Contrast media: the relation of chemical structure, animal toxicity and adverse clinical effects

Chemotoxicity and osmotoxicity of contrast media (CM) are determined by chemical structure. The lower the chemotoxicity and osmotoxicity of the CM, the less animal toxicity and higher clinical tolerance in humans will be achieved. Nonionic monomers such as iohexol and iopamidol in iodine-equivalent concentrations have approximately half the osmolality and therefore half the osmotoxicity of ionic monomers such as diatrizoate, iodamide, iothalamate and metrizoate. Absence of carboxyl groups in nonionic CM, as opposed to the presence of carboxyl groups in ionic CM, results in a lower chemotoxicity in nonionic CM. Similarly, a larger number of hydroxyl groups in nonionic CM than in ionic CM result in a lower chemotoxicity. The lower chemotoxicity of nonionic CM is reflected as a higher subarachnoid and intravenous tolerance both in animals and in the clinical setting.