From the Guidelines
For patients with a history of allergy to IV contrast, a predose protocol of 50 mg of prednisone administered 13 hours, 7 hours, and 1 hour before the procedure, as well as 50 mg of diphenhydramine 1 hour before the procedure, is recommended to reduce the risk of recurrent anaphylactoid reaction. This regimen has been shown to reduce the recurrence rate of anaphylactoid reactions to close to zero 1. In practice, a regimen of 60 mg of prednisone the night before and morning of the procedure, as well as 50 mg of diphenhydramine 1 hour before the procedure, is often used. Some key points to consider when implementing this protocol include:
- The incidence of anaphylactoid reactions to contrast media is 1%, and the incidence of severe reactions may be as low as 0.04% 1.
- Limited data suggest that in patients with a history of prior anaphylactoid reaction, the recurrence rate without prophylaxis is in the range of 16% to 44% 1.
- There are no data to suggest that those patients with seafood or shellfish allergies are at risk for an anaphylactoid reaction from exposure to contrast media 1.
- For urgent situations, an alternative regimen such as IV steroids (eg, 80 mg to 125 mg of methylprednisolone, 100 mg of hydrocortisone sodium succinate), as well as oral or IV diphenhydramine and possible IV cimetidine, may be considered 1.
From the Research
Predose Protocol for IV Contrast in Patients with a History of Allergy to Contrast Media
- The predose protocol for intravenous (IV) contrast in patients with a history of allergy to contrast media typically involves premedication with corticosteroids and anti-histamines to reduce the risk of allergic reactions 2, 3, 4, 5.
- A common premedication regimen includes cetirizine (10 mg) and prednisone (20 mg or 50 mg) administered 13,7, and 1 hour before the IV contrast procedure 3.
- Another premedication regimen involves prednisone (50 mg) administered 13,7, and 1 hour before the procedure, along with diphenhydramine (50 mg) and optionally ephedrine (25 mg) administered 1 hour before the procedure 5.
- The choice of premedication regimen may depend on the severity of the patient's previous allergic reaction and the specific contrast agent being used 4, 6.
- In some cases, rapid desensitization to iodinated contrast media may be necessary for patients with a history of severe allergy to contrast media 2.
- Skin testing with contrast agents may be helpful in identifying an allergic mechanism and selecting alternative agents for future procedures 6.