Formulation, Optimization and Evaluation of Organogel for Topical Delivery of Acyclovir

The conventional acyclovir topical therapy has a low efficacy, due to the lack of penetration of a sufficient amount of drug to the target site.

The aim of this work was to formulate and optimize organogel containing acyclovir to enhance the penetration and retention time of acyclovir in the basal epidermis, site of Herpes simplex virus infections.

Microemulsion based organogel containing acyclovir was developed using the combination of surfactants, polar and nonpolar solvents. To investigate the microemulsion and gelling region, titration was carried out and pseudoternary phase diagram was constructed. The formulation was optimized by using 3-factor, 3-level, Box-Behnken design. Response surface plots were constructed for various response variables, viz. % drug permeation, viscosity and spreadability. The optimized formulation was searched utilizing overlay plots and desirability of the response. The optimized formulation was further characterized for microscopy, pH, ex-vivo permeation etc. Ex-vivo skin permeation showed first order drug diffusion through the skin and was found being stable upto 8 hrs.

In case of developed organogel formulation, significantly higher amount of acyclovir was observed to be retained in the skin, as compared to retention observed with the conventional cream.

The results show that the ACV organogel penetrates into the skin and form the reservoir that can slowly release the drug for a longer period and may control viral growth more effectively.