The need for improved contrast media. Ioxilan: updating design theory.

Because of computed tomography (CT) and digital subtraction angiography (DSA), other diagnostic procedures assisted by urovascular contrast media (CM) have decreased, but the annual total remains at 10 to 11 million procedures since 1980. This trend, expected to continue, suggests that CM will remain vital to medical imaging. The current nonionic CM are not universally affordable, and may elicit pain in peripheral angiography. The author and co-workers explored conversion of ionic into nonionic CM, and have arrived at Ioxilan, 5-(N-2,3-dihydroxypropylacetamido)-2,4,6-triiodo-N-(2-hydroxyethyl )-N'-(2,3- dihydroxypropyl)-isophthalamide; a stable, water-soluble and well-tolerated CM. Ioxilan has unexpectedly low osmolality (570 mOsm at 300 mgI/mL), attributable to the region of double-methylenes that, by hydrophobic bonding, transiently associates the Ioxilan molecules. The high overall hydrophilicity, and thus good biological tolerance, of Ioxilan is accomplished by masking the hydrophobic region with a hydrophilic group. The author suggests that improved urovascular nonionic CM can be designed using this principle.