Synthesis and characterization of iodixanol.

Iodixanol (Visipaque) is a new nonionic roentgen contrast medium intended for general use. Visipaque is a pharmaceutical formulation of iodixanol which is isotonic and iso-osmotic with blood. Two synthetic routes from 5-nitro-isophthalic acid to iodixanol are described. The chemical structure is confirmed by spectroscopical data (1H-NMR, 13C-NMR, FAB-MS, electrospray-MS, UV, IR and Raman). Chromatographic characteristics are related to the isomerism of iodixanol.