EFFECTS OF EXERCISE TESTING, TRAINING AND BETA BLOCKADE ON SERUM POTASSIUM IN NORMAL SUBJECTS

To evaluate the effects of exercise testing, training and β blockade on serum potassium, 40 normal subjects (24 men, 16 women, mean age 33 years) had 4 maximal exercise tests with venipuncture for serum potassium before and ≤40 seconds after each test. After initial exercise testing, they were randomized to atenolol 50 mg daily, atenolol 100 mg daily, propranolol 80 mg twice daily or placebo. All began a 9-week dynamic exercise program for 8 weeks followed by a 1-week drug-free washout period. Tests were done after weeks 1, 8 and 9. A significant mean increase (p < 0.05) in serum potassium occurred with maximal exercise in the atenolol 50 mg and propranolol groups after 1 week of treatment (mean ± standard deviation, 4.78 ± 0.29 to 5.09 ± 0.43 mEq/liter and 4.81 ± 0.55 to 5.30 ± 0.33 mEq/liter). By week 8 after training, all β blockade groups showed an increase in postmaximal exercise test serum potassium (atenolol 50 mg, 4.78 ± 0.29 to 5.11 ± 0.26 mEq/ liter; atenolol 100 mg, 4.95 ± 0.41 to 5.16 ± 0.36 mEq/liter; propranolol, 4.81 ± 0.55 to 5.05 ± 0.29 mEq/liter). After washout, only the placebo group showed an increase in postmaximal test serum potassium (4.99 ± 0.46 to 5.35 ± 0.27 mEq/liter). Data indicate that hyperkalemia with maximal exercise testing increases after training with atenolol and propranolol compared to placebo and that this effect resolves once treatment is discontinued. © 1990.