<prompt> Which of the following drug reduces blood pressure primarily by directly decreasing heart rate alone?PropranololPrazosinAlpha methyl dopaNitroprusside sodium  <response>: Ans. A PropranololRef: Katzung 10e p165, 169; KDT 8the p158Methyldopa is useful in the treatment of mild to moderately severe hypertension. It lowers blood pressure chiefly by reducing peripheral vascular resistance, with a variable reduction in heart rate and cardiac output.Prazosin and nitroprusside are vasodilators and produce reflex tachycardia instead of causing bradycardia.Propranolol is a non selective beta blocker and acts mainly by decreasing heart rate. 