Relative activities of atenolol and metoprolol on the cardiovascular system of man.

The effects or oral atenolol (100 mg once/day) and metoprolol (100 mg once/day, 100 mg twice/day and 300 mg once/day) have been compared with placebo on the heart rate and systolic blood pressure responses to exercise in 5 healthy volunteers. The drugs were given for 5 days in a double blind randomised fashion with each volunteer receiving each dose of drug. Measurements were made after the first dose on day 1 and after 5 days of dosing. The results on both heart rate and systolic blood pressure showed that overall (over a 24 h period) after acute (day 1) or after chronic (5 days) dosing, atenolol 100 mg once/day, metoprolol 100 mg twice/day and 300 mg once/day, were equivalent as beta-adrenoceptor blocking doses. Thus milligram for milligram atenolol and metoprolol do not produce equivalent blockade on the cardiovascular system of man.