Detection of sulfur dioxide in bronchodilator aerosols

Several bronchodilator drugs commonly used in respiratory therapy contain sodium metabisulfite as an antioxidant preservative. When aerosolized, these agents may release the irritant gas SO2 as a result of bisulfite decomposition. We found that agents that contain bisulfites generated SO2 concentrations of 2.0 ppm and greater, while bronchodilator solutions without bisulfite did not. Such levels are known to induce or to exacerbate asthmatic symptoms. Levels of SO2 were higher when solutions were nebulized with compressed air from a tank or electric compressor than when they were nebulized from a hand-bulb nebulizer. No significant lot-to-lot variations were found in the solutions tested.