Linear extended release of a water-insoluble drug, carbamazepine, from erodible matrices

The preparation and in vitro characterization of extended release erodible hydrophilic matrices containing a water insoluble drug (carbamazepine) are described. The matrices are obtained by tabletting mixtures of the drug with a water swellable polymer (cross-linked sodium carboxymethylcellulose) and a water gelling polymer (hydroxypropylmethylcellulose). These matrices appear to be subject, during in vitro tests, both to a gelation and to an erosion process and they are capable of releasing the drug at a nearly constant rate, until almost the entire drug content is released. The influence of the technological parameters of the formulation (weight ratios of polymers used, compression forces, etc.) and of the gelation and erosion processes of the matrices during the in vitro tests, on drug release are investigated.