Microemulsion based bioadhesive gel of itraconazole using tamarind gum: in-vitro and ex-vivo evaluation

The current study was aimed to formulate and evaluate bioadhesive gel containing microemulsion (ME) of itraconazole (ITZ) and an attempt was made to investigate suitability of tamarind gum (TG) as a gelling agent. The solubility of ITZ in oils, surfactants and co-surfactant was evaluated for the selection of appropriate component. The ratio of surfactant and co-surfactant was optimized by constructing pseudoternary phase diagram. Ternary phase diagram was constructed using isopropyl myristate (IPM) and oleic acid (OA) as oil phase, tween 80 as surfactant and isopropyl alcohol (IPA) as cosurfactant in order to obtain ME region. The optimized ME of ITZ was characterized by its qualitative and quantitative tests and incorporated into polymeric gels of carbopol (CBP), xanthan gum (XG) and TG. The ME based ITZ gels were evaluated for pH, drug content, viscosity, ex-vivo bioadhesion, spreadability and in vitro drug release. Furthermore, antifungal activity of the gels was performed by agar cup diffusion technique using cultures of Candida albicans. ITZ showed maximum solubility in mixture of IPM and OA (1:1). Stable ME was obtained when IPM and OA was taken in the ratio of 1:1 as oil phase, Tween 80 as surfactant and isopropyl alcohol (IPA) as cosurfactant at the weight ratio of 10:45:45. The optimized ME based gels showed pH in the range of 6.11 to 6.48, spreadability in the range of 4.1 to 7.1gm.cm/sec and ex vivo bioadhesion in the range of 65 to 84gm. The viscosity study indicated pseudoplastic behaviour of all ME based gel formulations. Amongst the studied ME gels, TG containing gels exhibited fast and complete drug release at the end of 24h. Formulation F7 containing TG showed wide zone of inhibition and found to be stable for three months. These results indicate that the TG containing ME gel may be a used as vehicle for topical delivery of drugs.