From the Guidelines
For patients with a history of contrast-induced allergy, the recommended pre-contrast prednisone dosing is 50 mg administered 13 hours, 7 hours, and 1 hour before the procedure, in conjunction with 50 mg of diphenhydramine 1 hour before the procedure, as this regimen has been shown to reduce the risk of recurrent anaphylactoid reactions to close to zero 1. This recommendation is based on the evidence that adequate pretreatment of patients with prior anaphylactoid reactions significantly reduces the recurrence rate of such reactions.
- The incidence of anaphylactoid reactions to contrast media is relatively low, at 1%, with severe reactions occurring in as low as 0.04% of cases 1.
- However, for patients with a history of prior anaphylactoid reaction, the recurrence rate without prophylaxis can range from 16% to 44% 1.
- A regimen of prednisone and diphenhydramine has been demonstrated to effectively reduce this risk, with the specific dosing of prednisone being critical for maximizing the preventive effect 1.
- It's also worth noting that a common misconception about cross-reactions between seafood or shellfish allergies and contrast media reactions due to iodine has been debunked, and pretreatment based solely on such allergies is not recommended due to the potential for adverse effects without demonstrated benefit 1.
- In practice, a simplified regimen of 60 mg of prednisone the night before and morning of the procedure, along with 50 mg of diphenhydramine 1 hour before the procedure, is often used, although the evidence specifically supports the three-dose prednisone regimen 1.
From the Research
Recommended Pre-Contrast Prednisone Dosing
- The recommended pre-contrast prednisone dosing in patients with a history of contrast-induced allergy is not explicitly stated in a single standard dose across all studies, but various regimens have been explored:
- A study from 1984 2 used prednisone 50 mg, 13 hours, 7 hours, and 1 hour before the procedure.
- A 1991 study 3 compared regimens including 50 mg of oral prednisone 13,7, and 1 hour before procedures.
- A 2020 study 4 used prednisone (20 mg or 50 mg, randomly assigned) 13,7, and 1 hour before the iodinated contrast media administration, finding no significant difference in efficacy between the two doses.
Efficacy of Premedication
- Premedication with corticosteroids, such as prednisone, and antihistamines has been shown to reduce the risk of allergic-like reactions to iodinated contrast media in high-risk patients 2, 4, 3, 5.
- The efficacy of premedication can vary, with some studies indicating a significant reduction in reaction rates 2, 5, while others show that despite premedication, some patients still experience reactions 4, 5.