The U.S. government this week warned against the online marketing of unlicensed health remedies claiming to protect against H1N1 swine flu infection, including fake "Tamiflu" pills from India.

The Food and Drug Administration reported Thursday that it had purchased and analyzed several products represented on the Internet as Tamiflu, Roche Holding AG's brand name version of the antiviral drug oseltamivir.

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One order, which arrived in an unmarked envelope from India, consisted of unlabeled white pills that contained talc and the common pain reliever acetaminophen, the FDA said. Others contained various amounts of oseltamivir but were not approved for use in the United States.

In one action, the FDA and the Federal Trade Commission ordered well-known author and doctor Andrew Weil to stop marketing his Immune Support Formula to protect against the H1N1 flu virus.

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"Claims that a dietary supplement can prevent, treat or cure human infection with the H1N1 virus must be supported by well-controlled human clinical studies," the regulatory agencies said in a warning letter to Weil.

Officials at Weil's Phoenix, Arizona-based headquarters were not immediately available for comment.

"Products that are offered for sale online with claims to diagnose, prevent, mitigate, treat or cure the 2009 H1N1 influenza virus must be carefully evaluated," FDA Commissioner Dr. Margaret Hamburg said in a statement.

Swine flu, which emerged in March, spread quickly around the world, and was declared a pandemic in June, poses a serious health threat because most people lack immunity to it.

But U.S. health officials say the most effective protection against infection is vaccination and the federal government hopes to offer as many as 250 million vaccine doses to the public by the end of the year.

The government has ordered vaccine from five companies — Sanofi-Aventis SA, CSL Ltd, Novartis AG, GlaxoSmithKline and the AstraZeneca unit MedImmune.

Once someone is already infected, oseltamivir and another antiviral drug called zanamivir — an inhaled medicine produced as Relenza by GlaxoSmithKline Plc can help relieve the severity of disease.

Widespread and unnecessary use threatens to make the H1N1 virus resistant to the antivirals, which would render them ineffective as medicine for people with severe flu cases.

Health officials have already reported H1N1 resistance to Tamiflu.