Effect of Permeation Enhancers on Transdermal Delivery of Venlafaxine Hydrochloride from Carbopol Gel

In this study, we investigated the effect of different permeation enhancers at different concentrations viz. oleic acid, olive oil and castor oil from transdermal gel for transdermal delivery of venlafaxine, a newer antidepressant. It is a first line drug in the treatment of depression and inhibits brain serotonin and norepinephrine neuronal reuptake. It is also used in the treatment of anxiety disorders. Transdermal delivery of venlafaxine hydrochloride may result in enhanced patient compliance by reducing the incidence of the undesirable GI problems associated with its multiple oral dosing. The differential scanning colorimetry study was used to investigate the drug-polymer interaction. The prepared gels were evaluated for several physico-chemical parameters such as drug content, spreadability, pH, viscosity and physical appearance to justify their suitability for topical use. The in vitro permeation studies were performed by using Franz diffusion cell and rat skin as a semi permeable membrane. This indicate that penetration enhancers in 5% v/w concentration enhance the permeation of venlafaxine hydrochloride but oleic acid show maximum permeation rate was 197 μg/cm/hr as compared to olive oil (154.69μg/cm/hr) and castor oil (175.8μg/cm/hr). It is further optimized by increasing the concentration of permeation enhancer at levels as high as 10% v/w and 15% v/w. The result indicates that increase in the concentration of enhancer enhances the percutaneous permeation of venlafaxine. Oleic acid was found to be superior to olive oil and castor oil implying the ability of oleic acid to increase the drug diffusion by SC lipid disruption and increase partition coefficient into SC. The permeation rate of venlafaxine hydrochloride with 15% v/w oleic acid was higher (rat abdominal skin flux = 8.507 μg/cm/h) than with 15% v/w olive oil and castor oil. These studies show promising potential of transdermal patches of venlafaxine.