POSSIBILITY ASSESSMENT OF WATER-IN-OIL MICROEMULSION FOR DERMAL DELIVERY OF PIROXICAM

Abstract

This study aimed to assess the possibility of water-in-oil (w/o) microemulsion (ME) for dermal delivery of piroxicam in terms of solubility power and in vitro release. Six blank MEs were prepared from different ratios of Tween 80, Span 80, isopropyl palmitate, isopropyl alcohol and water. A blank ME providing the highest piroxicam solubility was selected for preparation of piroxicam-loaded ME. The obtained product was investigated for tendency of stability when kept in light-protected glass containers at room temperature (28 ± 2°C) for two months. It was then evaluated in vitro drug release through dialysis membrane by modified Franz diffusion cells comparing with 0.5% w/w piroxicam commercial gel. The results indicated that piroxicam solubility in MEs was related to solubilization ability of the components. According to solubility data, piroxicam-loaded ME could be prepared with drug content of only 0.3% w/v. It was stable under the investigated conditions. In vitro release data indicated that the piroxicam-loaded ME could provide gradual drug release; however, a lag time of 0.5 h was observed and the amount of released drug was significantly lower than that from the commercial gel. In conclusions, the studied w/o ME could be used for production of 0.3% piroxicam-loaded ME having high tendency of stability. Nevertheless, the drug solubility and release results exhibited that this w/o ME was unsuitable for piroxicam incorporation. The interaction between drug and components as well as microstructure of ME may be a crucial parameter for therapeutic efficacy since it could adversely influence drug solubility and release.