Comparison of dissolution time profiles: No similarity but where is the difference?

The similarity of the dissolution time profiles is routinely determined by various statistical methods, e.g. by calculating the f₂ similarity factor, by calculating the multivariate statistical distance or determining the confidence interval of f₂ metrics using the bootstrapping method. If the similarity of the dissolution profiles is not achieved, these methods provide no information about the possible causes of the differences in the final dosage forms. In this article it is shown that after introduction of summary parameters into the disintegration-dissolution model (DDM), such as intrinsic lifetime distribution of particles, saturation state function, drug load of the system and applying population data analysis, differences on the level of intrinsic lifetime distributions of particles of active pharmaceutical ingredient in immediately release formulations are identified. The identification of these differences provides important clues to target development of generic formulations or helps to explain possible differences in the in vivo behavior of products.