EFFECT OF DOXAZOSIN OR ATENOLOL ON EXERCISE PERFORMANCE IN PHYSICALLYACTIVE, HYPERTENSIVE MEN

The effects of doxazosin or atenolol on exercise capacity in 15 male d istance runners (mean age +/- SD 43 +/- 10 years) were compared in a d ouble-blind, crossover study, Subjects performed a maximal treadmill t est and a timed 2-mile run before end after each drug treatment, Cardi ac output was determined by acetylene rebreathing at rest and at 30%, 50%, and 75% of maximal oxygen consumption Oxygen consumption was dete rmined at the above-mentioned workloads and at maximal effort. Both dr ugs were titrated to produce similar reductions in blood pressure and the final doses of atenolol and doxazosin were 43 +/- 22 and 6 +/- 6 m g, respectively, Atenolol reduced cardiac output (p <0.05) and heart r ate (p <0.001) at rest and at all exercise intensities compared with t he prior placebo phase, whereas doxazosin increased cardiac output at rest and at 50% effort (p <0.05). Consequently, cardiac output was hig her (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 stu dy drugs on maximal oxygen consumption or 2-mile run times, We conclud e that atenolol decreases rest and exercise heart rate and cardiac out put compared with doxazosin, but that at modest doses neither drug adv ersely affects exercise performance in male hypertensive runners.