Effect of guanfacine on blood pressure and renin activity in hypertensive patients.

1. The effect of treatment with guanfacine for 12 weeks on blood pressure and plasma renin activity was investigated in 24 hypertensive patients (WHO I-III). 2. Systolic, diastolic and mean blood pressure values underwent significant reductions with a constant dose of guanfacine 3 mg daily for 1 week: from 197/115/149 (systolic/diastolic/mean) mmHg before therapy to 166/97/126 mmHg. After 4 weeks of treatment at varying doses, the blood pressure decreased to 157/91/118 mmHg, and after 12 weeks of treatment it levelled off at 147/83/109 mmHg. Heart rate remained essentially unchanged throughout the observation period. 3. During exercise, blood pressure and heart rate increased to the same extent during therapy as before treatment. Orthostatic hypotension was not seen in any of the patients. 4. Renin values decreased under therapy from 3.3 to 2.3 ng ml-1 h-1, but at no time during treatment did this decrease correlate with that of blood pressure. 5. Guanfacine treatment was accompanied by relatively few and mild side-effects.