The relationship between mucoadhesive polymers and surface coating in tablets for the controlled colonic delivery of a poorly water-soluble drug

Background The mucoadhesive polymers play an important role in targeted and controlled drug delivery. Objectives This study aimed to investigate the drug release behaviour and interpret the role of mucoadhesive polymers involved in the coating layer of mucoadhesive tablets for the sustained release of a poorly water-soluble drug. Methods A solid dispersion of prednisolone and zein was used in the core tablets created with two mucoadhesive polymers, which included Carbopol 940 and hydroxypropyl methylcellulose K4M. In addition, the properties of a single-layer coating, created from the combination of zein and Kollicoat MAE 100P to delay release through the upper parts of the gastrointestinal tract, were investigated in the presence of the above mucoadhesive polymers; these properties included drug dissolution, mucoadhesion, surface morphology, swelling and erosion. Results The mucoadhesive polymer concentrations and types were integrated not only into the core tablets through a swelling/erosion mechanism but also into the surface polymer coatings for controlled drug release. HPMC was preferred in the formulations due to the ability to form pores on the surface coating, allowing water uptake so that the coating could control drug release for a later stage via a swelling/erosion mechanism. Conclusion The proposed mechanism determined in this project could be beneficial in the selection of polymers for applications targeting the colon with coated mucoadhesive tablets.