In Vivo–In Vitro Comparison of Deposition in Three Mouth–Throat Models with Qvar ® and Turbuhaler ® Inhalers

In vitro polydisperse aerosol deposition in three mouth–throat models, namely, the USP (United States Pharmacopeia) mouth–throat (induction port), idealized mouth–throat, and highly idealized mouth–throat, was investigated experimentally. Aerosol particles emitted from two commercial inhalers, Qvar^® (pMDI) and Turbuhaler^® (DPI), were used. The in vitro deposition results in these three mouth–throat models were compared with in vivo data available from the literature. For the DPI, mouth–throat deposition was 57.3 ± 4.5% for the USP mouth–throat, 67.8 ± 2.2% for the idealized mouth–throat, and 69.3 ± 1.1% for the highly idealized mouth–throat, which are all relatively close to the in vivo value of 65.8 ± 10.1%. In contrast, for the pMDI, aerosol deposition in the idealized mouth–throat (25.8 ± 4.2%) and the highly idealized mouth–throat (24.9 ± 2.8%) agrees with the in vivo data (29.0 ± 18.0%) reported in the literature better than that for the USP mouth–throat (12.2 ± 2.7%). In both cases, the USP mouth–throat gives the lowest deposition among the three mouth–throat models studied. In summary, both the idealized mouth–throat and highly idealized mouth–throat improve the accuracy of predicted mean in vivo deposition in the mouth–throat region. This result hints at the potential applicability of either the idealized mouth–throat or highly idealized mouth–throat as a future USP mouth–throat standard to provide mean value prediction of in vivo mouth–throat deposition.