Modulation of the effects of salbutamol by propranolol and atenolol

Six healthy volunteers were given single oral doses of 8 mg salbutamol, 40 mg propranolol, 100 mg atenolol, 8 mg salbutamol plus 40 mg propranolol and 8 mg salbutamol plus 100 mg atenolol, in a placebo controlled study. Plasma potassium fell following salbutamol and rose following atenolol or propranolol, and the hypokalaemic effect of salbutamol was reversed more effectively by propranolol than by atenolol. Although blood glucose rose after salbutamol, it was unaffected by any of the other treatments. Lying and standing pulse rate rose after salbutamol and fell equally after either beta-adrenoceptor antagonist, and fell more after salbutamol plus propranolol than after salbutamol plus atenolol. Blood pressure rose after salbutamol and fell after each of the other treatments. Forty milligrams propranolol was thus more effective than 100 mg atenolol in reversing the metabolic effects of 8 mg salbutamol, and was as effective in reversing the cardiovascular effects. In cases of symptomatic salbutamol overdose, propranolol should be considered as an antidote provided the patient is not asthmatic.