title: Crystal forms of piroxicam pivalate: preparation and characterization of two polymorphs.
abstract: This study investigates the polymorphism of piroxicam ester with pivalic acid. Two crystal modifications were prepared by recrystallization from toluene (form 1) and ethyl acetate (form 2). Data regarding preparation conditions, solid state properties, and physicochemical characterization of two polymorphs by means of FT/IR spectroscopy, X-ray diffractometry on powder, and thermal analysis are reported. Heat of fusion rule and thermodynamic formulas consistently indicate an enantiotropic 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 gain information about the thermal behavior of their solid mixtures. Liquidus curves calculated by the Schröder-Van Laar equation from fusion enthalpies and temperatures were found to agree satisfactorily with experimental results obtained by first heating runs with differential scanning calorimetry.
authors.affiliation: Dipartimento Farmaceutico, University of Parma, Italy. giordano@ipruniv.cce.unipr.it
authors.forename: F
authors.initials: F
authors.lastname: Giordano
authors.forename: A
authors.initials: A
authors.lastname: Gazzaniga
authors.forename: J R
authors.initials: JR
authors.lastname: Moyano
authors.forename: P
authors.initials: P
authors.lastname: Ventura
authors.forename: M
authors.initials: M
authors.lastname: Zanol
authors.forename: T
authors.initials: T
authors.lastname: Peveri
authors.forename: L
authors.initials: L
authors.lastname: Carima
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000138:chemical synthesis / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D018360:Crystallography, X-Ray; D010421:Pentanoic Acids / Q000737:chemistry; D010894:Piroxicam / Q000138:chemical synthesis / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013237:Stereoisomerism; D013816:Thermodynamics
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D010421:Pentanoic Acids; D010894:Piroxicam; C005566:pivalic acid