ABSTRACT
Distribution behavior of lipophilic drugs in the oil-in-water (O/W) microemulsions was studied. Fluorescence spectra analysis was performed to investigate the effect of the compositions of microemulsions on the fluorescence spectra of armillarisin and ofloxacin which were used as the model drugs. The fluorescence spectra of the model drugs in the microemulsions with various amount of the compositions were compared. The results showed that the armillarisin were both localized in the interfacial film of microemulsion systems with both phenylmethanol and PEG 400 as the co-surfactants, separately. Ofloxacin was localized in the interfacial film of microemulsion systems with Gradamol GTCC as the oil phase, but in the oil pool of microemulsion systems with oleic acid/olive oil (OA/OO) (1:1) as the oil phase. Besides, it was found that the drug would have the tendency to locate in the microenvironment where the composition with the largest solubility to model drug is located, and its actual localized position would be dependent on the amount of this composition. The results indicate that the localized region of lipophilic drug in the O/W microemulsion systems is related with the solubility of the model drug in various compositions.