Allergy‐like reactions to iodinated contrast agents. A critical analysis

Abstract

Allergy-like reactions may occur following administration of iodinated contrast media (CM), mostly in at-risk patients (patients with history of previous reaction, history of allergy, co-treated with interleukin-2 or beta-blockers, etc.) but remain generally unpredictable. Severe and fatal reactions are very rare events. All categories of CM may induce such reactions, although first generation (high osmolar CM) have been found to induce a higher rate of adverse events than low osmolar CM. However, no differences were found between the two categories of CM with respect to mortality. Delayed reactions can also occur. There are no differences between the various categories of CM except for non-ionic dimers, which are more likely to induce such effect. Numerous clinical studies have evaluated the prophylactic value of drugs (mostly antihistamines and corticosteroids). Results are unclear and highly variable. Any prevention depends upon the mechanism involved. However, the mechanism of CM-induced allergy-like reaction remains disputed. Relatively recent data revived the hypothesis of a type-I hypersensitivity mechanism. Positive skin tests to CM have been reported. However, the affinity of IgE towards CM has been found to be very low in the only study which actually evaluated it. Other pathophysiological mechanisms (involving direct secretory effects on mast cells or basophils, or activation of the complement system associated or not with the plasma contact system) are also much debated. Anaphylaxis and anaphylactoid reactions are, in the end, clinically undistinguishable.

Hypersensitivity Reactions to Contrast Media: Prevalence, Risk Factors and the Role of Skin Tests in Diagnosis – A Cross-Sectional Survey

“…Dahlstrom et al [28 ]reported the rate of adverse reactions to another nonionic monomer, iohexol, to be 0.8%. As nonionic CMs, iohexol, iomeprol and iopromide were the most common CMs in our study, and our current prevalence rate was comparable with the data reported by studies with nonionic CMs [4,6,7,8,9]. However, the past prevalence rate was relatively higher than current reactions to CMs during the 1-year study period (2.92 vs. 0.72%).…”

“…The introduction of nonionic CMs has been associated with reduced adverse reactions to CM administration [4,6,7,8,9]. The overall rate of adverse reactions to iopromide, a nonionic monomer, was reported to be 1.5% in a large-scale surveillance study [4].…”

“…Hypersensitivity reactions after exposure to CMs are classified according to the time interval between CM administration and the first appearance of clinical manifestations as immediate (reaction within 1 h) and nonimmediate reactions (reaction after 1 h). Although the exact mechanism underlying the pathogenesis of CM-induced allergy-like reactions is not completely understood, recent studies indicate that a subset of immediate reactions are likely true IgE-mediated reactions, while most of the nonimmediate skin reactions are most likely caused by T cells [2,7,12,13]. Thus, patients who experience such hypersensitivity reactions are advised to undergo allergologic evaluation, including skin tests.…”

“…The prevalence rate of CM-induced hypersensitivity reactions was first evaluated through phase II and III clinical trials and then through large-scale postmarketing surveillance studies [4,5,6]. Since the introduction of nonionic CMs into clinical practice, adverse reactions associated with CM administration have been reported less frequently [5,7,8,9,10]. A large-scale nationwide study in Japan reported that not only the prevalence of all degrees of adverse reactions to CMs but also the prevalence of severe and potentially life-threatening adverse reactions were significantly reduced with nonionic CMs [6].…”

Recurrent Flexural Exanthema (SDRIFE or Baboon Syndrome) after Administration of Two Different Iodinated Radio Contrast Media

“…Finally, as it has been earlier reported for immediate [16, 17] and delayed reactions from RCM [7, 8], premedication with corticosteroids and antihistamines is not always protective in delayed as well as immediate reactions from RCM.…”