Ethogel topical formulation for increasing the local bioavailability of 5-fluorouracil: a mechanistic study

5-Fluorouracil (5-FU) is an anticancer drug and is considered a gold standard for the treatment of skin cancer. At present, topical chemotherapy with 5-FU is associated with the limitations of poor skin permeation, retention at target site, and skin irritation potential. In the present study, an attempt has been made to develop an ethosome-based topical gel formulation (ethogel) for skin targeting of 5-FU. The ethosomal formulation was prepared using the classical dispersion method, and loading of 5% w/w of the drug was optimized to the commercial strength of marketed 5-FU cream. Carbopol 934P was used as a gel former in 0.5, 0.75, 1.0, and 1.5% w/w concentration for preparation of ethosome-based ethogel formulation. The ethogel formulation was characterized for viscosity, spreadability, extrudability, and pH. Viscosity of the developed ethogel and that of the marketed formulation was found to be 3070±14.7 and 2870±14.4 cP, respectively. An in-vitro skin permeation and deposition study was carried out across rat skin using the marketed cream and 5-FU drug solution as controls. The amount of drug deposition was found to increase 5.9- and 9.4-fold on treatment with ethogel in comparison with the marketed cream and drug solution, respectively. The result of antitumor activity evaluated using a Cytoselect 96-well cell transformation assay revealed a large reduction in tumor density with treatment with the 5-FU ethogel formulation in comparison with the marketed formulation. A significant reduction in the skin irritation potential of 5-FU ethogel formulation was also found in comparison with that of the marketed formulation as measured by the Draize test. The results of the present study demonstrated ethogel as a better alternative for increasing the local bioavailability of 5-FU in comparison to the marketed formulation.