Effect of type and concentration of release-retarding vehicles on the dissolution rate of diltiazem hydrochloride from liquisolid compact

Liquisolid compacts of diltiazem hydrochloride (DTZ) were prepared using three different methods to sustain the drug release rate. Ethyl cellulose, hydroxypropyl methylcellulose and Sterotex were used separately in this study as adjuvant in the first method of preparation and as carriers in the second method. These two methods involved the addition of the binary mixture of carrier-coating materials to the liquid medication in propylene glycol under continuous stirring. The third method of preparation involved the addition of the dispersed medication in Tween 20 to the binary mixture of carrier and coating materials. The final mixtures were then subjected to thermal analysis and flowability studies before compaction into tablets. DTZ tablets prepared by the liquisolid technique were subjected to dissolution rate studies to determine the release rate of the drug in comparison with the conventional tablets. Formulations containing HPMC prepared by the different techniques showed promising extended release of the drug, followed by formulations containing EC. Formulations containing Sterotex showed the least drug release-retardation effect. Release kinetic studies revealed that the release obeyed Higuchi’s model.