The antihypertensive action of several beta-adrenoreceptor-blocking drugs.

The antihypertensive and pulse-slowing effects of racemic propranolol, oxprenolol, pindolol, practolol and d-propranolol were assessed in 54 hypertensive patients. Drug dosage was selected to be proportionate to beta-adrenoreceptor-blocking potency; d-propranolol dosage equalled approximately that of racemic propranolol. D-propranolol had onlyslight antihypertensive effect; the four other drugs were found to have a considerable and approximately equal antihypertensive effect. The degree of slowing of heart rate varied with the different drugs, being greatest with racemic propanolol. The effect on pulse rate did not correlate with the effect on blood pressure for most of the drugs. The falls in blood pressure induced by racemic propanolol were strongly correlated with those induced by each of the other drugs. The small falls in blood pressured induced by d-propranolol correlated also with those induced by practolol (which had no membrane activity) and are presumably due to its weak beta-adrenoreceptor-blocking action. The beta-adrenoreceptor-blocking action per se is responsible for the antihypertensive action of these drugs.