Systemic and renal hemodynamic effects of trimazosin: a new vasodilator.

Trimazosin was administered for 2 days in doses-ranging from 50 to 200 mg to 16 patients with essential hypertension. The patients were randomized on the third day and received either the active drug in a single dose of 300 mg or a placebo. Systemic hemodynamic studies in both the supine and 50 degrees upright tilt position, including the Valsalva maneuver and a 1 min sustained handgrip test at 30% maximal voluntary contraction, were performed during control and 0, 1, 2, and 3 hr after drug administration. Renal function studies including plasma renin activity (PRA) were performed during control period and 3 hr after drug administration. Trimazosin reduced arterial pressure and peripheral vascular and renal vascular resistances, increased heart rate, cardiac output, and renal blood flow, and had no effect on glomerular filtration rate or PRA. Placebo had no effect on any of the above-mentioned parameters. The increase in renal blood flow was independent of cardiac output. We conclude that trimazosin lowers arterial pressure through a direct arteriolar dilation and reduction in peripheral vascular resistance. Its direct renal effects would make it a useful agent in the treatment of hypertension associated with renal function impairment.