Developing in vitro dissolution tests for orally inhaled drug products

The fate of inhaled drug substances, in vivo, is not well-understood but is believed to be dependent, to some extent, on dissolution characteristics.

This paper presents work to develop an in vitro apparatus and standardized methodology for quantifying the dissolution behavior of orally inhaled drug products. The developed solution incorporates an aerosol dose collection apparatus that collects the dose over a large area, and a modified USP Apparatus V Paddle Over Disc for dissolution testing. The discriminating ability of this solution was demonstrated via testing with a range of commercially available orally inhaled drug products (MDIs and DPIs). Good correlation was observed between in vivo mean absorption time and in vitro dissolution half-life. It is concluded that the developed solution has potential for compendial and QC testing and in the development of both branded and generic orally inhaled drug products.