Effect of doxazosin or atenolol on exercise performance in physically active, hypertensive men

The effects of doxazosin or atenolol on exercise capacity in 15 male distance runners (mean age +/- SD 43 +/- 10 years) were compared in a double-blind, crossover study. Subjects performed a maximal treadmill test and a timed 2-mile run before and after each drug treatment. Cardiac output was determined by acetylene rebreathing at rest and at 30%, 50%, and 75% of maximal oxygen consumption. Oxygen consumption was determined at the above-mentioned workloads and at maximal effort. Both drugs were titrated to produce similar reductions in blood pressure and the final doses of atenolol and doxazosin were 43 +/- 22 and 6 +/- 6 mg, respectively. Atenolol reduced cardiac output (p < 0.05) and heart rate (p < 0.001) at rest and at all exercise intensities compared with the prior placebo phase, whereas doxazosin increased cardiac output at rest and at 50% effort (p < 0.05). Consequently, cardiac output was higher (p < 0.01) with doxazosin than with atenolol at rest and at 30% and 50% effort. Heart rate was higher with doxazosin (p < 0.01) during all exercise workloads. Despite these changes in cardiovascular function, there were no significant differences between the effect of the 2 study drugs on maximal oxygen consumption or 2-mile run times. We conclude that atenolol decreases rest and exercise heart rate and cardiac output compared with doxazosin, but that at modest doses neither drug adversely affects exercise performance in male hypertensive runners.