Ineffectiveness of beta-adrenergic blockers on ventilatory response to carbon dioxide

The effects of the beta-adrenoceptor blockers atenolol, metoprolol, pindolol, and propranolol on the ventilatory response to carbon dioxide rebreathing have been determined in a double-blind randomized manner. Eight healthy, male, nonsmoking subjects received cumulative doses of each drug over a 10-hr period. The effects of each drug on heart rate and carbon dioxide sensitivity were determined at intervals of 2 hr and were related to plasma concentrations of each drug. Maximum reduction of exercise heart rate was achieved with all four beta blockers and plasma concentrations were in the usual therapeutic range for these drugs. There was considerable intersubject and within-subject variability in ventilatory responsiveness to inhaled carbon dioxide, but we were not able to discern any alteration in central sensitivity to increasing carbon dioxide concentrations.