[Current problems with delayed reactions to intravascular administration of nonionic contrast media].

Administration of X-ray contrast media is essential in many radiologic procedures such as angiography, computed, tomography, and many other diagnostic methods. These substances have become made more tolerable since the introduction of the first water-soluble X-ray media. Adverse drug reactions decreased by the factor 4 with the development of nonionic contrast media compared to the elder ionic substances. At the same time, a shift to more frequent delayed reactions occurred. Currently the dimeric contrast media for intravascular use are suspected of causing frequent delayed side effects, especially with rashes and other cutaneous symptoms. In this paper, the reasons for adverse reactions independent of drug administration, are discussed. Causes related to patients and geographic differences are reviewed. Summing up, it may be said that the new dimeric contrast media are well tolerated drugs. A higher incidence of adverse drug reactions is not evident from scientific studies. A shift to more delayed side effects, especially, reactions is possible. The mechanism is still unclear. Additionally a classification of the time of incidence of side effects is proposed.