A prospective trial of ionic vs nonionic contrast agents in routine clinical practice: comparison of adverse effects.

A multicenter study of adverse effects of ionic and nonionic contrast agents was conducted in three similar time periods. In 1985, before approval of the nonionic contrast agents by the Food and Drug Administration, 6006 consecutive patients received iv ionic agents for urography or CT. After approval of the nonionic agents, 7170 consecutive patients referred for the same examinations were studied. The two groups of patients were significantly different, but the differences were small and did not uniformly favor either group. The incidence of adverse effects in the patients given ionic contrast material was significantly higher than that of the nonionic group (4.17% vs 0.69%, p less than .001). The reactions were also more severe in the ionic group than in the nonionic group (p less than .005). A patient questionnaire disclosed that many patients did not feel well for hours to days after the procedure and also did not immediately resume normal activities of daily living. The nonionic agent was significantly less distressful than the ionic agent. We conclude that nonionic agents cause fewer and less severe adverse effects. Reducing adverse effects can save the patient or the examining site either time or money. However, this study does not show that nonionic agents are more cost-effective than ionic agents.