Sustained release of acetaminophen from a heterogeneous mixture of two hydrophilic non-ionic cellulose ether polymers.

This study examined the release of acetaminophen (APAP) from hydroxypropyl methylcellulose (HPMC) and hydroxypropyl cellulose (HPC) matrices. The effect of pseudoephedrine (PE) as a co-active, HPMC:HPC ratio, polymer loading, pH of the dissolution media, and compression force on APAP release were studied. Granules formulated with APAP or both APAP and PE, and various blends of HPMC and HPC were compressed into tablets at different compression forces. APAP release from the matrix tablets was not considerably influenced by changes in HPMC:HPC ratio or compression force. The rate of drug release was significantly affected by pH of the dissolution media, total polymer loading, and the presence of PE. Drug release from the formulations containing both APAP and PE was slower than those containing only APAP. Drug release from tablets formulated with APAP only showed an initial burst at pH 1.16 or 7.45. Formulations containing both APAP and PE showed slower drug release at pH 1.16 than at pH 7.4. The drug release data showed a good fit to the Power Law Model. The mechanism of drug release is consistent with a complex behavior. The results of the tablet erosion studies indicated that the amount of APAP released was linearly related to the percentage of tablet weight loss. The kinetics of tablet water uptake was consistent with a diffusion and stress relaxation mechanism.