An Investigation into the Effect of Various Penetration Enhancers on Percutaneous Absorption of Piroxicam

Achieving a desirable percutaneous absorption of drug molecule is a major concern in formulating dermatological products. The use of penetration enhancers could provide a successful mean for this purpose. The aim of this study was to evaluate the effect of incorporating a few common penetration enhancers (in different concentrations) into a 0.5% w/w piroxicam (model drug) gel formulation, on the permeability rate of drug through rat abdominal skin in vitro. For this purpose various concentrations of oleic acid (OA), urea (UR), lecithin (LEC) and isopropyl myristate (IPM) were used as the penetration enhancer. In order to investigate the effect of penetration enhancers used in this study on the permeability rate of piroxicam through sections of excised rat skin, Franz-type diffusion cells were employed. The receptor phase was constantly stirring 0.9% w/v sodium chloride solution at 32°C. At set intervals up to 8h, 5ml samples were removed from the receptor compartment and the amount of piroxicam permeated through the skin calculated by determining the UV absorbance of drug at 353 nm. Results show that among the penetration enhancers used, the use of OA at a concentration of 1.0% w/w had the greatest effect on the permeability rate of piroxicam, and produced the highest enhancement ratio among all the penetration enhancers examined. The other penetration enhancers used were found to have a far smaller effect on the permeability rate of piroxicam through rat skin. The enhancement ratio of the penetration enhancers used in the formulation of piroxicam gel were found to increase in the order of OA>> IPM > LEC > UR.