This information is for people who have had an allergic reaction to contrast dye in the past. It explains how to prevent an allergic reaction to the contrast dye you’ll get during your scan.
About contrast dye
Contrast is a special dye used in imaging scans. It makes the images from the scans clearer and helps your doctors see your organs better.
There are different kinds of contrast. Computed tomography (CT) scans and magnetic resonance imaging (MRI) use different kinds of contrast. Having an allergic reaction to one type of contrast does not mean you’ll need medicine before getting another type of contrast.
You’ve had an allergic reaction to contrast and you’re having a scan that needs the same type of contrast. Because you’ve had an allergic reaction, you’ll need to take a steroid medicine and an antihistamine (AN-tee-HIS-tuh-meen) before your scan. This will help prevent another allergic reaction.
You’re scheduled to have a ______________ scan on __________ (date) at __________ AM | PM.
Preventing an allergic reaction to contrast with medicine
There are different medicines you can take to prevent an allergic reaction to contrast. Your doctor will give you a prescription for the medicine you need.
Here are some medicines used to help prevent an allergic reaction to contrast. Ask your nurse if you have any questions about when to take your medicine.
Prednisone
If your doctor gave you prednisone (PRED-nih-sone), take 3 doses before your scan:
- Take the first dose 13 hours before your scan.
- Take the second dose 7 hours before your scan.
- Take the third dose 1 hour before your scan.
Write down the time you need to take your medicine below.
Take 1 (50 milligram) tablet of prednisone at:
_____ AM | PM (13 hours before your scan) on __________ (date)
_____ AM | PM (7 hours before your scan) on __________ (date)
_____ AM | PM (1 hour before your scan) on __________ (date)
Take 50 milligrams (mg) of diphenhydramine (Benadryl) with your last dose of prednisone 1 hour before your scan. If you’re allergic to Benadryl, or do not want to be drowsy, take 10 mg of cetrizine (Zyrtec) instead.
Methylprednisolone
If your doctor gave you methylprednisolone (MEH-thul-pred-NIH-suh-lone), take 2 doses before your scan:
- Take the first dose 12 hours before your scan.
- Take the second dose 2 hours before your scan.
Write down the time you need to take your medicine below.
Take 1 (32 milligram) tablet of methylprednisolone at:
_____ AM | PM (12 hours before your scan) on __________ (date)
_____ AM | PM (2 hours before your scan) on __________ (date)
You may also need to take 50 mg of diphenhydramine 1 hour before your scan. Your doctor will tell you if you need to do this. If you’re allergic to Benadryl, or do not want to be drowsy, take 10 mg of cetrizine (Zyrtec) instead.
Other medicine
You may need to take more medicine, or a different medicine instead. Follow your doctor’s instructions.
If you have any questions about your premedication plan, call the doctor that ordered your premedication.
Take: __________ at _____ AM | PM, 1 hour before your scan.