UPDATE 3-US warns Bayer over aspirins containing supplements

(Recasts, adds company and congressional comment, updates shares to close)

By Susan Heavey

WASHINGTON, Oct 28 (Reuters) - Two over-the-counter Bayer AG BAYG.DE aspirin products that contain dietary supplements have not been proven to work and are being sold illegally, U.S. health regulators warned on Tuesday.

Claims made about the products, Bayer Aspirin with Heart Advantage and Bayer Women's Low Dose Aspirin + Calcium, also mislead consumers, the U.S. Food and Drug Administration said.

"These are not FDA-approved products," agency spokeswoman Rita Chappelle said. "They are selling products that are illegal."

The FDA stopped short of calling for the pain relievers to be removed from store shelves but urged the company to take "prompt action" or else face legal action.

But Bayer defended the medications and its right to market them.

"We stand behind both products and all marketing claims made in their support," the German drugmaker said in a statement.

The company added that its advertisements tell buyers to check with their doctors before taking the combination aspirins. Bayer Aspirin with Heart Advantage also tells consumers the drug does not replace cholesterol-lowering medication.

Bayer Aspirin with Heart Advantage contains plant sterols and claims on its packaging to help control cholesterol, while Bayer Women's Low Dose Aspirin + Calcium claims to help strengthen bones and prevent osteoporosis.

"These statements on the labeling send consumers a mixed message about the purpose of the product and the duration for which it can be safely used," the FDA wrote in an Oct. 27 warning letter to the company released on Tuesday.

FDA officials gave Bayer 15 days to respond to the warning. To comply, the drugmaker could stop selling the products or conduct clinical trials and seek FDA approval.

If the company does not take proper action, the FDA could seize the product, seek an injunction or take other legal steps. Bayer said it was reviewing the agency's letter.

The drugmaker's marketing of its Heart Advantage aspirin is also the subject of a congressional investigation.

Earlier this month, the U.S. House of Representatives Energy and Commerce Committee began probing whether Bayer misled the public by marketing the combination product directly to consumers.

"Our investigation will continue," committee Chairman John Dingell, a Michigan Democrat, said.