Formulating Drugs for Inhalers and Stability Issues

Abstract

The main topic addressed in this paper is the formulation of pressurised metered dose inhalers and the problems associated with formulating medications for high pressure systems. Formulations for pressurised metered-dose inhalers (pMDIs) generally consist of two main types, solution and suspension-based systems. In the latter version, the active ingredient ideally remains mainly in the solid state, which can thus reduce problems with chemical degradation. However, the physical stability of such systems, in terms of aggregation, flocculation, creaming, sedimentation, propellant clathrates and bridging can then become problematic. The problems associated with solution-based systems revolve around the chemical stability of the active ingredients.