In Vivo-Relevant Transwell Dish-Based Dissolution Testing for Orally Inhaled Corticosteroid Products

Purpose To establish an in vivo -relevant Transwell dish-based dissolution test system for the “respirable” aerosols of inhaled corticosteroids (ICSs) using marketed inhaler products. Methods “Respirable” ≤ 5.8 or 6.5 μm aerosols of 7 ICSs from 11 inhaler products were collected onto the filter membranes under the modified assembly of the cascade impactor. Their dissolution in 10 ml of the simulated lung lining fluid (sLLF) was determined over time in the Transwell dish at 37°C and ~100% relative humidity in the presence of subsequent diffusive permeation across the Transwell’s supporting membrane. Results While three ICSs with high-to-intermediate solubility enabled the first-order “sink” and complete dissolution in 6 h, 4 ICSs with poor solubility including fluticasone propionate (FP) resulted in the pseudo-zero-order “non-sink”, slow and limited dissolution. The aerosol dissolution rate constants (k diss ) were derived, well-correlated with the solubility. For FP, but not for highly-soluble flunisolide (FN), dissolution was kinetically aerosol mass-dependent. However, for a given ICS, dissolution profiles were indistinguishable between the formulations and products upon comparable aerosol mass collection. Conclusions The in vivo -relevant Transwell dish-based “respirable” aerosol dissolution test system was developed, kinetically discriminative in accordance with the ICS solubility, but indistinguishable for a given ICS between the marketed products.