UPDATE 1-Gallstones seen with Roche weight drug-FDA staff

(Adds details on cases reported to FDA, background)

WASHINGTON, April 10 (Reuters) - A review of Roche AG's Xenical has prompted concerns about a possible link between the weight-loss drug and gallstones in patients of all ages, U.S. regulatory staff said in a memo released on Tuesday.

Thirty-seven U.S. cases of gallstones in Xenical patients were reported to the Food and Drug Administration between April 1999 and December 2006, the agency staff found.

The memo was released ahead of presentations to an FDA advisory panel meeting on Wednesday about the use of Xenical and several other drugs in children.

There were no specific concerns about children using the drug, they staff said.

The agency reviewers said they will continue to examine the risk and will recommend label changes if warranted. Their probe will also look at post-marketing data for other drugs that treat obesity.

Xenical, also known by its chemical name, orlistat, is approved in the United States and aims to prevent fat from being absorbed by the body. It is also available in an over- the-counter version called alli, licensed by GlaxoSmithKline Plc (GSK.N)(GSK.L).

Gallstones, which often do not trigger any symptoms, are formed by an excess of water, salt, cholesterol and other substances excreted from the liver and can cause painful blockages.

While weight-loss products are important, "there is a need to understand the overlay of the drug adverse effect over and above the natural history of gallstone disease in the obese population" who can have other complications, the reviewers wrote March 1.

The memo was posted on the FDA's Web site here Representatives for Roche could not be immediately reached for comment.

((Reporting by Susan Heavey; editing by Andre Grenon; Reuters Messaging: susan.heavey.reuters.com@reuters.net +1-202-354- 5848)) Keywords: ROCHE XENICAL/

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