Long-term treatment of essential hypertension with guanfacine: Effect on cardiovascular complications, renin and prolactin

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Abstract
The effect of long-term treatment with guanfacine on blood pressure, heart rate, plasma renin activity (PRA) and prolactin was studied in 45 patients with mild to moderate hypertension over a period of 3years. An average daily dose of 2.8 mg guanfacine produced satisfactory control of blood pressure and there was a significant reduction in mean arterial pressure in all cases. During the first year of treatment, tolerance of guanfacine developed in 30 (67%) patients but this was significantly lower in the second and third years and was successfully overcome with the addition of chlorthalidone (50 mg/day) to the treatment regimen for 1 month. No correlation was demonstrated between the reduction in blood pressure and the effect of guanfacine on PRA and prolactin levels. Prolactin decreased significantly after 3 months of treatment while a late inhibition in PRA levels was observed. However, guanfacine inhibited early in treatment the diuretic-induced renin increase. The incidence of cardiovascular complications during the course of treatment with guanfacine (I case of stroke: 2.2% of patients) was compared to that in a non-treated group during 3 years of observation (17 patients: 5 cardiovascular accidents: 29% of patients). The development of cardiovascular accidents was associated with an increase in PRA and prolactin levels.