Carrier-free high-dose dry powder inhaler formulation of ibuprofen: Physicochemical characterization and in vitro aerodynamic performance

Objective: To investigate influences of capsule fill weight, batch size, and storage conditions on in vitro aerodynamic performance of jet-milled ibuprofen (IBU) carrier-free, dry powder inhaler formulations.

Materials and methods: Milled and unmilled IBU samples were characterized thermally and spectroscopically. Physicochemical characterization was performed by quantifying specific surface area, density, and angle of repose. Performance testing was conducted on IBU formulations in combination with a high resistance Monodose RS01 using Next Generation Impactor.

Results and discussion: There were no detectable differences between IBU samples thermally and spectroscopically. The milled IBU sample exhibited improved powder flow in comparison with the unmilled sample. The milled IBU powders possessed surprisingly high in vitro aerodynamic performance with a fine particle fraction percentage between 67 and 85%, and a minimum respirable fraction percentage of 49%. The capsule fill weights, from 10 to 50mg, and milling batch sizes did not significantly influence performance. The importance of powder conditioning following milling was illustrated as the storage duration and temperature negatively affected performance.

Conclusion: In vitro aerodynamic performance of IBU is independent of capsule fill weight and batch size; however, some period of powder conditioning is recommended to reduce variability in formulation performance.