Utility of Mixture of Commercially Available Polymers as Constituents of Sustained-Release Microcapsules Containing Cefadroxil or Theophylline

Hydroxy propyl methyl cellulose acetate succinate high grade (AS-HG) and ethyl cellulose (EC) mixture microcapsules containing cefadroxil or theophylline were prepared by a solvent evaporation method in liquid paraffin dissolved sorbitan tristearate as a dispersing agent, and their sustained-release properties were evaluated. The microcapsules prepared with AS-HG : EC (in a 2 : 5 weight ratio) mixture containing 20% of cefadroxil or theophylline exhibited apparent zero-order releasing pattern in pH 6 to 8, at 50rpm and 37°C (paddle method). These microcapsules were administered orally to beagle dogs and the plasma concentrations of cefadroxil or theophylline were measured periodically. As a result of in vivo investigation, a satisfactory sustained-release plasma pattern and an apparent zero-order process in the gastrointestinal absorption were confirmed by deconvolution analysis of both drugs.