Polymorphism of carbamazepine: solid-state studies on carbamazepine dihydrate
Dugué, J.; Céolin, R.; Rouland, J.C.; Lepage, F.
Pharmaceutica Acta Helvetiae 66(11): 307-310
1991
ISSN/ISBN: 0031-6865 PMID: 1758890 Document Number: 383624
Carbamazepine dihydrate (CBZ.2H2O) crystallizes in the orthorhombic system, space group Cmca or C2ca. The unit-cell constants are: a = 19.834(7), b = 4.945(1), c = 28.826(9) A. M = 272.27, V = 2827(2) A3, Z = 8, D = 1.280 g.cm-3. Indexed X-ray powerder diffraction pattern is given. Dehydration process was studied by means of thermogravimetry and differential thermal analysis: the enthalpy of dehydration was found at 51 kJ per H2O mole. Thermal dehydration leads to an (anhydrous) gamma-form of CBZ when processed in dry atmosphere. The presence of water vapour induces the formation of the beta-form of CBZ as well as the grinding of CBZ.2H2O at room temperature.