Acute transient SO2-induced airway hyperreactivity: effects of nedocromil sodium

The effect of nedocromil sodium given as an aerosol on the immediate lung hyperreactivity and lung inflammation caused by a 2-h exposure to 400 ppm SO2 has been studied in dogs. Exposure to SO2 caused an immediate increase in bronchial responsiveness to histamine aerosol that lasted for approximately 2 h. The total number of cells recovered by bronchial lavage increased postexposure. Initially this increase was caused by epithelial cells (0.25 and 1 h) and later by neutrophils (1, 2, 3, and 4 h). There was no significant change in the numbers of lymphocytes, macrophages, eosinophils, goblet cells, or mast cells in the lavages. Nedocromil sodium (approximately 8 mg) given as a nebulized aerosol before and after SO2 exposure prevented the increase in lung reactivity and attenuated the increase in the total number of cells (epithelial cells and neutrophils) in the lung lavages for the 4 h after exposure. Nedocromil sodium did not affect the reactivity of normal dogs to histamine aerosol. Nedocromil sodium appears to act as an anti-inflammatory agent in this model of lung inflammation, preventing an increase in lung reactivity and reducing cell infiltration. The mechanism of action of nedocromil sodium in this model is unknown.