Development of a standardized dissolution test method for inhaled pharmaceutical formulations

The aim of this research was to investigate a potential standardized test method to characterize the dissolution properties of formulations intended for pulmonary delivery. A commercially available dissolution tester was adapted to be used as a testing apparatus by incorporation of a membrane containing cassette. The cassette was designed to enclose previously air-classified formulations, so that they could be uniformly tested in the dissolution apparatus. The influence of particle size, amount of drug loading, and the composition of a simulated lung fluid (SLF) dissolution media on the dissolution rate were studied. Dissolution rate was significantly affected by the uniformity of drug loading, and particle size. Diffusion coefficients, estimated using the Higuchi model, showed an increase from 2.28 to 9.60 × 10−7 cm2/h as the particle size decreased. Addition of DPPC (0.02%, w/v) to the SLF dissolution media resulted also resulted in an increase in the diffusion coefficient value. This study demonstrated that the developed method was reproducible and may be used to evaluate the dissolution properties of pharmaceutical inhalation products following their aerodynamic particle classification.