Novel starch-based PVA thermoplastic capsules for hydrophilic lipid-based formulations

For decades, gelatin has been used in the rotary die process as a shell-forming material of soft capsules because of its unique physicochemical properties. However, with respect to the encapsulation of comparatively hydrophilic lipid-based formulations, gelatin has one considerable drawback: Immediately after production, the capsule shell contains a large amount of water (up to 35%). There is the potential for water to migrate from the capsule shell into the formulation, which will lead to a decrease in drug solubility and, in turn, the potential for drug crystallization. The present study introduces a novel capsule material that was obtained from extrusion. The starch-based polyvinyl alcohol thermoplastic capsules (S-PVA-C) mainly comprised a blend of starch and PVA. Gelatin and the novel material were used to encapsulate a hydrophilic lipid-based system of fenofibrate. Considerable water migration was observed from the soft gelatin shell to the hydrophilic formulation during drying and drug crystallization resulted in soft gelatin capsules. In contrast, S-PVA-C displayed no substantial water exchange or drug crystallization upon storage. The thermoplastic capsule material further exhibited more surface roughness and higher resistance to mechanical deformation compared with gelatin. In conclusion, S-PVA-C provided a robust drug product following encapsulation of a rather hydrophilic lipid-based formulation.