WASHINGTON -- Federal health regulators are warning doctors that a class of injectable drugs used in MRI medical imaging scans can cause a rare and sometimes fatal condition in patients with kidney disease.
The Food and Drug Administration said Thursday it is adding its strongest warning label to imaging agents that contain the chemical gadolinium, highlighting the risks when used in patients with kidney problems.
"These label changes are intended to help ensure these drugs are used appropriately," the FDA said in a posting to its website. The warning language will appear in a bolded box at the top of the drugs' labels.
The agency said in a statement that use of the drugs can lead to a rare syndrome that causes hardening of the skin and tissue growth along joints, eyes and internal organs. The ailment, which is sometimes fatal, is called nephrogenic fibrosing dermopathy and has been reported in patients with weakened kidney function.
There is no known treatment for the condition, though kidney transplant appears to slow disease and even reverse it in some cases.
Known as contrast agents, the products are used to improve clarity in medical scans of the heart and other internal organs. The FDA has approved seven such agents since 1988.
While the nephrogenic syndrome has been reported with all seven drugs, the FDA said three have greater risks than the others: Bayer Healthcare's Magnevist, General Electric Healthcare's Omniscan and Covidien's Optimark. The FDA label stresses that these drugs should not be used in patients with kidney disease.
An agency spokeswoman said those three drugs are "chemically more unstable" than the others in the class and "thus more likely to release gadolinium."
Gadolinium is a metal with distinctive magnetic properties that increase its visibility during MRI scans. It is known to be toxic to the liver.
The four other drugs are Prohance and Multihance from Brocco Diagnostics Inc., Bayer's Eovist and Ablavar from Lantheus Medical Imaging.
The new FDA labels for all seven drugs instruct physicians to screen patients for kidney disease before administering the agents. Doctors should also order lab tests for patients who may be at increased risk of reduced kidney function. The FDA said there haven't been any reports of the syndrome in patients with normal kidney function.
There are two non-gadolinium-based imaging agents on the market, though the FDA has approved them only for liver scans.
GE Healthcare said in a statement that the FDA's labeling reinforces physician guidelines that already stress the importance of screening for patients with kidney problems.
The company said MRI contrast agents "continue to be a valuable diagnostic tool with a proven safety record for the overwhelming majority of patients to whom they are prescribed."
Bayer said it will cooperate with regulators and "will make periodic safety reports to the FDA and other regulators."