Topical delivery of clobetasol propionate loaded microemulsion based gel for effective treatment of vitiligo – Part II: Rheological characterization and in vivo assessment through dermatopharmacokinetic and pilot clinical studies

Vitiligo is a non contagious acquired pigmentation disorder with limited treatment possibilities. Clobetasol propionate (CP) is the drug-of-choice for vitiligo which suppresses the immune system by reducing immunoglobulin action and causes the restoration of melanocytes leading to repigmentation of skin. However, despite being effective, its low and variable bioavailability prompt for development of novel carrier that could effectively target CP to site of action without producing undesirable side-effects. Low solubility of CP in subsequent poor in vivo bioavailability was overcome by formulating microemulsion based gel of CP (MBC) which would enhance the percutaneous transport of CP into and across the skin barrier. Comprehensive characterization of MBC was carried out for viscosity, gel strength and rheological behavior. In vitro studies revealed much higher drug release, skin penetration and enhanced skin accumulation as compared to control (Cream of CP). In vitro and in vivo occlusion studies demonstrated similar occlusiveness for MBC and control. MBC exhibited 3.16 times higher stratum corneum CP levels compared to control. Visualization of cutaneous uptake in vivo using laser scanning microscopy confirmed targeting of CP to epidermis and dermis. Dermatopharmacokinetic studies of MBC showed enhanced drug deposition of CP in skin layers. MBC was assessed for in vivo efficacy by single blind randomized pilot clinical study. The efficacy was assessed by vitiligo area scoring index (VASI) method. After completion of trial, repigmentation of vitiligo patches in patients were evaluated and scored. MBC was superior in terms of faster repigmentation and efficacy when compared with control (p value<0.5). Hence, it was concluded that CP loaded MBC possess enhanced skin localization as well as therapeutic activity in vitiligo patients.