Dual Approach of Nanoemulsion and Natural Permeation Enhancer Endorse Skin Targeting of Acyclovir

Background: In this study, nanoemulsion based gel formulation of acyclovir was prepared in order to increase its topical effectiveness and target the disease site, which is the foremost limitation associated with the topical marketed formulations of acyclovir. Methods: In this study, nanoemulsion based gel formulation of acyclovir was prepared in order to increase its topical effectiveness and target the disease site, which is the foremost limitation associated with the topical marketed formulations of acyclovir. A w/o nanoemulsion in the strength of 5% w/w was prepared using probe sonication method and was characterized extensively in vitro, ex vivo and in vivo to determine the quantity of drug that reached into skin to effectively treat the disease. Results: Skin deposition across the rat skin was found to be 6.6 fold higher with developed nanoemulsion based gel formulation in comparison to the marketed cream. The results of enhanced skin permeation and deposition were deep-rooted by carrying out different mechanistic studies like FTIR and CLSM of skin treated with prepared formulation. The rheological characterization study depicted the shear thinning property and better structural recovery of nanoemulsion based gel (99.17 +/- 1.1%) as compared to marketed cream (95.03 +/- 0.8%). Further in-vivo localization index, which was found to be 60.33 +/- 0.9% and 19.21 +/- 0.6% for prepared gel and marketed cream, respectively, assured high skin deposition and adequate penetration of the prepared gel to the different layers of skin with no significant absorption into the systemic circulation. Conclusion: Higher drug solubility, lower particle size, higher surface area and enhanced skin permeation and deposition associated with prepared formulation seems to be responsible for its elevated skin penetration which makes developed w/o nanoemulsion based gel as effective carrier for increasing the local bioavailability of acyclovir.