From the Guidelines
For patients with a known contrast allergy undergoing a CT scan angio, pretreatment with oral corticosteroids and antihistamines is recommended.
Pretreatment Regimen
A typical regimen consists of:
- 50mg of prednisone administered 13 hours and 1 hour prior to the procedure,
- in conjunction with 50mg of diphenhydramine administered 1 hour prior to the procedure 1. Alternatively, 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 1.
Key Considerations
- Patients with a prior history of allergic reactions to shellfish or seafood do not require anaphylactoid prophylaxis for contrast reaction 1.
- The incidence of anaphylactoid reactions to contrast media is low, but adequate pretreatment can reduce the recurrence rate to close to zero 1.
- The use of steroids and antihistamines has been shown to be effective in reducing the risk of recurrent anaphylactoid reaction 1.
From the Research
Pretreatment Regimens for Contrast Media Allergy
The pretreatment for a patient with a contrast media allergy undergoing a computed tomography (CT) scan angiography (angio) typically involves a combination of medications to reduce the risk of an allergic reaction.
- Corticosteroids and antihistamines are commonly used as premedication to prevent allergic reactions to contrast media 2, 3.
- A study published in 1984 found that pretreatment with prednisone plus diphenhydramine or prednisone and diphenhydramine plus ephedrine decreased the reaction rate to 9.0% and 3.1%, respectively, during 657 procedures in 563 patients 3.
- Another study published in 2015 found that the overall breakthrough reaction rates were 1.2% (13/1051) for patients receiving premedication before undergoing CT with IV iodinated low-osmolality contrast material (LOCM) 2.
Rapid Desensitization for Refractory Contrast Allergy
In cases where patients have a severe breakthrough contrast allergy, rapid desensitization to iodinated contrast media may be an effective strategy.
- A case study published in 2018 reported the successful management of a patient with recurrent, severe allergy to contrast media despite standard precautions using a strategy of rapid desensitization to iodinated contrast media 4.
- Another study published in 2020 highlighted the use of a novel desensitization protocol in a patient with a severe breakthrough contrast allergy and unstable angina that allowed for successful percutaneous coronary intervention 5.
Management of Radio-Contrast Allergy
The management of radio-contrast allergy in patients undergoing coronary angiography and intervention requires careful consideration of the patient's medical history and the use of premedication.
- A retrospective study published in 2020 reported the successful completion of coronary angiography and intervention in 11 patients with a prior history of radio-contrast anaphylaxis who were pretreated with intravenous feniramin maleat and methylprednizolone one hour before the procedure 6.
- The study found that two patients had breakthrough radio-contrast induced anaphylaxis, but were successfully treated with additional doses of intravenous methylpredinisolene, salbutamol nebulae, and intravenous adrenalin 6.