In vitro diffusion studies for the assessment optimization & comparison of the drug release from various dermatological formulations of hydroquinone with that of commercially available product

Topical hydroquinone is commonly used for the purpose of lightening freckles, age spots, and other skin discolorations. This study was undertaken to develop, screen and compare various topical formulations for optimum drug release through cellulose membrane and human cadaver skin with that of commercially available product.;Various formulations containing 2% drug as opposed to the 4% strength formulation available commercially were developed using non-ionic, anionic emulsion based system and HPMC gel based system. Also the effect of penetration enhancers such as propylene glycol(PG), diethyleneglycol monoethylether(DGME) and ethanol at 5%, 10%, 15% levels of concentration were evaluated. In-vitro studies were performed with franz diffusion cells using cellulose membrane and human cadaver skin as diffusion barriers for 2 hours. The samples with optimum drug release were further studied for 12 hours period. The formulation with maximum drug release through cellulose membrane was then chosen for drug release through human cadaver skin.;Studies were also conducted on the commercially available product and release profiles were obtained for 2 hours and 12 hours study using cellulose membrane and 12 hours study using human cadaver skin.;With cellulose membrane the release was observed to be HPMC gel>anionic emulsion>nonionic emulsion. Among all the samples tested anionic emulsion with 5% ethanol gave a release of 33.7% as compared to a release of 16.98% from the commercially available product. So, the drug release from thest 2 systems was studied through human cadaver skin for 12 hours. Here the drug release pattern remained similar to cellulose membrane, but the amount of total drug diffused was reduced. These data were treated to determine various physical parameters that influence drug diffusion. The values for steady state flux and diffusion coefficient were found to be the highest, and the values for lag time and partition coefficient were the lowest.;The anionic emulsion system with 5% ethanol and 2% hydroquinone gave bioequivalence to that of commercially available preparation containing 4% hydroquinone. This study supports that with proper composition of a vehicle it is possible to develop a topical formulation with optimal drug release.