D3.20 - Searching for an Alternative Contrast Agent in a Patient Allergic to Multiple Nonionic Iodinated Contrast Media

Nonionic iodinated contrast media have replaced ionic contrast agents for intravascularadministration due to their lower toxicity risk. Consequently, ionic agents are rarelyconsidered as alternative options in case of hypersensitivity reactions to iodinatedcontrast media

A 67-year-old female patient with a history of stroke developed a disseminated pruriticmicropapular rash 18 hours after receiving iohexol during a CT scan.. A skin biopsywas performed, and a 7-day course of oral corticosteroids and antihistamines wasprescribed, resulting in clinical resolution. The patient reported a similar reaction 25years earlier after the administration of an unidentified iodinated contrast media.Subsequent MRI studies were uneventful.

Skin biopsy: Findings were consistent with a drug reaction (superficial perivascular andinterstitial dermatitis with eosinophils).Skin tests: Prick (1/1) and intradermal (1/10) tests with nonionic iodinated contrastmedia (iohexol, ioversol, iodixanol, iomeprol, iobitridol) were negative at 20 minutes.However, at 24 hours, delayed intense positivity was observed for all agents, exceptiobitridol.Provocation test with iobitridol (100 mL over 4 minutes) was conducted withoutpremedication, showing good immediate tolerance. However, 8 hours later, shedeveloped a disseminated micropapular rash requiring traeatment.Given the diagnosis of delayed hypersensitivity due to sensitization to multiple nonioniciodinated contrast media, we performed skin tests (prick [1/1] and intradermal [1:10])with an ionic iodinated contrast agent (sodium/meglumine amidotrizoate meglumine),yielding negative immediate and delayed readings. Provocation test (50 mL over 4minutes) with this ionic contrast agent without premedication, showed both goodimmediate and delayed tolerance. No renal function abnormalities were observedfollowing the procedure.

Although ionic iodinated contrast media are associated with higher toxicity and are nolonger routinely used for intravascular administration, they may be a viable alternativefor patients with hypersensitivity to nonionic contrast media.

Selecting an alternative contrast media based on allergy testing results is safer thanempirical choice. Without prior testing, another nonionic contrast agent to which thepatient was also sensitized might have been chosen, potentially resulting in an adversereaction.