SEMISOLID EMULSIFYING BASES FOR THE FILLI NG OF CAPSULES CONTAINING PEG-400 AND VEGETABLE OIL - PHYSICOCHEMICAL CHARACTERIZATION

Oil/surfactant mixtures have a potential use as vehicles for the admin istration of lipophilic drugs, generally contained in soft gelatin cap sules. This paper examines the viability of incorporating a vegetable oil, corn oil, into hydrosoluble PEG 400/polyoxyethylene 20 cethyl eth er mixtures in order to obtain semi-solid emulsifying bases for eventu al hard gelatin capsule filling. The addition of another surfactant, p olyoxyl 60 hydrogenated castor oil, is necessary to allow the inclusio n of high percentages of oil. Photomicrographic, differential scanning calorimetry and rheologic methods were used to carry out a physico-ch emical investigation of these quaternary mixtures. The results show th at the solubilization grade of polyoxyethylene 20 cethyl ether in the media is the main parameter influencing the stability of the systems a t the temperatures of the study. An excess of surfactant in insolubili zed form leads to the physical instability of quaternary mixtures.