Does the United States Pharmacopeia Throat Introduce De-agglomeration of Carrier-Free Powder from Inhalers?



Publication Details

Patricia Tang, P., Philip Chi Lip Kwok, Zhenbo Tong, Runyu Yang, Judy Agnes Raper & Hak-Kim Chan, (2012), Does the United States pharmacopeia throat introduce de-agglomeration of carrier-free powder from inhalers?, Pharmaceutical Research, 29 (7), 1797-1807.


Purpose We hypothesize that the USP induction port may deagglomerate carrier-free powder emitting from dry powder inhalers (DPIs).

Methods Aerosols emitting from a range of DPIs (Spinhaler®, Turbuhaler® and OsmohalerTM) and induction ports (USP throat, straight tube, Alberta idealized mouth-throat geometry (AG)) were sized by laser diffraction. Total drug recovery was obtained by HPLC and fine particle fraction computed. Air flow patterns were simulated using Computational Fluid Dynamics (CFD).

Results The straight tube did not de-agglomerate emitted powder. However, the USP throat and AG further de-agglomerated powders from the Spinhaler, but not the Turbuhaler and Osmohaler. While budesonide powder deposited similarly in all induction ports, deposition was significantly higher in the AG for both DSCG and mannitol. CFD revealed agglomerates impacting on the USP throat with higher localized velocity compared with the straight tube. CFD further showed a more complex flow pattern with high-velocity air jets in the AG, which explains the higher FPF for DSCG and the lower FPF for mannitol using the AG.

Conclusion The USP throat further de-agglomerated the emitted powder from the DPI when it did not sufficiently disperse the powder. Other tools such as laser diffraction may be used for cross-examining to avoid artifacts in the results.

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