Polymorphism of phenylbutazone: properties and compressional behavior of crystals.

Data from X-ray diffraction, thermal analysis, IR spectroscopy, and solubility studies were used for the identification and characterization of four crystalline modifications of phenylbutazone. The thermal behavior of the polymorphs under different treatment conditions also was investigated. Compression of the thermodynamically unstable forms, at a compression force of 1590--2040 kg, induced polymorphic changes in the crystals. Similar changes also were produced through grinding. The apparent equilibrium solubilties of polymorphs were determined, as was the dissolution of the polymorphs as compressed disks in an aqueous medium. The small effective surface area possessed by one polymorph resulted in slow dissolution.