[The antihypertensive response to prazosin, a selective vascular alpha blocker. A multicenter study].

The efficacy and safety of oral prazosin was assessed in 108 ambulatory mild (91-104 mmHg diastolic pressure) to moderate (104-114 mmHg) essential hypertensive patients. After a 2 week no-drug control period, prazosin, 2, 4, 8 or 10 mg per day was given in 2 weeks periods as needed to obtain control of blood pressure. A seating diastolic pressure of < or = 90 mmHg was defined as adequate response. Satisfactory blood pressure response was obtained in 86% of patients, with doses of 4 mg or less in 70%. Treatment results were not related to initial blood pressure level, but obese patients were more resistant to drug effect (p < 0.05). Heart rate and laboratory parameters did not change. Adverse effects, mainly headache, dizziness and palpitations, were noticed in 46 patients (43%) and occurred with the lower dose in 78% of them. Adverse effects were slight or moderated and lasted from 1 day to 2 weeks in most patients. Treatment was discontinued in 2 patients, one because of persistent dizziness which was promptly relieved after stopping the drug and another due to syncope occurring immediately after a dose increase. We conclude that oral prazosin at low doses is an effective and well-tolerated drug which should be considered in the treatment of mild to moderate hypertension.