Development and Characterization of Transdermal Microemulsion Gel for an Antiviral Drug

The objective of this study was to design and develop o/w microemulsion for transdermal delivery of poorly water soluble acyclovir by aqueous titration method. Oleic acid: castor oil (3:1), tween 80, and ethanol were selected as oily phase, surfactant and cosurfactant respectively. The Pseudoternary phase diagrams were constructed by aqueous titration method. The cosurfactant affect the shape and extant of microemulsion regions. Ethanol (cosurfactant) is expected to disorder the interfacial film gave extended microemulsion zones by destabilizing the liquid crystalline phase. Largest Microemulsion single phase region was found at Smix (2:1) than the system at other Smix. Characterization of microemulsion were done for droplet Shape and size, refractive index, pH, Viscosity, drug loading capacity. The mean droplet size of microemulsion was found below 50 nm. The maximum solubility of ACV in microemulsion system was found to be 47.4 mg/ml. The ex-vivo skin permeation studies were done using skin of Wistar albino rat by Franz diffusion cell, and microemulsion formulation MEC1 exhibited highest flux, was found to be 238.1±4.87 μg/cm/hr, while flux of MEGel, aqueous solution and conventional emulsion of ACV were found to be 230.40±6.23 μg/cm/hr, 2.47±0.76 μg/cm/hr and 8.65 ±1.21 μg/cm/hr respectively. The pharmacokinetic parameters of MEGel after topical application to the Wistar albino rat skin were significantly different from those of ACV in aqueous solution (PD) and conventional emulsion (CE). It can be concluded that microemulsion of ACV prepared with Oleic acid: castor oil (3:1) as oily phase, tween80 as surfactant, and ethanol as cosurfactant can be used as transdermal drug carrier for this and other poorly water soluble drug.