Abstract: To improve the water solubility and bioavailability of altrenogest (ALT), sulfobutyl ether-β-cyclodextrin (SBE-β-CD) was used to encapsulate ALT. In this study, the freeze-drying method was used to prepare the inclusion complex of ALT-SBE-β-CD, to solve the problems of limited clinical use of ALT due to its water insolubility and low bioavailability, so as to broaden the medicinal way of ALT. The inclusion complexes were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis and microscopy, and the solubility of the inclusion complex was determined by the solubility method. Taking the yield and inclusion rate of inclusion complex as evaluation indexes, the optimal preparation conditions of inclusion complex were selected. The optimal preparation conditions were as follows:at 55℃, the molar ratio of ALT to SBE-β-CD was 1:6, the inclusion time was 5 h, the pH value of the solution was 8, and the amount of solvent was 15 mL (when the dosage of ALT was 0.1 g). The average inclusion rate of ALT was (90.90±1.80)% (n=3), the average drug loading was (4.30±2.30)% (n=3), and the yield of the inclusion complex was (93.19±1.67)%. By Fourier transform infrared spectroscopy, thermogravimetric analysis and microscope imaging method for characterizing the inclusion complex was prepared by, verifiable inclusion complex was successful, solubility method, the test results show that the formation of inclusion complex, its solubility is ALT technical increased 988.86 times, and the inclusion complex has good stability, can meet the requirements of different dosage forms. SBE-β-CD has a good solubilization effect on the drug, which can increase the solubility of the ALT. The preparation method is simple, the conditions are mild, and it is easy for industrial production, which is conducive to the further development and utilization of the drug.

Key words: altrenogest, sulfobutyl ether-β-cyclodextrin, freeze-drying method, inclusion complexes, characterization