Extensive idiosyncratic allergic reaction to non-ionic, low osmolar small dose contrast in a patient premedicated with antihistamine and steroids.

To cite: Vasavada A, Agrawal N, Parekh P, et al. BMJ Case Rep Published online: [please include Day Month Year] doi:10.1136/ bcr-2014-205323 DESCRIPTION Allergic response to iodinated contrast agents is a rare occurrence and is even rarer in non-ionic and low osmolar contrast agents. We present an interesting case of an elderly hypertensive man with New York Heart Association (NYHA) class III angina and dyspnoea with no history of allergy. The patient was taken for a diagnostic angiogram during which he was administered 10–15 mL of non-ionic low osmolality contrast agent iohexol (320–330 mosm). The patient developed rashes all over his body within 1 min of administration of the contrast (figures 1– 4). The patient had been premedicated with Avil (pheniramine maleate) and hydrocortisone, which is a part of our usual protocol in all patients. The patient had no evidence of laryngeal oedema and was managed with another dose of steroids and Avil after which his rashes subsided within minutes. The patient had multivessel coronary artery disease and was given the option of coronary artery bypass grafting or multivessel percutaneous coronary intervention. In various studies of moderate-to-severe adverse reactions to non-ionic iodinated contrast media (ICM), the incidence was much less than 0.1%, while the incidence for ionic ICM was around 0.1%. Similarly, several large studies and meta-analysis have shown a much lower incidence of allergic reactions with low osmolar agents (0.1–0.2%). 5 Premedication with steroids and antihistaminic are believed to decrease the incidence and severity of allergic reactions. An extensive allergic response to a non-ionic, low osmolar contrast agent in a premedicated patient with no history of prior allergy is extremely rare. Figure 1 Extensive urticarial rashes seen on the arm of the patient.