Effect of penbutolol and propranolol on normal airway response to salbutamol

The specific airway conductance (sGaw) response of eight normal men to inhaled salbutamol, 200, 600, and 1800 micrograms, was measured on 3 separate days. On each occasion subjects received either placebo, long-acting propranolol (160 mg), or penbutolol (40 mg) orally in a double-blind manner after baseline lung function determination. After placebo, mean sGaw rose from a baseline of 2.07 +/- 0.15 to 2.81 +/- 0.25 kPa-1 X sec-1 after 200 micrograms salbutamol. There was little further airway dilation with higher doses of salbutamol. With long-acting propranolol, there was no significant airway dilation after 200 micrograms salbutamol but there was after 600 and 1800 micrograms inhaled salbutamol; baseline sGaw rose from 2.02 +/- 0.17 to 2.70 +/- 0.28 and 2.95 +/- 0.32 kPa-1 X sec-1. Penbutolol prevented any significant airway dilation with all doses of salbutamol. Penbutolol at the doses used appears to be a more potent blocker of beta 2-receptors than does propranolol.