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Switching Contrast Media Reduces Allergic Reactions Better Than Steroid Pre-Medication


Patients who switch contrast media prior to a CT scan have fewer allergic reactions than do those treated with steroid pre-medication.

If you’ve been a radiologist long enough, you’ve seen a patient have a reaction to contrast media. Depending on the severity, it can be scary for both you and the patient, and the possibility of these events has led to steroid pre-medication in high-risk patients.

That protocol could change for patients who have had previous acute allergic reactions.

In a study published Aug. 3 in Radiology, a team of investigators, led by Robert J. McDonald, M.D., Ph.D., assistant professor of radiology at the Mayo Clinic, share their findings that point to the potential inefficacy of giving patients corticosteroids prior to contrast-enhanced CT exams.

“In this cohort, using iodinated contrast media (ICM) substitutions was more effective for preventing repeat allergic-like reactions than using steroid pre-medication and the same ICM that caused the previous reaction,” the team wrote.

Contrast-enhanced CTs are common in the United States. In 2019 alone, there were 70 million ICM-enhanced scans completed. And, to date, there have been 1 billion doses administered worldwide. One standard pre-medication procedure involves administering oral methylprednisolone at 12-hours and 2-hours before the procedure.

Acute allergic reactions are rare – occurring at a rate of 0.6 percent – but they’re still common enough that they happen daily at major medical centers.

Determining the efficacy of steroid pre-medication is important, the team said, because once a patient has an acute allergic-like reaction to contrast media, they’re at a higher risk for experiencing the same problem again. They investigated whether using iohexol with patients instead of iopromide made any difference.

For their retrospective study, they identified 1,973 adult and pediatric patients who were high-risk for an allergic reaction who had a contrast-enhanced CT scan at their institution between June 1, 2009, and May, 9, 2017. Among the group, they identified 4,360 ICM-enhanced scan that resulted in 280 allergic reactions (6 percent) in 224 patients (11.2 percent). Overall, 9 percent of the reactions were severe.

Hives, itching, and rash accounted for 74 percent of reactions, followed by wheezing and shortness-of-breath (11 percent), and nasal and eye symptoms (7 percent).

After adjusting, the team determined that patients who received a different ICM with or without steroid pre-medication had a significantly lower rate of repeated reaction than did patients who received the same pre-medication (80 out of 423 exams – 19 percent). When patients received a different ICM, but no steroid pre-medication, the reaction rate was 10 out of 322 – 3 percent. It was also 3 percent for patients who received a different ICM with steroid pre-medication (5 out of 166).

Focusing on first scans only, the reaction rate was the same between those receiving pre-medication and those who did not, 26 percent and 25 percent, respectively.

These results, they said, do not fall in line with current procedures.

“The study findings do not support the efficacy of steroid pre-medication (oral methylprednisolone at 12 and 2 hours) for preventing repeat allergic-like reactions in high-risk patients,” they concluded.

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