[Effect of release of hydroxypropylmethyl cellulose on single and bilayer sustained-release matrix tablets]

To study the influence of HPMC as hydrophilic matrix materials and controlled-layer components on the drug release of sustained-release matrix tablets and bilayer tablets.

Diltiazem hydrochloride was chosen as the water-soluble model drug to prepare different kinds of matrix tablets and double layer tablets with different formulations, and evaluate how the levels and grades of HPMC affect the drug release in sustained-release tablets and bilayer tablets.

HPMC with high viscosity and the amount of 20%-40% could delay the drug release to certain degree, but it was difficult to further slow down the drug release up to 24 h, especially for a water soluble drug. Combining HPMC with 5%-20% of CMC-Na was proven to be an effective way to achieve the 24 h release profile with the water soluble drug. HPMC was also investigated as a component in the double layer tablet as base layer. Drug release was complicated compared with EC as the base layer in the double layer tablet due to the great swelling ability of HPMC. HPMC's larger swilling let it form a big cap to retard the drug release, which could significantly affect the drug release with a large ratio of the base layer to the drug layer; furthermore increasing the quality of 10%-40% of the base layer and the proportion of HPMC could reduce the initial burst release.

The grade/level of HPMC and combinations with other matrix materials had a big impact on the drug release. HPMC could be used in the base layer of the double tablet to alternate the drug release profile, and reduce the initial burst release of the double-layer matrix tablet, and potentially change the drug mechanism.