Solid-state study of polymorphic drugs: carbamazepine

Polymorphs of a compound have solid crystalline phases with different inter nal crystal lattices; in pharmaceuticals, differences due to polymorphism a nd pseudopolymorphism can affect bioavailability and effective clinical use . The aim of this work was to obtain the different polymorphic modification s of the anticonvulsant drug, carbamazepine, and to characterise them by me ans of typical structure-sensitive analytical techniques, such as FT-IR spe ctroscopy, XRPD and DSC. Further investigations were also performed by Hot Stage FT-IR thermomicroscopy, which permitted the visible and spectroscopic characterisation of the polymorphic forms during heating. Our results conf irm the existence of three different polymorphic forms for anhydrous carbam azepine: Form III, the commercial one, Form I, obtained by heating Form III and Form II, crystallised from ethanolic solution. Substantial differences were detected among the polymorphs with regard to solid-state properties. Moreover, Hot Stage FT-IR thermomicroscopy proved its analytical potential to characterise the drug's polymorphism. (C) 2000 Elsevier Science B.V. All rights reserved.