Comparison of the effects of atenolol and propranolol in labile hypertension.

The effects of a single daily dose of 100 mg. of atenolol and an equivalent dose of propranolol were compared during a crossover, 15 day blind trial in a group of young labile hypertensives. Arterial pressure, heart rate, systolic time intervals and the carotid pulse upstroke time, recorded by external non-invasive procedures, were measured before and 4 and 8 hours after the last dose of both drugs. Both beta blocking agents significantly reduced and stabilized the arterial BP and the heart rate to normal values. However, a tendency to return to abnormal values was observed 8 hours after propranolol administration. Both drugs provoked an increase in the pre-ejection period, but with propranolol this increase was related to a larger isovolumetric contraction time, pointing to a negative inotropic action. The carotid pulse upstroke time was increased to normal values with atenolol. Propranolol failed to alter this value. Atenolol in a single oral daily dose is recommended in the treatment of labile hypertension.