Comparison of antihypertensive activity of atenolol and methyldopa at rest and during exercise

In a double-blind, cross-over trial, 37 hypertensive patients were treated in random order, after a 4-week run-in period, with 100 mg atenolol in a single daily dose, or 250 mg methyldopa three times daily (or 500 mg three times daily in case of poor response). Both therapeutic regimens significantly reduced blood pressure (13/13 mmHg for atenolol and 17/10 mmHg for methyldopa) in an erect position. The higher dose of methyldopa gave a further significant reduction only for the systolic standing blood pressure. No statistical difference was found between the antihypertensive activity of the two drugs, but atenolol reduced heart rate more than did methyldopa. Side effects occurred more frequently during methyldopa administration and most often during the first days of treatment. During exercise (treadmill test) the two drugs induced the same antihypertensive response, but atenolol provoked a greater reduction of exercise tachycardia. Whereas total oxygen consumption was not affected by the two drugs, atenolol induced a much greater reduction of the myocardial oxygen consumption evaluated by the product of the systolic blood pressure X heart rate. These findings show that atenolol at the 100-mg daily dose is as effective as the full dosage of methyldopa and in addition shows better tolerance, a simpler therapeutic scheme, and less incidence of side effects.