Two New Polymorphic Cocrystals of Zafirlukast: Preparation, Crystal Structure, and Stability Relations

Two
new cocrystals of zafirlukast with piperazine, existing in
five different solid forms, have been discovered during a cocrystal
screening. The crystal structure of one of these forms has been determined
by single crystal X-ray diffraction, and the stability landscape of
the crystalline forms of the new cocrystal has been studied. In the
present article, we extend the knowledge about the solid state of
this important pharmaceutical drug for the treatment of asthma by
reporting the crystal structures of two new solvates (acetonitrile
and butanol) and the elusive anhydrous Form X, which have been solved
by single crystal X-ray diffraction.