Effect of guanabenz on blood pressure responses to posture and exercise.

A single dose of guanabenz was examined for effects upon blood pressure, heart rate, plasma catecholamines, and plasma renin activity in a randomized, double-blind, crossover design. Eight patients were studied when supine, standing, and during submaximal exercise. Guanabenz reduced blood pressure in subjects who were supine or standing. Heart rate was lowered only in the supine subjects. Guanabenz induced reduction in plasma catecholamines subjects in all positions and the reduction correlated with the placebo level for both norepinephrine and epinephrine. Plasma renin activity was not significantly affected by guanabenz. The results indicate that the central alpha-agonist action of guanabenz reduces sympathoadrenal function to a greater extent in hyperadrenergic hypertensive patients than in those without this disorder.