Amidephrine-II: Cardiovascular actions of a new sympathomimetic amine

Abstract Amidephrine mesylate, a new potent sympathomimetic amine, was compared with phenylephrine using several cardiovascular preparations. The vasopressor molar potency (amidephrine: phenylephrine) was as follows: anesthetized dogs (i.v.) 1:·9; anesthitized cats (i.v.) 1:2·1; unanesthetized rats (i.p.) 5·7:1; unanesthetized rats (p.o.) 3·7:1. The duration of action in each case was longer than phenylephrine. No tolerance to the pressor action was observed in monkeys which had received the drug daily for 6 months prior to blood pressure reactivity studies. Amidephrine induced reflex bradycardia in dogs and rats. This was abolished by atropine sulfate or bilateral vagotomy. Amidephrine elicited only minor alterations in heart rate, myocardial contractile force and coronary flow in the isolated rabbit heart preparation. Intranasal pressure was reduced in anesthetized dogs by the intravenous administration of doses of amidephrine which did not alter systemic arterial blood pressure. No evidence of after-congestion was observed. Phenylephrine was 1·4 times more active than amidephrine in this preparation. Amidephrine administered directly into the artery increased femoral arteriolar and renal arteriolar resistance. In the femoral arterial bed of the dog, phenylephrine was 1·4 times more active than amidephrine as a vasoconstrictor while in renal studies amidephrine was 2·5 times more active than the hydroxyl analogue.