In Vitro Dissolution for Inhalation Products

This chapter describes several approaches that have been developed for the characterization and understanding of the dissolution in the lung environment. Inhalation products have been developed to treat locally the lungs. All the in vitro dissolution methods developed and investigated so far have either used directly the whole dose powder or the fractions collected after in vitro deposition. The wide surface area provided by the lungs is covered with 10-30 ml of lung fluid, airway surface liquid, which has the double function to protect the bronchiole and alveolar surfaces from damage and to prevent foreign bodies entering the lungs. Several media have been prepared to simulate the lung fluid, and their composition tends to contain the same ion concentrations as the human lung fluid. Scientists have explored the possibility to develop a pulmonary biopharmaceutical classification system, similarly to that developed by Amidon and co-workers for oral administration.