Pathophysiology of propranolol in hypertension.

Only recently approved for use in the treatment of hypertension in the US, the beta-adrenergic receptor blocking compound propranolol has been used elsewhere for this purpose since 1964. The exact mechanisms to explain why and how "beta-blocking drugs" reduce arterial pressure are not known with certainty, but possible explanations include: (1) "resetting" of the baroreceptors, (2) reduction of cardiac output, (3) adaptation of circulation ("autoregulation"), (4) inhibition of renin release, (5) central nervous system effects, (6) possible antihypertensive metabolites, and (7) other unknown mechanisms or a combination of known mechanisms. Propranolol alone has been demonstrated to be extremely effective in reducing arterial pressure. In addition, the combination of propranolol and vasodilator and diuretic drugs would be expected to reduce vascular resistance without reflexive cardiac stimulation and with prevention of sodium and fluid retention.