BY SARAH OWENS
The US Food and Drug Administration (FDA) announced last Tuesday that it will require that gadolinium-based contrast agents (GBCAs) used in MRI scans carry a class warning about their potential to stay in patients' brains and bodies for months or years.
Previous reports have found, for example, that repeated administration of MRI gadolinium-based contrast-agents have been associated with high signal intensity intensity in the cerebellar structures, particularly the dentate nucleus and globus pallidus, of patients with multiple sclerosis.
The FDA's decision was based on a review of available evidence and consultation with its Medical Imaging Drugs Advisory Committee. The FDA's review confirmed that the benefits of gadolinium-based contrast agents outweigh the potential risks, but it advised health care professionals to "consider the retention characteristics of each agent when choosing a GBCA for patients who may be at higher risk for gadolinium retention."
Gadolinium-based contrast agents, which contain the heavy metal, gadolinium, are injected into the vein to enhance visualization of the internal organs, blood vessels, and tissues during MRI scans. They are mostly eliminated from the body through the kidneys and excreted in urine after they are administered to patients.
However, trace amounts of the metal have been found to remain in the brain and body for months or years after administration. In rare cases, GBCAs have been associated with nephrogenic systemic fibrosis, a serious condition that involves scaling and hardening of the skin and may lead to fibrosis of the internal organs, in certain patients with kidney dysfunction.
Among various approved gadolinium agents, retention has been found to be highest for gadodiamide (Omniscan) and gadoversetamide (OptiMARK); less high for gadoxetate disodium (Eovist), gadopentetate dimeglumine (Magnevist), and gadobenate dimeglumine (MultiHance); and lowest for gadoterate meglumine (Dotarem), gadobutrol (Gadavist), and gadoteridol (ProHance).
Approved gadolinium-based contrast agents remain generally safe and beneficial, and doctors should not avoid or put off GBCA MRI scans they deem necessary, the FDA's statement emphasized. For patients who may be at higher risk of retention, including those who are expected to require multiple doses over the course of a lifetime in order to monitor a chronic condition; pregnant women; children; and patients with inflammatory conditions or kidney dysfunction, doctors should strive to avoid repeated imaging studies that use the gadolinium agents.
The FDA will also issue a medication guide that explains the risks associated with the gadolinium-based agents, and advise that all patients undergoing MRI using these agents read the guide prior to the scan. Doctors should also report adverse events or side effects related to the agents to the FDA's MedWatch Safety Information and Adverse Event Reporting Program at www.fda.gov/MedWatch/report.