The Safety of Contrast Agents
At the time of diagnosis and in the setting of possible breakthrough disease, MRIs done with contrast help distinguish new disease activity from old scars or healed lesions. Recently, the FDA investigated contrast dyes to assess whether they pose any danger to patients.
For many years, contrast agents for MRI based on gadolinium were believed to be safe for anyone with normal kidney function. The FDA has since found that contrast agents can be retained in the body for long periods of time, leading the FDA to include warnings on gadolinium agents. Whether retaining gadolinium in the body causes any specific harm, however, has yet to be determined. As noted in the CMSC’s 2018 Revised MRI Guidelines, gadolinium-based contrast agents “should be used judiciously, recognizing that gadolinium continues to play an invaluable role in specific circumstances related to the diagnosis and follow-up of individuals with MS.”
Although this information may appear contradictory, neurologists and radiologists must take many factors into consideration when deciding whether or not to use gadolinium-based contrast agents, based on benefits and risks. In some instances, when evaluating MS-disease activity in the brain and spinal cord, the benefits of using these contrast agents outweigh the undetermined risk of the agents being retained in the body for a longer period of time. Without contrast agents, evidence of current disease activity often cannot be viewed on the scans.
Certain gadolinium preparations appear to have a higher risk of being retained in the body than others. For the FDA’s report, please visit https://www.fda.gov/Drugs/DrugSafety/ucm589213.htm.
Another potential safety concern with having an MRI with gadolinium is the possibility of being allergic to this contrast agent. According to an article in the August 2012 issue of Radiology, “Immediate Hypersensitivity Reaction to Gadolinium-based MR Contrast Media” (Jung JW, et al. 264:2, 414-422), only a very small percentage of individuals experience an immediate reaction to gadolinium contrast agents for magnetic resonance. This was according to a study of nearly 85,000 patients where only 102 patients (0.121 percent) experienced a reaction. This figure is roughly 12 people out of every 10,000 receiving gadolinium as a contrast agent.
Of this small percentage of people, researchers found that having an initial reaction is more common in women and in those with allergies and asthma. Additionally, the recurrence of a reaction occurs in 30 percent of those who previously had a reaction. For this reason, appropriate premedication with an antihistamine or systemic corticosteroid should be considered for anyone who previously experienced a reaction. Hives were the most common reaction and occurred in 91.1 percent of those who experienced an allergic reaction. Anaphylaxis (severe allergic reaction) was less common and occurred in 9.8 percent of those having any allergic reaction to the contrast.