ACUTE HEMODYNAMIC EFFECTS OF METHOXAMINE IN MAN

The circulatory effects of single intravenous injections of 0. 065 mg. /kg. methoxamine were investigated in 5 healthy volunteer subjects. Ninety minutes after the first injection, atropine 1-2 mg was adminis- tered intravenously and the injection of methoxamine repeated. Cardio-vascular parameters were evaluated by ballistocardiographic and dye-dilution methods, the former data continuously calculated by an analog computer. Methoxamine briefly, but markedly, depressed heart rate, cardiac output, and left ventricular work. Stroke volume decreased moderately, while mean arterial pressure increased moderately, and total peripheral resistance increased markedly. A preliminary partial vagal block with atropine permitted a greater increase in mean arterial pressure, withlesser changes in all other parameters except stroke volume, thus making methoxamine a "better" vasopressor. It is sug-gested that some of the depressant effects of methoxamine are related to intense arteriolar constriction, venous pooling of blood, reflex vagal depression of the atria and ventricles, and direct beta-adrenergic blocking, and excitation-contraction uncoupling actions.