Anaphylactoid reactions to iodinated contrast material.

A review of the literature involving anaphylactoid reactions to iodinated contrast material (ICM) suggests that the reactions are nonantibody-mediated but that a complex activation of inflammatory mediators occurs. Histamine release and/or complement activation has been demonstrated in both in vitro and in vivo experimental systems. It appears that pretreatment of selected cases (those patients previously exhibiting an anaphylactoid reaction) is effective in reducing the frequency and severity of subsequent reactions when readministration is necessary.