If this is an emergency call 911.
If You Have Had a Contrast Reaction: What you need to know about premedication
This handout is for patients who have had a moderate or severe allergic reaction when they received contrast in the past, who are scheduled for an imaging study that uses contrast materials. The scans discussed are a computed tomography (CT) scan that uses iodinated contrast (X-ray dye) and a magnetic resonance (MR) scan that uses a gadolinium contrast agent. Premedication is explained as a way to prevent another allergic reaction for most patients.