Effects of prazosin on hemodynamics and sympatho-adrenal activity in hypertensive patients.

Summary We studied peripheral and central hemodynamics and plasma catecholamine levels in 12 previously untreated patients with essential hypertension before and during treatment with the α1-adrenoceptor antagonist prazosin (9.8 ±1.1 mg/day for 3–6 weeks following dose titration) as a single drug. Prazosin did not alter intra-arterially recorded blood pressures in the group as a whole, in spite of adequate plasma levels (12.6 ± 1.2 ng/ml). There were no changes in cardiac output, blood volume, systemic or forearm vascular resistance, or forearm venous tone at rest during treatment. The blood pressure response to prazosin was correlated to pretreatment systemic and forearm vascular resistances. Arterial adrenaline levels were unchanged, but noradrenaline levels increased from 1.30 ± 0.10 to 1.85 ± 0.20 nM (p