THE CARDIO-CIRCULATORY EFFECTS IN MAN OF NEO-SYNEPHRIN (1-α-hydroxy-β-methylamino-3-hydroxy-ethylbenzene hydrochloride) 1

Abstract

The threshold dosage of neo-synephrin in the avg. adult is about 2 mg. subcut., not quite 0.4 mg. intraven. and 50 mg. orally. The avg. dosage of neo-synephrin for satisfactory pressor and cardiac effect is about 5 mg. subcut., 0.8 mg. intravenously, or 250 mg. orally. With these dosages the pulse rate declines 15-35 beats per min., the systolic blood pressure rises 15 to 40 mm. and the diastolic blood pressure rises 10 to 30 mm. With rare exceptions, no sensations or symptoms other than pilo-motor excitation are elicited. Cardiac irregularities, extra systoles and escape phenomena do not occur with ordinary dosages. Neo-synephrin produces an increase in the size of the heart in both diastole and systole. The stroke output of the heart is increased but the min. output is generally decreased. There is a slight prolongation of circulation time and a slight increase in venous pressure. In the atropinized subject the pressor effect is augmented and tachycardia is produced. The same result is obtained in vagotomized animals and in the isolated or denervated heart. Tachycardia of sinus origin is readily controlled with neo-synephrin. It differs from epinephrine in its smaller pressor and cardiac potency, its longer duration of action, and in its stimulatory effect on some of the parasympathetic effectors, notably those of the cardiac vagus.