The US Food and Drug Administration (FDA) warned Saturday, lab tests had shown counterfeit versions of GlaxoSmithKline’s over-the-counter diet pill Alli, contained dangerously high levels of sibutramine, a prescription weight loss ingredient, also an active ingredient in Abbott Laboratories Inc.’s prescription diet drug Meridia.

Dr. Janet Woodcock, Head of FDA’s drug unit in a conference call told reporters, excessive amounts of sibutramine in fake Alli pills posed a serious health risk, as any individual taking the fake pills faced exposure to twice the maximum prescription dose of sibutramine every day.

Earlier this week, people with a history of cardiovascular disease had received an FDA warning about taking sibutramine saying it raised a risk of heart attack and stroke.

While, FDA has only issued a warning about sibutramine, Abbott Laboratories has suspended sales of the drug in Europe after European regulators concluded it was far too risky.

According to Woodcock, the counterfeit diet pills could cause adverse effects even healthy people, such as, sleepiness, palpitations, anxiety, nausea and slight elevation in blood pressure.

FDA officials believe there is no evidence of counterfeit versions of Alli in stores, but it can be bought over the Internet, as well as, from online auction sites. The counterfeit versions are being sold as 60-milligram capsules in 120-count refill kit only.

All Alli consumers have been urged to check products for genuineness, discarding immediately if fake. The outer packaging of counterfeit versions has a missing lot code, the expiration date includes the month, day, and year, compared to Glaxo’s Alli that includes only the month and the year i. e. 5/12.

As well, authentic Alli’s foil seal reads SEALED FOR YOUR PROTECTION in white ink, while the fake Alli’s is plain with not printing, including counterfeit versions of the Alli capsules being larger than the genuine product which is pellet shaped and its contents are powdery.

Glaxo is working with the FDA for removing the counterfeits removed from online auction sites, including alerting consumers about the differences between the counterfeit and legitimate products.

FDA and Glaxo hasve asked consumers to purchase Alli only from reputable retailers or from their branded online Web sites. They have also been asked to get in touch with FDA’s Office of Criminal Investigations by calling 800-551-3989 or use the agency’s web site http://www.fda.gov/OCI.