administration of retinoids by inhalation is used to overcome the chronic toxicity problems presented by systemic administration and to make retinoid therapy available as an option for the treatment of fibrotic lung disease , emphysema , and the prevention and treatment of epithelial cancers of the respiratory tract , especially those that are associated with tobacco use . retinoids are administered by inhalation to the respiratory tract of the individual as an air - borne composition with a metered dose aerosol - producing inhaler , in which the retinoid is dissolved in a combination of a pharmaceutically acceptable chlorofluorocarbon propellant and an alkylamine solubilizing agent .