One of the most crucial attributes for a Dry Powder Inhaler (DPI) products is the emitted dose (ED). With hard capsule for DPI this performance parameter is often linked to the relative humidity of the filled capsules which can have an impact on powder retention in the capsule and in the inhalation device. The emitted dose is also linked to the quality of the puncture which will allow to securely empty the capsule. The objective of this study was to evaluate the impact of various parameters believed to influence the performance of the hypromellose capsules used in conjunction with two commercial DPI devices.

Both types of hypromellose capsules (Vcaps^® and Vcaps^® Plus) are associated with low lactose retention in DPI applications, but prone to slightly more lactose retention under low relative humidity conditions. We speculate that lactose retention may be associated with the static charges that are not dissipated so readily under low relative humidity conditions.

Vcaps^® and Vcaps^® Plus capsules are shown to exhibit cleaner puncture when respectively tested with Handihaler® and Breezhaler® than hard gelatin capsule under low water content conditions.