PROTECTIVE EFFECTS OF INHALED AMINOPHYLLINE ON METHACHOLINE-INDUCED AIRWAY RESPONSES IN GREYHOUND DOGS

Aminophylline can be delivered as a heated aerosol via an air-powered small-volume nebulizer, We tested the hypothesis that inhaled aminophy lline could attenuate the effects of inhaled methacholine on the airwa ys. Five greyhound dogs were anesthetized, intubated, and ventilated. An esophageal balloon and flow transducer were placed in the ventilato r circuit and connected to a BICORE CP-100 respiratory monitor. We mea sured mean lung resistance, lung dynamic compliance, and work of breat hing. Each dog was pretreated for 30 minutes with three different form ulations given randomly on separate days: aerosolized saline and intra venous saline, aerosolized aminophylline and intravenous saline, and a erosolized saline and intravenous aminophylline. The dogs were then ex posed to a series of five inhalations of methacholine of increasing co ncentrations given at 15-minute intervals, The results demonstrated a significant reduction in the work of breathing and lung resistance and significantly increased compliance after treatment with aerosolized a minophylline but not with intravenous aminophylline. These findings su pport our hypothesis that aerosolized aminophylline has a protective e ffect against methacholine-induced bronchospasm. The results further s uggest the possible use of aerosolized aminophylline for the treatment of obstructive lung disease.