RATIONALE AND OBJECTIVES. Nearly 40 years ago, investigators began collecting data regarding idiosyncratic reactions to iodinated contrast agents. The rates of idiosyncratic reactions in patients receiving ionic contrast agents are compared with those found in patients receiving nonionic agents.
METHODS. A comprehensive literature review was conducted. Retrospective and prospective studies were included, as well as recent analytical multistudy reviews.
RESULTS. For conventional hypermolar agents, rates are estimated to be 5% and the rate of repeat reactions, greater than 20%. Large comparative studies conducted in the late 1980s found significantly lower rates of idiosyncratic reactions with the newer, nonionic agents than with conventional agents. The results of studies evaluating the use of routine administration of steroids before the use of ionic agents have been contradictory. Two analytical reviews of earlier research find fault with the methodology of most studies, but the reviewers supported the increased safety of nonionic agents.
CONCLUSIONS. All iodinated contrast media have excellent safety records. Most evidence, however, demonstrates that nonionic agents are safer than ionic agents.