Cellulose polymers for the constant release of a water-insoluble benzodiazepine

The realization of programmable constant release oral dosage forms designed for the extended release of a water-insoluble benzodiazepine (diazepam), is described. The dosage forms are constituted by hydrophilic matrix tablets which are obtained by direct compression of the drug with two different kinds of cellulose ethers: a water swellable polymer (cross-linked sodium carboxymethylcellulose), which acts as dissolution rate enhancer of the drug, and a water gelling polymer (hydroxypropylmethyl cellulose). In vitro tests showed that the presence of the enhancer leads to a remarkable improvement in the dissolution behaviour of the benzodiazepine. The matrices, after the contact with the dissolution medium, are subject to both gelation and erosion processes and they appear to be capable of releasing the drug at a nearly constant rate until almost the entire drug content is released.