Formulation Development and Evaluation of Acyclovir Bigel Containing Lemongrass Oil

The present study was undertaken to formulate and evaluate a topical bigel drug delivery system of acyclovir using lemongrass oil as a natural penetration enhancer , with the aim of improving drug release and suitability for topical antiviral therapy. Acyclovir, a widely used antiviral agent for the treatment of herpes simplex virus (HSV) infections, exhibits limited topical efficacy due to poor skin permeation, thereby necessitating the development of an advanced delivery system. Bigel formulations were prepared by combining a hydrogel phase based on Carbopol 934 and an organogel phase composed of olive oil and beeswax . Five formulations (TBG1–TBG5) were developed by varying the concentration of the hydrophilic polymer while maintaining a constant drug load and organogel composition. Lemongrass oil was incorporated to enhance skin permeation, and triethanolamine was used to adjust the pH of the formulations to a skin-compatible range. Preformulation studies, including melting point determination, solubility analysis, partition coefficient determination, and Fourier transform infrared (FTIR) spectroscopy, confirmed the purity, stability, and compatibility of acyclovir with the selected excipients. The formulated bigels were evaluated for organoleptic properties, pH, viscosity, spreadability, drug content, and in vitro drug release. All formulations exhibited satisfactory homogeneity, appropriate pH values suitable for topical application, and acceptable rheological properties. In vitro drug release studies demonstrated a controlled and sustained release pattern for all formulations over the study period. Among the formulations, TBG1 showed superior performance , exhibiting the highest drug content and cumulative drug release, indicating optimal polymer concentration and effective penetration enhancement. The results of this study suggest that the developed acyclovir bigel formulation represents a promising and patient-friendly topical delivery system. The incorporation of lemongrass oil highlights the potential of natural penetration enhancers in improving topical drug delivery. Overall, this work supports the suitability of bigels as an effective carrier system for the topical administration of acyclovir in the management of HSV infections.