The Food and Drug Administration on Monday has issued a warning to consumers involving a counterfeit version of GlaxoSmithKline's weight-loss 60 milligram capsules drug Alli, which is sold over the internet.

However, the drug is available with many retail stores also, but the matter came into being when the counterfeit version was purchased by consumers over the Internet, and GlaxoSmithKline was flodded with complaints about the product last month.

Glaxo claims the product was bought from online auction sites like eBay.

Tests conducted on a counterfeit product showed it didn't contain the active ingredient in Alli and instead contained sibutramine, which is the active ingredient in the prescription weight-loss drug Meridia, sold by Abbott Laboratories, which can be malignant if it interacts with some other medications.

Though the fake product is similar to Alli, however, there are some factors that enable users to spot a difference.

The fake capsule is larger in size, with white powder in contrast to the authentic drug Alli containing small sized white pellets. Also, its packaging does not bear a "lot" number. Last but not the least, there are no printed words on the inner foil safety seal.