Exercise metabolism in healthy volunteers taking atenolol, high and low doses of metoprolol CR/Z0K, and placebo.

1. Exercise and beta-adrenoceptor blockade have important roles in the prevention and treatment of cardiovascular disease, but fatigue and a reduced capacity to exercise are commonly reported side effects of beta-adrenoceptor blockers. The reduced capacity to exercise may be partly caused by a reduction in fat metabolism. 2. We investigated the effects of atenolol 50 mg, metoprolol CR/Z0K 50 mg, metoprolol CR/Z0K 100 mg and placebo, on heart rate, energy expenditure, fat oxidation, plasma free fatty acids, glycerol, glucose, lactate, ammonia and perceived exertion during 2 h of treadmill walking at 40% of maximal oxygen uptake in 20 healthy volunteers. 3. Compared with placebo (38.0%), total fat oxidation was significantly lower on atenolol 50 mg (30.1%) and metoprolol CR/Z0K 100 mg (31.0%), but not on metoprolol CR/Z0K 50 mg (33.7%). Reductions in fat oxidation correlated well (r2 = 0.970) with reductions in exercising heart rate, and probably reflected the degree of beta 1-adrenoceptor blockade. Maximum plasma ammonia concentration was reached after 45 min of exercise on atenolol, 60 min on metoprolol CR/Z0K 100, and 75 min on metoprolol CR/Z0K 50, and was higher than placebo on all active drug treatments. 4. The greater reduction in fat oxidation with atenolol may be a reflection of a peak in plasma concentration, which is avoided with a controlled release preparation.

RCT Entities:   Population Interventions Outcomes