Development of a multiple-unit tablet containing enteric-coated pellets

Film coating of pellets is a common way to design modified-release systems. The aim of this study was to produce a multiple-unit tablet compressed from enteric-coated pellets. The dosage form should comply with Pharmacopoeial demands, especially regarding dissolution, but preferably also all other parameters, including sufficient hardness for packaging procedures. Various approaches, such as using different cushioning excipients, using different enteric coating polymers, changing the tablet shape, and application of an additional protective coating, were employed to develop the dosage form. The final formulation released 9.0 ± 1.8% of the drug in an acidic medium and was compliant regarding uniformity of mass, content, and friability, and had a hardness of 59 N. An optimal coating was obtained by mixing two acrylic polymers: relatively brittle Eudragit® L30 D-55 with more flexible Eudragit® FS 30 D. A mixture of Avicel® PH 101 as filler and Kollidon(®) VA 64 as dry binder was found to be optimal as a cushioning excipient. It was found that tablet shape and an additional protective pellet coating of Kollidon(®) VA 64 were the key elements for this development. A biconvex tablet shape was found to approximately halve the release in an acidic medium compared to a round flat-faced tablet.