Dry powder inhalers under the microscope

Abstract

The application of dry powder inhalers (DPIs) in inhalation therapy has increased significantly over the last few decades. Three major factors have driven the change, the need to eliminate the use of ozone layer depleting chlorofluorocarbon propellant systems employed in the formulation of metered dose inhalers (MDIs); the wider application of DPIs beyond asthma therapy to include local delivery of mucolytics, antibiotics, antitubercular and anticancer agents and, in the systemic delivery of insulin, analgesics and drugs for erectile dysfunction. Scanning electron microscopy (SEM) has improved the general understanding of the physical properties of DPI formulations and has facilitated elucidation of the effects of carrier morphology and surface characteristics; humidity; drug to carrier ratio and mixing, on the performance on DPIs. In this article we have employed scanning electron microscopy to follow the formulation of DPIs containing lactose as carrier and the micronized drugs, salbutamol sulphate (SALB), disodium cromoglycate (DSCG), terbutaline sulphate (TERB) and beclomethasone dipropionate (BMDP). The results provide a deeper understanding of formulation variables affecting the performance of DPIs.

Keywords: Dry powder inhalers, scanning electron microscopy, drugs, carriers, drug-carrier mixtures

Journal of Pharmaceutical and Allied Sciences, Vol. 7 No.4 (2010)