Hemodynamic effects of oxdralazine and hydralazine in hypertension

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Abstract
Oxdralazine, a pyridazine that induces prolonged arteriolar dilation in animals, was given orally in doses of 15-30 mg to 7 [human] subjects with hypertension. Arterial pressure fell in 2 h (average mean of 16 mm Hg), peaking in 3-4 h and was sustained for more than 6 h. Cardiac output and heart rate rose in 2 h (2.1 l/min and 17 bpm [beats/min]) and were elevated at 6 h (3.1 l/min and 22 bpm). Pulmonary arterial pressure and pulmonary arteriolar resistance did not change. In 6 subjects receiving oxdralazine with hydralazine 50-75 mg at 1 wk intervals, hydralazine induced earlier, less sustained decreases in arterial pressure and systemic vascular resistance and less of a rise in heart rate than oxdralazcine alone. Circulating norepinephrine levels (radioenzymatic method) 3 h after oxdralazine rose from a mean of 159-294 pg/ml, a greater (P < 0.05) effect than after hydralazine. At the doses tested, oxdralazine is a potent systemic arteriolar dilator with longer-sustained action and more prominent reflex sympathetic stimulation than hydralazine.

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