Stability Test of Dexamethasone in Vanishing Creams of Various pH by High Speed Liquid Chromatography

The stability of dexamethasone (DMS) in vanishing creams of various pH was studied. Vanishing creams containing 1% MDS were exposed to air at 40° and stability of DMS was measured by using high speed liquid chromatography (HSLC). The conditions of HSLC were as follows: model: JASCO FLC-350; detector: UVIDEC-1; wavelength: 239nm; column: HP-01 (copolymer of styrene-divinylbenzene) 4.5×250 mm; mobile phase: MeOH; flow rate: 1 ml/min; pressure: 40kg/cm2 (at room temperature). The extracted DMS was directly injected into the HSLC column and its stability was determined from the peak height of DMS on the chromatogram. It was found that DMS in vanishing creams was unstable under the basic condition and the decomposition product of DMS in vanishing creams was 3, 17-ketosteroid.