When drugs plasticize film coatings: Unusual formulation effects observed with metoprolol and Eudragit RS

Comparative Evaluation of Pellet Cushioning Agents by Various Imaging Techniques and Dissolution Studies

Most of the commercially available pharmaceutical products for oral administration route are marketed in the tablet dosage forms. However, compression of multiparticulate systems is a challenge for the pharmaceutical research and industry, especially if the individual unit is a coated particle, as the release of the active ingredient depends on the integrity of the coating. In the present study, polymer-coated pellets tableted with different types of excipients (powder, granules, pellets) then were investigated by various tablet-destructive (microscopic) and tablet non-destructive (microfocus X-ray; microCT) imaging methods. The information obtained from the independent evaluation of the in vitro drug release profiles model is confirmed by the results obtained by image analysis, regardless of whether X-ray or stereomicroscopic images of the coated, tableted pellets were used for image analysis. The results of this study show that the novel easy-to-use, fast, and non-destructive MFX method is a good alternative to the already used microscopic image analysis methods regarding the characterization of particulates, compressed into tablets.

Polymer Distribution and Mechanism Conversion in Multiple Media of Phase-Separated Controlled-Release Film-Coating

Phase-separated films of water-insoluble ethyl cellulose (EC) and water-soluble hydroxypropyl cellulose (HPC) can be utilized to tailor drug release from coated pellets. In the present study, the effects of HPC levels and the pH, type, ionic strength and osmolarity of the media on the release profiles of soluble metoprolol succinates from the EC/HPC-coated pellets were investigated, and the differences in drug-release kinetics in multiple media were further elucidated through the HPC leaching and swelling kinetics of the pellets, morphology (SEM) and water uptake of the free films and the interaction between the coating polymers and the media compositions. Interestingly, the drug release rate from the pellets in different media was not in agreement with the drug solubility which have a positive correlation with the drug dissolution rate based on Noyes–Whitney equation law. In particular, the drug release rate in acetate buffer at pH 4.5 was faster than that in other media despite the solubility of drug was relatively lower, regardless of the HPC levels. It may be attributed to the mutual effect between the EC and acetate buffer, which improved the permeability of the film. In contrast, the release of drug in HCl solution was dependent on the HPC levels. Increasing the levels of HPC increased the effects of hydrogen ions on the polymer of HPC, which resulted in a lower viscosity and strength of the gel, forming the larger size of pores in polymer films, thus increasing the drug diffused from the coating film. Further findings in phosphate buffer showed a reduction in the drug release compared to that in other media, which was only sensitive to the osmolarity rather than the HPC level and pH of the buffer. Additionally, a mathematical theory was used to better explain and understand the experimentally measured different drug release patterns. In summary, the study revealed that the effects of the media overcompensated that of the drug solubility to some extent for controlled-release of the coating polymers, and the drug release mechanism in multiple media depend on EC and HPC rather than on HPC alone, which may have a potential to facilitate the optimization of ideally film-coated formulations.