We investigated the ability of a calcium channel blocker nifedipine, given as an aerosol, to attenuate bronchoconstriction induced by citric acid, Ascaris antigen, and methacholine in Basenji-Greyhound dogs. citric acid 10% increased pulmonary resistance (RL) 4.2-fold +/- 1.0 (mean +/- SEM) and 1.7-fold +/- 0.7 in untreated and nifedipine-pretreated dogs (P less than 0.05). Dynamic compliance (Cdyn) fell to 0.58 +/- 0.07 and 0.66 +/- 0.07 of control values in untreated and nifedipine-treated dogs, respectively (p greater than 0.05). Ascaris antigen increased RL 5.1-fold +/- 0.83 and 3-fold +/- 0.48 in untreated and nifedipine-treated dogs, respectively (p less than 0.05); Cdyn decreased to 0.33 +/- 0.04 and 0.48 +/- 0.03 in untreated and nifedipine-treated dogs, respectively (p less than 0.05). In 5 dogs challenged with 0.3 mg/ml methacholine, RL increased 6.1-fold +/- 0.7 and 4.4-fold +/- 1.0 in untreated and nifedipine-treated dogs, respectively (p less than 0.05); Cdyn fell to 0.41 +/- 0.-3 and 0.46 +/- 0.07 of control values in untreated and nifedipine-treated dogs (P greater than 0.05). Neither 40% ethanol nor nifedipine-ethanol altered resting RL and Cdyn. We conclude that nifedipine effectively attenuates bronchoconstriction induced by citric acid, Ascaris antigen, and methacholine in dogs with hyperreactive airways.
Aerosols Airway Resistance