Comparison of the effects of labetalol and propranolol in healthy men at rest and during exercise.

1. Oral labeltalol and propranolol have been compared in healthy men with regard to the effects on heart rate, blood pressure and peak expiratory flow rate (PEFR) at rest and the changes induced by exercise. 2. Labetalol caused a dose-related reduction in standing diastolic pressure at rest whereas propranolol did not but neither drug altered standing systolic pressure at rest. 3. In the doses compared, propranolol was consistently more potent than labetalol in influencing blood pressure changes induced by exercise, in lowering heart rate at rest and reducing PEFR at rest. 4. Labetalol and propranolol are both beta-adrenoreceptor antagonists and the observed differences in the profiles of the two drugs are probably directly related to the additional alpha-adrenoreceptor blocking property of labetalol not possessed by propranolol. Because of these differences labetalol may be expected to have advantages in the treatment of hypertension.