Central ventilatory depression by oral propranolol

Propranolol, 20 mg, was given orally four times daily for 5 days and placebo four times daily for 5 days in a randomized, double-blind fashion to nine healthy subjects. At the beginning of the study and on the last day of each medication pulse rate, blood pressure, airways resistance, maximum expiratory flow versus volume (using air and using 80% helium and 20% oxygen), spirometry before and after inhaled isoproterenol, and ventilatory and occlusion pressure responses to rebreathing carbon dioxide were measured. Results were compared by the Wilcoxon signed-rank test. Propranolol was associated with decreases in pulse rate (P = 0.002), systolic blood pressure (P = 0.024), and diastolic blood pressure (P = 0.027). There were no differences in airway resistance or the change of expiratory flow with helium-oxygen. Propranolol did not alter the preisoproterenol spirometry values but did reduce the response to isoproterenol. There were decreases in ventilatory responses (P = 0.004) and occlusion pressure responses (P = 0.006) at an end-tidal carbon dioxide of 60 mm Hg. Propranolol's beta-adrenergic blockade suppresses central ventilatory response to carbon dioxide.