A 45-year-old man with a documented moderate urticarial reaction to iodinated contrast requires a contrast-enhanced CT for staging of colorectal cancer. According to the ACR premedication protocol, the recommended oral corticosteroid regimen is:
- A Prednisone 50 mg at 13 hours, 7 hours and 1 hour before the scan, with diphenhydramine 50 mg 1 hour before ✓
- B Hydrocortisone 200 mg IV immediately before contrast injection
- C Prednisone 100 mg single dose 1 hour before the scan
- D Methylprednisolone 500 mg IV daily for 3 days before the scan
Correct answer: A. Prednisone 50 mg at 13 hours, 7 hours and 1 hour before the scan, with diphenhydramine 50 mg 1 hour before
Explanation
The standard ACR (Greenberger) premedication protocol is prednisone 50 mg orally at 13, 7 and 1 hour before contrast, combined with diphenhydramine 50 mg 1 hour before. A single immediate dose of steroid provides no protection because corticosteroids require several hours to suppress the inflammatory cascade, which is why emergency scans cannot be adequately premedicated. Indian practice commonly substitutes prednisolone 40 mg at the same time points.
Reference: ACR Manual on Contrast Media, 2023 ed.
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Written and medically reviewed by the StethoPrep medical team.