Biopharmaceutical evaluation of sustained-release ethylcellulose microcapsules containing amoxicillin using beagle dogs.

A beta-lactam antibiotic, amoxicillin, was microencapsulated with ethylcellulose using a solvent evaporation process in liquid paraffin containing sorbitan tristearate as a dispersing agent, and the microcapsules obtained showed first-order drug release. Usage of the previous log-log relationship of cefadroxil between in vitro dissolution half-lives (T50) and the experimental release rate constants (k'r) of the drug in vivo, and the nomogram for the design of satisfactory sustained-release preparations resulted in the prediction that ethylcellulose microcapsules containing 60% amoxicillin would show the most effective sustained-release pattern. Prepared microcapsules containing various amounts of amoxicillin were administered to beagle dogs and it was found that above prediction was correct. In addition, a more precise log-log correlation concerning amoxicillin was also undertaken, good linearity was observed and the decline was very similar to that of cefadroxil.