Protocol for Patients with History of Allergies to Contrast Media
Patients with prior evidence of an anaphylactoid reaction to contrast media should receive premedication with corticosteroids and antihistamines before repeat contrast administration. 1, 2
Standard Premedication Regimen
For non-emergency procedures, use one of these evidence-based protocols:
Option 1 (Preferred):
- Prednisone 50 mg orally at 13 hours, 7 hours, and 1 hour before contrast administration
- Diphenhydramine 50 mg orally or intramuscularly 1 hour before contrast administration 1, 2
Option 2 (Alternative):
- Prednisone 60 mg orally the night before and morning of the procedure
- Diphenhydramine 50 mg orally or intramuscularly 1 hour before contrast administration 1, 2
Emergency Premedication Protocol
When contrast administration cannot be delayed:
- Hydrocortisone 200 mg IV immediately and every 4 hours until procedure completion, OR
- Methylprednisolone 80-125 mg IV
- Diphenhydramine 50 mg IV/IM 1 hour before the procedure 2, 3
Efficacy and Limitations
- Without prophylaxis, recurrence rates of anaphylactoid reactions range from 16% to 44% 1
- Adequate pretreatment reduces recurrence rates to near zero in most cases 1
- However, breakthrough reactions can still occur despite premedication in approximately 14.6% of high-risk patients 4
- Patients with severe previous reactions remain at higher risk (14.3% may experience severe reactions again despite premedication) 4
Important Considerations
Premedication is NOT indicated for patients with seafood or shellfish allergies alone 1, 2
- The common misconception linking seafood allergies and contrast reactions is not evidence-based
- Iodine does not mediate seafood, shellfish, or contrast media reactions
Always have emergency medications and equipment readily available, as breakthrough reactions can occur despite premedication 2, 5
Exercise caution in patients taking beta-blockers, as anaphylactoid reactions may be more difficult to treat in these patients 2
Higher doses of corticosteroids appear to be more effective in preventing recurrent reactions 4
Risk Stratification
The risk of breakthrough reactions correlates with the severity of the initial reaction:
- Patients with previous severe reactions have a higher risk of recurrence (14.3%) despite premedication 4
- Consider using the more comprehensive premedication regimen (Option 1) for patients with previous severe reactions
By following these evidence-based protocols, the risk of recurrent contrast reactions can be significantly reduced, though not completely eliminated. Always be prepared to treat breakthrough reactions.