The use of computational fluid dynamics in inhaler design.

INTRODUCTION Computational fluid dynamics (CFD) has recently seen increased use in the design of pharmaceutical inhalers. The use of CFD in the design of inhalers is made difficult by the complex nature of aerosol generation. At present, CFD has provided valuable insight into certain aspects of inhaler performance, though limitations in computational power have prevented the full implementation of numerical methods in the design of inhalers. AREAS COVERED This review examines the application of CFD in the design of aerosol drug delivery technologies with a focus on pressurized metered-dose inhalers (pMDI), nebulizers and dry powder inhalers (DPIs). Challenges associated with the application of CFD in inhaler design are discussed along with relevant investigations in the literature. Discussions of discrete element modeling (DEM) and the simulation of pharmaceutical aerosol dispersion are included. EXPERT OPINION The extreme complexity of coupled fluid and aerosol dynamics associated with aerosol generation has somewhat limited the use of CFD in inhaler design. Combined CFD--DEM simulations provide a useful tool in the design of DPIs, though aerosol generation in pMDIs and nebulizers has eluded CFD modeling. The most beneficial use of CFD typically occurs when concurrent CFD and experimental analyses are performed, significantly enhancing the knowledge provided by experiment alone.