RATIONALE AND OBJECTIVES: Osmolality, including "dynamic osmolality," which is observed during dilution in the plasma, viscosity, density, and partition coefficient of 11 commercially available contrast media and two new nonionic monomers were determined. METHODS: Osmolality was measured by vapor pressure osmometry, viscosity by determining flow in microcapillaries, and partition coefficient in n-octanol or n-butanol/water mixtures by inductively coupled plasma mass spectroscopy or x-ray fluorescence analysis of iodine concentrations. RESULTS: For the commercially available contrast media, the following statistically significant ranking of osmolality was obtained at 300 mg iodine/mL: iotrolan << ioxaglate < iopromide < iopamidol < ioversol = iohexol < iopentol << meglumine diatrizoate. The novel nonionic monomers, ZK 119095 and ZK 139129, had very low osmolalities, and ZK 139129 was isotonic to blood. The partition coefficient for the system n-octanol/water was lowest for the ionic compounds ioxaglate and diatrizoate followed by the nonionic dimer iotrolan. In n-butanol, iotrolan showed the lowest partition coefficient. CONCLUSION: "Dynamic osmolalities" of contrast media may differ from static values possibly because of the formation of "quasi-oligomers." Especially for ZK 139129, disaggregation occurred during dilution and the osmolality increased slightly. However, osmolality was lower than for any other monomer during the whole dilution process.
RATIONALE AND OBJECTIVES: Osmolality, including "dynamic osmolality," which is observed during dilution in the plasma, viscosity, density, and partition coefficient of 11 commercially available contrast media and two new nonionic monomers were determined. METHODS: Osmolality was measured by vapor pressure osmometry, viscosity by determining flow in microcapillaries, and partition coefficient in n-octanol or n-butanol/water mixtures by inductively coupled plasma mass spectroscopy or x-ray fluorescence analysis of iodine concentrations. RESULTS: For the commercially available contrast media, the following statistically significant ranking of osmolality was obtained at 300 mg iodine/mL: iotrolan << ioxaglate < iopromide < iopamidol < ioversol = iohexol < iopentol << meglumine diatrizoate. The novel nonionic monomers, ZK 119095 and ZK 139129, had very low osmolalities, and ZK 139129 was isotonic to blood. The partition coefficient for the system n-octanol/water was lowest for the ionic compounds ioxaglate and diatrizoate followed by the nonionic dimer iotrolan. In n-butanol, iotrolan showed the lowest partition coefficient. CONCLUSION: "Dynamic osmolalities" of contrast media may differ from static values possibly because of the formation of "quasi-oligomers." Especially for ZK 139129, disaggregation occurred during dilution and the osmolality increased slightly. However, osmolality was lower than for any other monomer during the whole dilution process.