Production of enteric capsules by means of hot-melt extrusion

The aim of this study was to develop an alternative technique for enteric coating consisting of the hot-melt extrusion of coating polymers. An enteric coating polymer (PVAP or HPMC AS), premixed with a plasticizer, was extruded into hollow cylinders. The hollow pipes were filled with a model drug and both open ends of the cylinders were closed, yielding hot-melt extruded enteric capsules. Main advantages of this new technology are the continuity of the process and its application for the formulation of moisture sensitive active ingredients. The enteric capsules showed excellent gastro-resistance, since no drug release was observed after 2 h 0.1N HCl. The influence of wall thickness (0.15, 0.3, 0.5, 0.8, and 1.0 mm) of the capsules on drug release was investigated. Enteric capsules with a wall thickness of 1.0 mm were subjected to a pH gradient dissolution method, simulating passage through the gastro-intestinal tract, in order to evaluate their suitability for ileal or colonic drug targeting. Storing the capsules for 1 month at high relative humidity (RH) (60 and 75% RH) revealed that the HPMC AS capsules were superior to the PVAP capsules. It can be concluded that hot-melt extruded capsules seem suitable as an alternative for enteric coating.