Prazosin-induced bradycardia in acute treatment of hypertension

To the Editor. —Prazosin hydrochloride is a quinazolone derivative that has been shown to lower the BP by exerting a vasodilator effect on the resistance and capacitance vessels, resuiting from selective neuromuscular postsynaptic α-blockade. 1 A notable peculiarity of therapy with this drug is the absence of reflex tachycardia, which is commonly encountered with the use of other peripheral vasodilators. 1 A direct negative chronotropic effect of prazosin has been previously reported in experimental animals 2,3 and in one clinical study of patients with severe heart failure. 4 The occurrence of a negative chronotropic effect of prazosin during the short-term treatment of hypertension has been overlooked. We recently used 2 mg of oral prazosin hydrochloride to achieve a rapid BP reduction in a group of 17 consecutively seen patients who had been referred to the emergency room for severe hypertension. Within three hours, concomitant to the drop in BP, 13 patients