X-ray contrast media--an overview.

X-ray contrast media are chemically inert drugs which are given intravascularly in very high amounts within a very short time period. Although they are regarded as relatively safe drugs, adverse reactions can occur: these are normally divided into immediate and delayed reactions. The latter appear hours to days after injection. Immediate reactions have been drastically reduced since the introduction of non-ionic monomers and non-ionic dimers. However, the delayed reactions still occur in a frequency of 1-3% in X-ray contrast media exposed patients. The majority of these reactions are mild and manifest as skin eruption, but severe reactions can also occur. Further improvement of the safety of these drugs is only possible with a better understanding of etiologies behind the observed adverse reactions.