DEVELOPMENT OF TRETINOIN AQUEOUS GEL FOR TREATMENT OF POSTINFLAMMATORY HYPERPIGMENTATION AND SENILE LENTIGINES

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All-trans retinoic acid(atRA), one of the retinoids, is effective in the treatment for skin hyperpigmentation and acne in dermatology. However, atRA has several drawbacks such as irritation power, poor stability for the air, light and heat, and insoluble water. It is well known that cyclodextrins and their derivatives form inclusion compounds with many kinds of drugs and improve the physicochemical properties of the drugs. The aim of this study was to investigate inclusion compound formation of atRA with hydroxypropyl β-cyclodextrin (HP-β-CD) for solubilization and stabilization of atRA.Inclusion compound was prepared by evaporation of HP-β-CD-atRA ethanol solution at the 1:1 molar ratio. Power X-ray diffractometry, fourier transform infrared spectroscopy(FTIR), differential scanning calorimetry(DSC), solubility test and photostability test were performed to evaluate inclusion compound formation.No diffraction peaks due to atRA crystals were observed on the XRD pattern in the evaporated sample. In the FTIR spectrum, the asymmetric stretching band of the C=C groups in atRA were shifted to higher wavenumber (1600-1604 cm^<-1>). DSC curves of evaporated sample indicated that new endothermic peak at 213.2℃ due to decomposition of HP-β-CD-atRA complex. Aqueous solubility and photostability of atRA in evaporated sample were improved. These results indicated that complexation was occurred between HP-β-CD and atRA in solid and solution.