CRYSTAL FORMS OF PIROXICAM PIVALATE - PREPARATION AND CHARACTERIZATION OF 2 POLYMORPHS

This study investigates the polymorphism of piroxicam ester with pival ic acid. Two crystal modifications were prepared by recrystallization from toluene (form 1)and ethyl acetate (form 2). Data regarding prepar ation conditions, solid state properties, and physicochemical characte rization of two polymorphs by means of FT/IR spectroscopy, X-ray diffr actometry on powder, and thermal analysis are reported. Heat of fusion rule and thermodynamic formulas consistently indicate an enantiotropi c stability relationship of forms 1 and 2 with a calculated transition point (32 degrees C) near the ambient temperature. The phase diagrams of each polymorph with piroxicam were also investigated in order to g ain information about the thermal behavior of their solid mixtures. Li quidus curves calculated by the Schroder-Van Laar equation from fusion enthalpies and temperatures were found to agree satisfactorily with e xperimental results obtained by first heating runs with differential s canning calorimetry.