The influence of the ratio of lipid to surfactant and the presence of cosolvent on phase behaviour during aqueous dilution of lipid-based drug delivery systems

The study was designed to investigate phase behavior during dispersion of anhydrous lipid formulations, and to investigate the effect of lipid/ surfactant ratios, and the presence of cosolvent on the performance of formulations. Equilibrium phase studies were extensively conducted using three component systems to investigate the phase changes of the anhydrous formulation in response to aqueous dilution. The influence of chain length and combination of mono-, di- and tri-glycerides on the phase behavior was studied. Droplet size studies were carried out to assess the influence of lipid and surfactant on the resultant droplet size upon aqueous dilution. The study shows that mixture of mono-, di- and tri-glycerides with equal amount of surfactant can promote great absorption of water and produce efficient self-emulsification systems (particularly, self-emulsifying/microemulsifying drug delivery systems). Increasing the monoglyceride concentration within the oil component enhanced water solubilization significantly. Among the phase diagram studies, Imwitor 308/Tween 80 systems produced a large optically transparent nanodispersing region. The selection of glycerides seems to be the most vital oil component in designing optimal self-emulsifying lipid formulations.