after intravenous nitroglycerin was given to ameliorate the initial spasm. Therefore, clinical monitoring of patients after ergonovine administration should be designed to identify a possibly prolonged duration of vasoconstrictor effect of the drug. Sequential doses of ergonovine at intervals of ten minutes or less should be recognized as having cumulative effect. The duration of action of pharmacologic agents utilized to alleviate ergonovine‐induced coronary artery spasm should exceed the potential duration of action of ergonovine in order to minimize the possibility of late spasm.