The effects of oral propranolol and metoprolol on lung function and exercise performance in chronic airways obstruction.

Fifteen men with chronic airways obstruction received a test dose of propranol 20 mg orally. Six developed increased breathlessness. Nine who tolerated the test dose received metoprolol (100 mg) and propranolol (80 mg) on different days in a randomized double-blind fashion. Changes in resting and exercise heart rate, spirometry and exercise tolerance were measured 1 and 6 hours later. The drugs had similar effects on heart rate. Propranolol, but not metoprolol, caused significant reduction in forced expiratory volume in one second (FEV1) and peak expiratory flow rate. Neither drug produced significant changes in forced vital capacity (FVC) or exercise performances in the group as a whole, although the range of changes was wide. Despite considerable reduction in FEV1 and FVC in some individuals, most reported no increase in symptoms. Changes in exercise tolerance at 1 hour correlated significantly with changes in FVC but not with those in FEV1. It is proposed that changes in FEV1, though of pharmacological interest, may be less relevant clinically than changes in FVC.