Objective: To study the crystalline form of levofloxacin lactate. Methods: The preparation of the crystalline levofloxacin lactate was carried out by means of cooling crystallization,anti-solvent precipitation and the crystal form transformation at high temperature condition. The obtained sample had been analyzed by using single crystal X-ray diffraction (SXRD),powder X-ray diffraction (PXRD),thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Results: Levofloxacin lactate has at least two different crystal forms at ambient conditions,named as form Ⅰ and form Ⅱ. The main differences between two polymorphic forms are the contents of crystalline water in the structures. The form Ⅰ belongs to monohydrate,whereas form Ⅱ belongs to hemihydrate,and the PXRD and TGA-DSC could be used to identify two different forms effectively. Moreover, form Ⅱ can easily convert to form Ⅰ at 25℃ and 90%±5% relative humidity,and form Ⅰ was stable under 60℃. Conclusion: There are polymorphic forms of levofloxacin lactate,and form Ⅰ is more suitable for a commercialized solid state.
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