The FDA has issued a drug safety communication about gadolinium-based contrast agents used in MRIs. It is requiring a new class warning and other safety measures for these products.
Gadolinium-based contrast agents are usually cleared from the body through the kidneys, but trace amounts appear to remain in the body for months to years after its use in patients undergoing MRIs. Retention has not been linked to any adverse health effects in patients who have normal kidney function. The only known adverse health effect related to gadolinium retention is a rare condition called nephrogenic systemic fibrosis that occurs in patients with pre-existing kidney failure. The FDA has received reports of adverse events involving multiple organ systems in patients with normal kidney function, but a causal association between these events and gadolinium retention could not be established.
There are two types of gadolinium-based contrast agents: linear and macrocyclic. Linear agents result in more retention of gadolinium and retention for a longer time than macrocyclic agents. Health-care professionals should consider the retention characteristics of these contrast agent when choosing one for patients who may be at higher risk for gadolinium retention, including patients who require multiple lifetime doses, pregnant women, children, and patients with inflammatory conditions.
The benefits of gadolinium-based contract agents still outweighs the risk of adverse reactions, according to the FDA. Repeated imaging studies with these agents should be minimized when possible, but necessary MRIs should not be avoided or deferred, according to the FDA.
The agency will require several actions to alert health-care professionals and patients about gadolinium retention after an MRI using a contrast agent with gadolinium, and actions that can help minimize problems. These include requiring a new patient medication guide and providing educational information that all patients will be asked to read before receiving a gadolinium contract agent. FDA will also require manufacturers of these contract agents to conduct human and animal studies to further assess their safety.