Hypersensitivity. Acute MI, hypotension. HTN, heart disease, hyperthyroidism, chronic right ventricular disease, CHF, liver/renal disease, peptic ulcer. Severe arrhythmias & seizure. Concomitant use w/ erythromycin, troleandomycin, lincomycin, allopurinol, cimetidine, propranolol, & antiflu vaccine. Phenytoin, other anticonvulsants & smoking. Lactation. Elderly.