Design and release kinetic pattern evaluation of indomethacin microspheres intended for oral administration

Indomethacin has been incorporated into either ethylcellulose (EC) or Eudragit RL microspheres by a solvent-evaporation process. Production variables have been tested in an attempt to produce indomethacin microspheres having adequate oral controlled-release properties. In spite of high drug content in the ethylcellulose microspheres, the indomethacin release rate was too slow and incomplete. Although the addition of an hydrophilic polymer, poly(ethylene glycol), to the EC polymer enhanced the indomethacin release rate, it was not possible to reach release profiles suitable for oral use. Therefore, indomethacin was incorporated into a more permeable polymer, Eudragit RL. While incorporation efficiency decreased with increasing initial concentration of indomethacin, adequate oral-release profiles were achieved. It was found that all the global-release profiles yielded by the indomethacin-loaded Eudragit RL microspheres conformed to the Higuchi diffusional model of dispersed drug particles in spherical micromatrices and not to the desorption kinetic model of a dissolved drug from a monolithic spherical device.