Iohexol is a nonionic, water-soluble radiographic contrast medium. Organic iodine compounds block x-rays as they pass through the body, thereby allowing body structures containing iodine to be delineated in contrast to those structures that do not contain iodine. It is used in myelography, arthrography, nephroangiography, arteriography, and other radiographic procedures. Drugs which lower seizure threshold, especially phenothiazine derivatives including those used for their antihistaminic or antinauseant properties, are not recommended for use with Iohexol. Others include monoamine oxidase (MAO) inhibitors, tricyclic antidepressants, CNS stimulants, psychoactive drugs described as analeptics, major tranquilizers, or antipsychotic drugs. The most frequently reported adverse reactions are headache, mild to moderate pain including backache, neckache and stiffness, nausea, and vomiting.

Metrizamide is a glucosamine derivative of metrazoic acid, used as a contrast medium for myelography. Metrizamide is no longer marketed in the US.