Investigations into the environmental fate and effects of iopromide (ultravist), a widely used iodinated X-ray contrast medium

Iodinated X-ray contrast media are pharmaceuticals which are biologically inert and metabolically stable during their passage through the body and are excreted almost completely within a day into waste water. They are not readily biodegradable. However, in a test system simulating sewage treatment, we were able to show that the model compound iopromide (N,N′-bis(2,3-dihydroxypropyl)-2,4,6-triiodo-5-methoxyacetylamino-N-methyliso-phthalamide) was amenable to primary degradation. The resulting degradation product (5-amino-N,N′-bis(2,3-dihydroxypropyl)-2,4,6-triiodo-N-methyliso-phthalamide) showed a faster photolysis than the parent compound. Additionally this product was further degraded in a test system simulating surface water conditions. Short-term toxicity of the primary degradation product was low, i.e. no effects on any of various aquatic species could be found even at concentrations of 1 g l−1. Additionally no chronic toxicity of the degradation product was observed in an early-life stage test with zebrafish at the highest tested concentration of 100 mg l−1. Based on the results from model systems a degradation pathway for iopromide is postulated. Though further work showing the transferability of the laboratory results to environmental conditions is necessary the presently available information on the environmental fate and effects of iopromide and its degradation products do not provide evidence of a risk for aquatic life caused by the introduction of this contrast medium into waste water.