Development and validation of an in vitro release method for topical particulate delivery systems.

The aim of this study was to develop an in vitro release method for topical particulate delivery systems using the immersion cell in combination with paddle dissolution apparatus. Chitosan- and methacrylate-based microparticles with mupirocin were prepared and used as model topical delivery systems for method development. Diffusion of the drug occurred across a mixed cellulose ester membrane, which demonstrated low drug adsorption and low diffusional resistance. After an initial lag phase the amount of drug released became proportional to the square root of time. The method was discriminative toward differences in formulation, as well as toward differences in drug concentration inside the sample compartment. The method was further used to confirm sameness between batches of the same composition prepared by the same process. Variations in paddle rotation speed (25 rpm, 50 rpm, 100 rpm), paddle height (1cm, 2.5 cm) and volume of release medium (100ml, 200 ml) did not significantly alter the release rates. The method of analysis was validated according to ICH guidelines. Currently there are no compendial or standard methods and apparatuses for in vitro release testing of topical microparticles. The developed method can be a useful guide in formulation development of such delivery systems.