The U.S. Food and Drug Administration (FDA) has updated an existing safety alert, warning of Gadolinium-Based Contrast Agent (GBCA) retention in the body after completing an MRI scan.

GBCA is composed of rare earth metals, and most commonly used intravenously in patients requiring an MRI. When the GBCA is injected into the patient, the metals give the physician improved readings and visuals of organs, blood vessels, and tissues during the scan.

One benefit of using GBCA is a potentially improved diagnosis for the patient. The body naturally eliminates most of the GBCA through the kidneys following the MRI, but trace amounts of the injection have remained in some patients, causing concern over its long-term safety.

There are two types of GBCAs, linear and macrocyclic. According to the Pharmacovigilance Risk Assessment Committee (PRAC) of the European Medicines Agency (EMA), "Linear agents have a structure more likely to release gadolinium, which can build up in body tissues macrocyclic agents are more stable and have a much lower propensity to release gadolinium."

Ongoing research currently includes a study on brain retention of GBCAs in rats. As it stands, the FDA has concluded that the benefit of all approved GBCAs "continues to outweigh any potential risks." Interestingly, the residual gadolinium found in areas like the brain has not been directly associated with adverse effects in patients with normal kidney function.

The only known instance of an adverse reaction from gadolinium retention is nephrogenic systemic fibrosis (NSF), a rare condition occurring in a small subgroup of patients with pre-existing kidney failure.

A new patient medication guide explaining the risks associated with GBCAs is now required by FDA officials to give to patients prior to an MRI. The FDA strongly suggests informing your doctor or specialist about any medical conditions prior to receiving a GBCA, including pregnancy and any kidney irregularities.