Understanding the in vivo performance of enteric coated tablets using an in vitro-in silico-in vivo approach: Case example diclofenac

Individual pharmacokinetics after administration of enteric coated tablets are often highly variable and this has been ascribed to the interaction of the dosage form with the physiology of the gastrointestinal tract. This research aimed to explore the influence of interactions between enteric coated tablets and physiological factors such as gastric and intestinal pH as well as gastric emptying on the release of drug from the dosage form and the subsequent plasma profile, using diclofenac as a case example. A physiologically based pharmacokinetic (PBPK) model for monolithic enteric coated dosage forms was designed and coupled with biorelevant dissolution results to predict PK profiles of diclofenac from Voltaren® tablets in both fasted and fed humans. The paddle method was used to obtain the dissolution profiles of diclofenac in biorelevant media. The Noyes–Whitney model was employed to describe the dissolution kinetics. The PBPK model was set up using STELLA® software. A single unit enteric coated tablet was assumed to be emptied from stomach only with the house-keeping wave. Timing of the emptying was simulated using a random number generator to statistically estimate gastric emptying times after ingestion. The lag times and the dissolution rate used as input parameters in the STELLA® model were adjusted according to the pre-exposure period. The oral PK profiles were predicted for each virtual subject individually, and then the mean profiles and standard deviations were calculated. The dissolution profiles were highly affected by the period of pre-exposure in FaSSGF. A long period of pre-exposure of the tablet prolonged the lag time and decreased the dissolution rate. The results of the pharmacokinetic simulations showed that not only the mean profiles in the fasted state but also the variability could be predicted successfully using data generated for the individual virtual subjects. The results emphasize the importance of accounting for the range of pH profiles and gastrointestinal transit in the target population when predicting plasma profiles of enteric coated dosage forms and point to problems in demonstrating bioequivalence for dosage forms of this type.