So oleic acid was chosen as oil for the preparation of the microemulsions containing STZL. In two usedsurfactants, STZL had a higher solubility in Tween 80 (47 mg/ml)than Cremophor-EL (36.5 mg/ml). Among two co-surfactants thesolubility of STZL in Propylene glycol (28.4 mg/ml) was more thanpropanolol (17.2 mg/ml)