Comparative effects of pinacidil and prazosin on blood pressure, weight, plasma volume, the renin-angiotensin-aldosterone system, and the renal kallikrein-kinin system in patients with essential hypertension.

Patients with essential hypertension were randomized to treatment with either prazosin or pinacidil, a new direct-acting vasodilator. Factors that might modulate the antihypertensive response and result in pseudotolerance to these drugs were measured before initiation of therapy and following 12 weeks of treatment. Despite significant reductions in blood pressure, pinacidil and prazosin did not produce an increase in plasma volume, did not activate the renin-angiotensin-aldosterone system, and did not interfere with the renal kallikrein-kinin system. The data fail to reveal evidence of physiologic compensatory changes that would lead to the development of pseudotolerance.