‘Polymorphism’ in a novel anti-viral agent: Lamivudine

Abstract

Two modifications of Lamivudine have been studied. One has a highly symmetrical crystal lattice and the other, unusually, an asymmetric unit containing five non-equivalent molecules (with some disorder). The latter contains one molecule of water for every five of Lamivudine. Solid-state NMR spectra reflect these dramatic differences and the technique has been used to predict the extent of the asymmetry in the latter form. X-Ray diffraction studies confirm the differences in symmetry between the two polymorphs, which have also been characterised by IR spectroscopy and differential scanning calorimetry.