Assessment of Metoprolol, a Cardioselective Beta-Blocking Agent, during Chronic Therapy in Patients with Angina Pectoris

Abstract

Ten patients with typical angina pectoris and without hypertension, congestive heart failure or other disease were treated with alternating four-week courses of metoprolol ( a β1 cardioselective beta-blocking agent), propranolol and placebo. Midway through each four-week period, drug dosage was doubled; thus, regimes were metoprolol, 150 and 300 mg/day, propranolol, 120 and 240 mg per day and placebo, 3 and 6 tablets per day. Serum concentrations of metoprolol increased with increasing dosage in a proportion very similar to that seen with propranolol. Statistically significant reductions in angina frequency/nitroglycerin consumption, and statistically significant increases in total work performed on a bicycle ergometer, were found with both active compounds when compared with placebo. No significant differences were noted between the two active compounds. Though most patients showed greatest improvement on the higher of the two drug dosages, three patients with metoprolol and two with propranolol responded best on the lower dose regime. Both compounds reduced heart rate at rest and during exercise. Neither reduced arterial pressure at rest, but both reduced arterial pressure during excercise. It is concluded that metoprolol is as effective as propranolol in the reduction of angina attacks and improvement in exercise tolerance during chronic therapy in patients with uncomplicated angina pectoris. It is now appropriate to study the effects of metoprolol in patients with coronary artery disease in whom the harmful effects of non-selective beta-blockade heretofore have precluded optimal therapy with beta-blocking drugs.