Development of Poorly Water Soluble Drug Microemulsion Formulations

Abstract

Microemulsions are considered as potential systems for poorly water soluble drugs delivery because of their ability to improve both lipophilic and hydrophilic drug solubilization, thermodynamic stability and ease of preparation. Different compositions of microemulsions, containing poorly water soluble antifungal drug tolnaftate, were prepared and evaluated. Microemulsions were formulated using oil phases (isopropyl myristate, ethyl oleate), surfactant (labrasol), co-surfactant (plurol isostearique) and water. Particle size dependence on water concentration in samples without tolnaftate and containing different oil phases was determined by dynamic light scattering (DLS) method. Tolnaftate solubility capacity was evaluated in 14 experimental formulations, containing following excipients: Twen 20, Twen 80, PEG 400, and ethanol. Five different compositions with tolnaftate and isopropyl myristate as an oil phase were formulated with S/CoS ratios (4:1, 3:1) and varying water content. Pseudo ternary phase diagrams for microemulsion region were constructed. Particle size was measured by DLS method. The mean diameters of microemulsion droplets were in the range from 29 nm up to 342 nm. Experimental formulations were analyzed by optical microscopy and Raman spectroscopy. Stable formulations with narrow range of particle size distribution were produced. The ability of microemulsions to modify penetration of tolnaftate into skin in vitro will be assessed parallely to ongoing stability studies.