Comparative antihypertensive effects of guanabenz and clonidine

The safety and efficacy of guanabenz and clonidine were compared in 188 hypertensive patients during a 6-month double-blind trial. Mean supine diastolic blood pressure (SDBP) decreased from 103 to 88 mm Hg (p less than 0.01) among guanabenz patients and from 101 to 88 mm Hg (p less than 0.01) among clonidine patients who completed 6 months of b.i.d. therapy. Clinically significant individual SDBP decreases occurred in 85% of the guanabenz patients and 83% of the clonidine patients after 6 months. Adverse effects, consisting primarily of drowsiness, dry mouth, dizziness, and weakness, were similar in the two therapy groups. The responses obtained with guanabenz (b.i.d.) were maintained, along with a decrease in adverse effects, by an equivalent single daily dose of guanabenz during a second 6 months of therapy. Seventy-six per cent (13/17) of the patients whose blood pressure was not adequately controlled by guanabenz alone after 8 weeks of therapy subsequently responded to a combination of guanabenz and hydrochlorothiazide. Similarly, 85% (17/20) of the patients who failed to respond to clonidine alone subsequently responded to guanabenz either alone or in combination with hydrochlorothiazide. These results suggest that guanabenz or the combination of guanabenz and hydrochlorothiazide is effective therapy for the majority of hypertensive patients.