Predicting the human in vivo performance of different oral capsule shell types using a novel in vitro dynamic gastric model

The disintegration of a capsule shell may determine the onset of drug dissolution from capsule formulations. In this study, the release of a rapidly dissolving model drug (paracetamol), from two hydroxypropyl methylcellulose capsules containing either carageenan (HPMC-C) or gellan gum (HPMC-G) and one hard gelatin (HG) capsule, were investigated using a conventional in vitro model, the USP dissolution apparatus I, and a novel in vitro model of the human gastric compartment, the dynamic gastric model (DGM). The results obtained in vitro were compared with in vivo gamma scintigraphy human data and in vivo gastric emptying profiles available in the literature. The drug release from HPMC-G capsules, observed with the USP dissolution apparatus I, was delayed with respect to the other two capsules, while the results obtained from the DGM in the fasted state were closer together, which was in agreement with data from the in vivo studies. In the fasted state, the capsule rupture times obtained from the DGM were similar to those observed by gamma scintigraphy in vivo studies. In the fed state, the ‘apparent’ rupture times observed with the DGM were delayed compared to fasted, and were even longer than those observed by scintigraphy in vivo for HPMC-G and HG capsules. However, these discrepancies can reasonably be explained by considering the impact of food upon dispersion of the capsule contents and the sampling from the DGM, when compared to the human scintigraphy experiments.