Formulation and comparative evaluation of controlled release diclofenac tablets prepared by matrix‐embedding technique, membrane barrier technique, and combination of the two

The need for controlled release formulations of diclofenac sodium (DFS) tablets is well recognized. In this study, controlled release tablets of DFS were formulated using ethyl cellulose as retardant by matrix‐embedding technique, the membrane barrier technique, and a combination of the two. Tablets of all the formulations were found to be of good physical quality with respect to appearance, drug content uniformity, hardness, weight variation, friability, and coat thickness uniformity. In vitro release rate studies showed that increasing the proportion of ethyl cellulose extended the release of DFS. In the case of polymer‐coated tablets, an increase in the thickness of the coat (by increasing the concentration of the coating solution or by increasing the number of coats applied) controlled and extended the release. The release pattern was found to follow Higuchi’s square root kinetics in matrix‐embedded tablets and zero‐order kinetics in polymer‐coated tablets. However, for an ideal controlled release formulation of water‐soluble drugs like DFS, a combination of both matrix‐embedding and the membrane barrier technique was found to be a better proposition for extended release beyond 12 h. Such formulations exhibited dual control: matrix‐embedding controlled the release rate in the initial 3–4 h of release and membrane coat‐controlled the release profile after that. At pH 6.8, the release rate was higher, probably due to increased solubility of DFS and/or increased swelling of ethyl cellulose at higher pH. However, reduction in the granule size in matrix‐embedded tablets provided a more controlled and extended release due to more tortuosity and compaction. All the formulations were found to be highly stable and possessed reproducible release kinetics across the batches. Drug Dev. Res. 53:1–8, 2001.