From the Guidelines
For contrast allergy prevention, a premedication regimen typically includes corticosteroids and antihistamines, with the standard protocol being oral prednisone 50 mg at 13 hours, 7 hours, and 1 hour before the procedure, along with diphenhydramine (Benadryl) 50 mg orally or intravenously 1 hour before the procedure, as supported by the most recent evidence 1.
Key Considerations
- The incidence of anaphylactoid reactions to contrast media is low, around 1%, with severe reactions occurring in approximately 0.04% of cases 1.
- A history of seafood or shellfish allergy does not increase the risk of anaphylactoid reaction to contrast media, as iodine does not mediate these reactions 1.
- Premedication with corticosteroids and antihistamines can reduce the risk of recurrent anaphylactoid reactions in patients with a prior history of such reactions 1.
Medication Regimens
- For patients who can complete the 13-hour protocol, oral prednisone 50 mg at 13 hours, 7 hours, and 1 hour before the procedure, along with diphenhydramine 50 mg orally or intravenously 1 hour before the procedure, is recommended 1.
- For urgent cases, an accelerated regimen of methylprednisolone 40 mg IV every 4 hours until the procedure, plus diphenhydramine 50 mg just before the procedure, may be used 1.
- Adding famotidine 20 mg (an H2 blocker) may provide additional protection for patients with severe previous reactions, although the evidence for this is not as strong 1.
Patient Education
- Patients should inform their healthcare providers about any medication allergies, especially to corticosteroids or antihistamines, before receiving this premedication regimen 1.
- The risk of biphasic reactions and the importance of having self-injectable epinephrine available should be discussed with patients, particularly those with a history of severe anaphylaxis 1.
From the Research
Medications for Contrast Allergy
- Corticosteroids and anti-histamines are commonly used as premedication to prevent contrast reactions 2, 3
- Rapid desensitization to iodinated contrast media can be achieved by administering progressively incremental doses of the media 2
- Antihistamine and steroid premedication can be given to patients with a history of hypersensitivity reaction to iodinated contrast medium 4
- Gadolinium-based contrast agents can be employed as an alternative to iodinated contrast medium in patients with a history of hypersensitivity reaction 4
Administration and Timing
- The median time from premedication to contrast was 24 minutes (interquartile range, 0-36 minutes) in one study 5
- Premedication can be administered en route to (or in) the neuroangiography suite 5
- Re-exposition or drug provocation test should only be done with skin test-negative ICMs, and the decision for performing either test needs to be taken based on a risk-benefit analysis 6
Patient Management
- Patients with a history of hypersensitivity reaction to iodinated contrast medium should be observed adequately and followed for the possibility of late reactions 4
- Appropriate drugs and resuscitation equipment should be immediately available for patients with a history of hypersensitivity reaction to iodinated contrast medium 4
- Skin tests are recommended as the initial step for diagnosing patients with immediate and nonimmediate hypersensitivity reactions 6