Hypotensive and cardiovascular action of budralazine in unanesthetized and unrestrained dogs

In renal hypertensive dogs, 1-[2-(1,3-dimethyl-2-butenylidene)hydrazino]phthalazine (budralazine) at doses of 1 and 2.5 mg/kg p.o. produced a gradual, progressive and significant fall in blood pressure which reached a maximum 3--4 h after dosing and persisted for 6--10 h. The hypotensive response to 1 mg/kg p.o. of budralazine was almost comparable to that to 2.5 mg/kg p.o. of reference drug hydralazine, but the duration of action of the former was much longer than that of the latter. At equihypotensive doses, budralazine was found to be approximately 3 times less potent than hydralazine in producing tachycardia. In normotensive dogs, budralazine at a dose of 1 mg/kg p.o. produced a significant increase in renal blood flow and a tendency for the increase in coronary blood flow associated with a significant and non-significant decrease in the peripheral vascular resistance. At this dose level, blood pressure remained almost unchanged.