New Media. Pharmacology of nonionic dimers.

Nonionic dimers enable us for the first time to produce highly concentrated, blood isotonic contrast media. If the toxicity of contrast media is dependent on molar quantity, molar concentration, or the motility of small molecules, nonionic dimers could have advantages over the monomeric contrast media. Their higher viscosity is a basic disadvantage. Solutions of the nonionic dimers with an iodine concentration of up to 400 mg/ml often have an osmotic pressure that is lower than that of blood. THe new contrast media are extremely hydrophilic, show no binding to protein, and lead to complement activation only in extremely high concentrations. They do not cause the deformation of the erythrocytes that is known to occur with other contrast media. The LD50 after fast intravenous injection in the rat is higher that with all other known contrast media. In peripheral arteriography, the nonionic dimers are tolerated painlessly by rats, and in carotid angiography they cause as few side effects as metrizamide. The neural tolerance is better than that of metrizamide. In circulatory investigations no drop in blood pressure was found after intravenous injection. Elimination is almost exclusively renal. As with other nonionic contrast media, properties of the dimers that appear to be problematic are formation of supersaturated solutions and nephrotoxicity after extremely high doses.