Abstract

A study was undertaken to formulate sustained release tablets by utilizing the bi-layer concept. The formulation contained a fast release layer and a sustaining layer. Ethylcellulose and rosin were used as the matrix forming materials. Matrix tablets of diltiazem hydrochloride were formulated using ethylcellulose or rosin as matrix materials in various quantities (%w/w) to study their ability to retard the release and were evaluated for hardness, friability and drug release. In vitro release from the formulation was studied as per the USP XXlll dissolution procedure. The formulations gave an initial burst effect followed by sustained release for 12 h which indicates bimodal release of diltiazem HCI from the matrix tablets. The data obtained were fitted into Higuchi's models. Analysis of n values of Korsmeyer equation indicated that the drug release involved both diffusional and dissolutional mechanisms.