The non-ionic dimers: a new class of contrast agents.

Non-ionic dimers are a new class of iodinated radiological contrast agents. Some physico-chemical and pharmacological properties of three representative compounds are presented. Non-ionic dimers are iso-osmolar with plasma at all iodine concentrations unless diluted with saline and in terms of chemotoxicity they appear to be closely comparable with the established non-ionic monomeric agents. It is shown that the data lend support to the theory that it is the degree of steric hindrance of the hydrophobic iodine atoms by side-chains which determines this chemotoxicity. Areas in which agents of this type may find applications are indicated.