Neurotoxicity of iohexol: a new nonionic contrast medium

The neurotoxicity of iohexol was evaluated and compared with the neurotoxicity of sodium diatrizoate, meglumine iothalamate, and metrizamide. Direct neurotoxicity was evaluated with in vitro rat hippocampal slices, and angiographic neurotoxicity was studied in a cat's spinal cord following thoracic aortography. In the experiments with the hippocampal slices, the ionic agents, sodium diatrizoate and meglumine iothalamate, and metrizamide caused early excitatory changes in electrical activity and later inhibition, but iohexol caused only inhibition. In the experiments with the cat's spinal cord, the ionic contrast materials produced an increase in the ventral root reflexes, and iohexol and metrizamide produced no significant effect. These results indicate that iohexol is less neurotoxic than metrizamide and the ionic contrast materials and may be a very useful angiographic and/or myelographic contrast agent.