The influence of beta-adrenoceptor antagonists with and without partial agonist activity on exercise tolerance and muscle lactate production.

Epanolol is a beta-adrenoceptor antagonist with partial agonist activity, a property which could be useful in reducing the fatigue associated with beta blockers. In a double-blind, randomized, crossover study we have investigated the effects of metoprolol 100 mg b.d., epanolol 100 mg b.d., and epanolol 200 mg b.d. on blood pressure, heart rate, and exercise-induced fatigue in 10 hypertensive men. Fatigue was measured subjectively by the Borg rating scale and objectively by blood lactate concentrations. Resting and exercise heart rates were lower with metoprolol than with either dose of epanolol. Preexercise standing diastolic blood pressure was lowered by metoprolol, but there were no other treatment effects on blood pressure. Exercise-induced fatigue was not altered by any treatment, whether measured subjectively or objectively. These results do not support the hypothesis that partial agonist activity improves exercise tolerance in hypertensive patients treated with beta-adrenoceptor antagonists.