SOLID-STATE NMR AND IR FOR THE ANALYSIS OF PHARMACEUTICAL SOLIDS - POLYMORPHS OF FOSINOPRIL SODIUM

The two polymorphic modifications of fosinopril sodium have been chara cterized as to their differences in melting behaviour, powder X-ray di ffraction patterns, Fourier transform infrared spectra (FTIR), and sol id-state P-31- and C-13-NMR spectra. The polymorphs were found to be e nantiotropically related based upon melting point, heat of fusion, and solution mediated transformation data. Analysis of the solid-state FT IR and C-13-NMR data indicated that the environment of the acetal side chain of fosinopril sodium differed in two polymorphs, and that there might be cis-trans isomerization about the C-6-N peptide bond. These conformational differences are postulated as the origin of the observe d polymorphism.