SMOKING, BETA BLOKERS, AND METHYLSERGIDE & SUMATRIPTAN INCREASES RISK OF VASCULAR OCCULSION DUE TO PERIPHERAL VASOCONSTRICTION. SIMULTANEOUS USE OF ORAL CONTRACEPTIVES INCREASE RISK OF THROMBOSIS. ERYTHROMYCIN & HIV PROTEASE INHIBITORS LIKE INDINAVIR, NELFINAVIR, AMPRENAVIR, RITONAVIR, SAQUINAVIR INCREASES PLASMA CONCENTRATION OF ERGOTAMINE. HALOTHANE DIMINISH THE EFFECTS OF ERGOTAMINE ON UTERUS. VASOCONSTRICTOR EFFECTS OF ERGOTAMINE ARE POTENTIATED BY SYMPATHOMIMETICS. ERGOTAMINE SHOULD NOT BE GIVEN UNTIL AT LEAST 6 HRS AFTER STOPPING A SEROTONIN AGONIST( 5-HT1) LIKE SUMATRIPTAN SINCE THERE IS AN ADDITIONAL RISK OF PROLONGED VASOSPASM SOMETIMES LEADING TO GANGRENE OF PERIPHERAL PARTS. CONVERSLY A DELAY IS ADVISED BEFORE STARTING A SEROTONIN AGONIST IN PATIENTS WHO HAVE BEEN RECCIEVING ERGOTAMINE ; SUMATRIPTAN SHOULD NOT BE GIVEN UNTIL AT LEAST 24 HRS AFTER STOPPING THE ERGOTAMINE PREPARATION. GLYCERYL TRINITRATE INCREASE THE ORAL BIOAVAILABILITY & PLASMA CONCENTRATION OF DIHYDROERGOTAMINE. ERGOTAMINE MAY INHIBIT THE METABOLISM OF TACROLIMUS. ARTERIAL OCCLUSION HAS BEEN REPORTED IN PATIENTS TAKING METHYSERGIDE AND HIGH DOSES OF ERGOTAMINE.