The effects of antianginal drugs on energy expenditure during exercise in normal subjects

The respiratory quotient (RQ = VCO2/VO2) provides important information (ie, the ratio of carbohydrate to fat utilization) concerning energy expenditure. We studied the effects of various antianginal drugs on energy expenditure during steady-state aerobic exercise in 9 healthy adult men. The drugs used were propranolol (a non-selective beta-blocker), metoprolol (a beta-1 selective blocker), amosulalol (an alpha- and beta-blocker), nicardipine (a calcium antagonist) and isosorbide dinitrate. Each drug was administered for 2 weeks, followed by a 2-week washout period. VO2, VCO2 and RQ were measured with an expired gas analyzer during treadmill exercise tests before and during the administration of each drug. Two protocols of constant-load exercise were performed: Protocol 1 lasted for 10 min at a speed of 5.5 km/h and a grade of 0%, (at a level of about 30% peak VO2), while Protocol 2 lasted for 10 min at a speed of 7 km/h and a grade of 0%, (at a level of about 40% peak VO2). RQ during exercise was significantly increased and VO2 was decreased after propranolol, metoprolol and amosulalol (P < 0.05). Neither nicardipine nor isosorbide dinitrate produced significant changes in these values. These data suggest that propranolol, metoprolol and amosulalol increase the efficiency of energy expenditure during ordinary physical activity by increasing the utilization of carbohydrate and by decreasing the utilization of fat.