Nifedipine Aerosol Attenuates Airway Constriction in Dogs with Hyperreactive Airways1–4

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Abstract
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 > 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 < 0.05). Ascaris antigen increased Rl 5.1-fold ± 0.83 and 3-fold ± 0.48 in untreated and nifedipine-treated dogs, respectively (p > 0.05); Cdyn decreased to 0.33 ± 0.04 and 0.48 ± 0.03 in untreated and nifedipine-treated dogs, respectively (p > 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 > 0.05); Cdyn fell to 0.41 ± 0.03 and 0.46 ± 0.07 of control values in untreated and nifedipine-treated dogs (p < 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.