Effect of processing variables on the release and particulate properties of sustained release amoxicillin microcapsules prepared by emulsion solvent evaporation.

This study reports the preparation of amoxicillin microcapsules by an emulsion solvent evaporation process. In particular the effect of processing variables including the dimension and position of stirring paddle and container; volume of continuous phase versus dispersion phase; stirring speed and encapsulation temperature on the release and particulate properties of the amoxicillin microcapsules were determined. When the diameter of the paddle was half of that of the container and the clearance between the paddle and the bottom of the vessel was 1/4 of the total volume in the vessel, almost no material stuck to the inside wall of the beaker and uniform microcapsules were prepared. Very uniform, round microcapsules were also prepared with a high yield when V(acetone): V(light mineral oil) = 1 : 3 and 1 : 5 because these systems ensured the formation of uniform emulsions. Physical evaluation of the microcapsules also showed that optimum drug release was achieved when the microcapsules were round, did not aggregate, were protected from the burst effect, the stirring speed for preparation was between 600-800 rpm and evaporation temperature was 25 degrees C. Microcapsules prepared using these ideal conditions achieved constant amoxicillin release for up to 12 h.