ABSTRACT
Traditional pressurized metered dose inhaler (pMDI) formulations contain a drug either in solution or in suspension in a compressed propellant (1). Excipients commonly found in pMDIs include surfactants, which are used for valve lubrication and/or as stabilizers, and cosolvents that serve as aids in the solubilization of amphiphiles (2,3). Several alternative propellant-based inhaler formulations have been recently proposed (4). To a large extent, these novel formulations came as a response to difficulties encountered in transitioning from chlorofluorocarbon (CFC) to hydrofluoroalkane (HFA) propellants, as dictated by the Montreal Protocol. These alternatives to solution and (micronized) dispersion-based pMDIs also provide unique opportunities for the local and systemic delivery of biomolecules to and through the lungs (5). Such advances may give propellant-based inhaler formulations the necessary edge to compete with recent developments in dry powder inhaler (DPI) technology (6).
