WASHINGTON U.S. health regulators remain concerned about the safety of contrast agents used to enhance echocardiogram heart imaging tests, according to Food and Drug Administration documents released on Friday.
The products -- which include Optison, made by General Electric Co's GE Healthcare, and Definity, made by privately-held Lantheus Medical Imaging -- have already been linked to serious heart problems and deaths in some patients.
Four more deaths in patients given the Lantheus product have been reported to the agency since October 2007, according to the documents.
"FDA remains concerned about the accumulating safety data pertaining to marketed ultrasound contrast agents, and the labels for these products continue to contain a boxed warning that highlights the risk for serious cardiopulmonary reactions," agency officials wrote.
Last October, the FDA called for new warnings on the products after it received about 200 reports of serious complications, including seven deaths. Problems included patients whose hearts stopped beating, as well as breathing trouble and seizures.
But the agency scaled back the warnings earlier this year after doctors said some of the information they gleaned from the tests that used contrast agents could be life-saving.
Echocardiograms use ultrasound imaging to take a detailed, moving picture of the heart and help diagnose heart disease and other conditions. If the image is unclear, contrast agents can be given intravenously to help make the heart easier to see.
The FDA documents were released ahead of a public meeting on Tuesday when an independent panel of experts will review the safety of such products.
The FDA said it is currently weighing other experimental contrast agents and wants to familiarize its panelists with the overall issues before it seeks their opinion on the products in the months ahead. The advisers on Tuesday will not discuss possible regulatory action against any specific product, the agency added.
Agency officials also want to explore the risks of such products, which are being tested for other possible uses, including the detection of liver problems, the FDA said.
So far, most of the reported problems with the agents were seen in patients given Lantheus's Definity, because GE did not market its Optison product from November 2005 to October 2007, according to the FDA.
GE Healthcare voluntarily withdrew Optison after an FDA inspection found problems with a contract manufacturer, the company said in separate documents. No serious side effects have been reported since it relaunched Optison last year, GE added. A company review of its safety data "does not indicate a safety concern or risk," officials wrote.
Lantheus officials, in other documents also released by the FDA, said there have been fewer than 300 reports of serious complications and that the number of deaths was small compared to the roughly 2 million doses given since Definity's 2001 launch. The company also said data from recent clinical trials show Definity improves the ability of doctors to make a diagnosis.
Privately-held Bracco Diagnostic Inc, which sells its SonoVue contrast agent in Europe, is also expected to participate in Tuesday's meeting.
Definity was formerly marketed by Bristol-Myers Squibb Co before the drugmaker sold its imaging business to private equity firm Avista Capital Partners earlier this year.
(Editing by Jeffrey Benkoe and John Wallace)