A long-term clinical trial of prazosin.

The efficacy of prazosin given either alone or in combination with polythiazide was assessed in a study of 50 outpatients with essential hypertension. Among the 29 who completed 42 months of therapy, blood pressure fell significantly in 76%. Of the 21 who dropped out of the study after 1 to 41 1/2 months, 43% showed improvement, 38% showed no change, and 19% showed worsening of hypertension. The most common side effects were lack of energy and weakness. Diabetics and alcoholics tolerated prazosin well. Of the 50 patients who started treatment with prazosin alone, only 23 required addition of polythiazide.