Influence of glyceryl palmitostearate on release behaviors of hydroxypropyl cellulose microcapsules containing indomethacin by W/O emulsion

Hydrophilic hydroxypropyl cellulose (HPC) microcapsules containing the indomethacin model drug were prepared using the water in oil (W/O) emulsion method. The effect of hydrophobic glyceryl palmitostearate (Precirol ATO 5) on the release behavior as well as the drug loading and encapsulation efficiency of the indomethacin-loaded microcapsules was investigated as a function of the Precirol ATO 5 content. The microcapsules formed showed stable and spherical forms, whose particle sizes ranged from about 20 to 152 μm. X-ray diffraction analyses indicate that the indomethacin in the microcapsules was distributed in the form of molecular or very small crystals. The drug loading and encapsulation efficiency of the microcapsules slightly increased with increasing surfactant and Precirol ATO 5 content. In the dissolution test, pure HPC microcapsules showed rapid drug release, whereas HPC microcapsules containing Precirol ATO 5 showed a slower release rate. This behavior might be attributable to the hydrophobic Precirol ATO 5 coating on indomethacin, leading to the delayed effect on drug release in the medium. [Figure not available: see fulltext.]