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 animals2,3 and in one clinical study of patients with severe heart failure.4The 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
Kobrin I, Stessman J, Yagil Y, Ben-Ishay D. Prazosin-Induced Bradycardia in Acute Treatment of Hypertension. Arch Intern Med. 1983;143(10):2019-2023. doi:10.1001/archinte.1983.00350100203049