Physicochemical and crystal structure analysis of pranlukast pseudo-polymorphs I: Anhydrates and hydrate

Pranlukast (PRS) is a leukotriene receptor antagonist for the treatment of bronchial asthma. Pranlukast is formulated as a hemihydrate (HH) form in the drug product. Here, we report three new anhydrate forms of PRS (AH, form I-III). These polymorphs and PRS HH were characterized by PXRD, TG-DTA, simultaneous PXRD-DSC and vapor sorption analysis. In addition, the crystal structures of HH and AH-I were determined by single crystal X-ray structure analysis for the first time. HH transformed to AH-I, AH-II and AH-III as the temperature was increased from 25°C to 210°C. At 25°C, AH-I transformed to HH at above 5%RH. HH and AH-I possessed similar crystal packing patterns and molecular structures.