CHARACTERIZATION OF 2 TERFENADINE POLYMORPHS AND A METHANOL SOLVATE - KINETIC-STUDY OF THE THERMAL REARRANGEMENT OF TERFENADINE FROM THE METHANOL SOLVATE TO THE LOWER MELTING POLYMORPH

Terfenadine was crystallized from solutions of the drug in ethanol, acetone, and methanol. Two polymorphic forms and a methanol solvate were obtained and characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetry (TG). Kinetic parameters were determined for a structural change that the methanol solvate went through during the desolvation reaction which was found to be completed by heating. On the basis of the X-ray diffractogram and the DSC scan the desolvated product was identified as the lower melting polymorph.