Understanding pressurized metered dose inhaler performance.

INTRODUCTION: Deepening the current understanding of the factors governing the performance of the pressurized metered dose inhaler (pMDI) has the potential to benefit patients by providing improved drugs for current indications as well as by enabling new areas of therapy. Although a great deal of work has been conducted to this end, our knowledge of the physical mechanisms that drive pMDI performance remains incomplete. AREAS COVERED: This review focuses on research into the influence of device and formulation variables on pMDI performance metrics. Literature in the areas of dose metering, atomization and aerosol evolution and deposition is covered, with an emphasis on studies of a more fundamental nature. Simple models which may be of use to those developing pMDI products are summarized. EXPERT OPINION: Although researchers have had good success utilizing an empirically developed knowledge base to predict pMDI performance, such knowledge may not be applicable when pursuing innovations in device or formulation technology. Developing a better understanding of the underlying mechanisms is a worthwhile investment for those working to enable the next generation of pMDI products.