UPDATE 2-Greater risks seen with certain imaging agents -FDA

* Review found more risk with GE, Bayer, Covidien products

* Off-label use, other issues confound risk assessment

* Companies mixed on how warnings should be applied

* FDA's outside advisors meet Dec 8 to weigh products (Adds FDA and company comments, background)

By Susan Heavey

WASHINGTON, Nov 25 (Reuters) - A U.S. Food and Drug Administration review found the risk of a serious skin disorder is greater with MRI imaging contrast agents made by GE Healthcare, Bayer AG's (BAYGn.DE: 行情) and Covidien (COV.N: 行情), according to an agency memo released on Wednesday.

The review recommended that labels for the products -- GE Healthcare's Omniscan, Bayer AG's (BAYGn.DE: 行情) Magnevist and Covidien's (COV.N: 行情) Optimark -- recognize their greater risk for the potentially fatal disorder over rival agents, it said.

FDA officials released the memo ahead of a Dec. 8 meeting to discuss the risks with all gadolinium-based contrast agents, which already carry a "black-box" warning about the increased potential for the condition in patients with kidney problems.

But the agency is weighing whether the label warnings should be product-specific. It plans to seek advice from its panel of outside experts at the meeting, it said in the memo.

Gadolinium-based contrast agents (GBCAs) are injected in patients undergoing magnetic resonance imaging (MRI) scans to help make the resulting images easier to see and interpret.

The FDA ordered the class-wide warning in 2007, noting that the disorder, called nephrogenic systemic fibrosis (NSF), thickens the skin and other tissues and can inhibit movement. It also called on companies to study the issue.

In Wednesday's memo, the FDA said its review linked GE's Omniscan to the most reports of NSF. The disorder was also reported with other agents, it said, but other issues such as off-label use made it difficult to assess the risk for each product.

GE Healthcare, a unit of General Electric Co (GE.N: 行情), said the class-wide label warnings "have contributed to a dramatic reduction in the occurrence of NSF in patients receiving" the agents. But it disputed the notion that certain products are worse than others.

"There is no definitive evidence establishing that the risk of acquiring NSF is greater for one agent than for the others in the class," it said in a separate document also released on Wednesday.

Other agents include Bayer's Eovist, Bracco Diagnostics' Multihance and Prohance, and Lantheus Medical Imaging's Ablavar, formerly known as Vasovist.

Bayer, in separate documents released by the FDA, said many of the reported NSF cases in patients who received Magnevist were incomplete. It added that the potential for Magnevist and its other agent, Eovist, to be linked to NSF was lower than with other certain rivals.

"Eovist has, to date, demonstrated a favorable efficacy and safety profile in clinical studies and during post-marketing surveillance with a comparable spectrum of reported adverse drug reactions to that known for other GBCAs," it wrote.

Earlier this month, Covidien said it would voluntarily tell doctors and patients that Optimark should not be used in patients with severe kidney problems and would immediately note the change on the product's label.

In a company memo on Wednesday, Covidien said medical use has changed since the FDA's first alert, adding that clinicians are better at screening patients for potential kidney trouble and using other imaging scans as necessary.

"Available data clearly demonstrated that the risk of NSF is not limited to Optimark and all GBCAs may be implicated," it wrote. Optimark is made by Covidien's Mallinckrodt Inc.