The objective of the present study was to check for the possibility to successfully predict individual in vivo dissolution/absorption profiles resulting from fasted administration of a diclofenac extended release pellet formulation. For this purpose dissolution profiles were generated with different dissolution setups using a set of media reflecting pH-conditions in the different segments of the gastrointestinal tract. Since gastric emptying of pellets seemed to be a critical factor for in vivo drug release, a set of different gastric residence times was screened in in vitro studies. Subsequently, in vitro release profiles were first directly compared with the individual in vivo absorption profiles and in a second step a mathematical model, which had been developed in a previous study, was applied to calculate predicted individual in vivo release profiles based on in vitro release profiles and individual gastric emptying. The comparison of predicted individual in vivo release profiles and individual in vivo absorption profiles showed a high degree of similarity, thus confirming the suitability of a set of different gastric residence times used in in vitro drug release testing. Additionally, obtained results indicated that a substantial part of variability of diclofenac absorption profiles can be explained by the variability of pellet gastric emptying kinetics.
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