Nonionic compact dimers: A new generation of isosmolar iodinated contrast media with low viscosity

Rationale and Objectives. The authors evaluated compact dimers, a new class of molecule designed to reduce the osmolality of concentrated solutions of x-ray contrast media without increasing their viscosity. Materials and Methods. Molecular modeling was used to design a new hexaiodo dimeric structure with low viscosity and good shielding of hydrophobic areas. This design ends in the synthesis of different prototypes, the structure of which was characterized by a single bond between two perpendicular rings and the presence of tertiary amides. The validity of this approach was investigated with measurements of physicochemical properties (viscosity, osmolality, logP) and pharmacologic studies (urinary and biliary excretion, intravenous and intracerebral medial lethal dose). Results. Solutions of the compact dimers at a concentration of 350 mg of iodine per milliliter combine osmolalities that are close to that of blood with viscosities at ambient temperature nearly half those of commercially available dimers. Furthermore, these new compounds have a tolerance level comparable with that of currently used nonionic media (intravenous median lethal dose, >17.5 g of iodine per kilogram). Conclusion. The three-dimensional structure of the compact dimers has made it possible to control both physicotoxicity and chemotoxicity by combining isotonicity and low viscosity with good tolerance.