The Food and Drug Administration has warned shoppers to be on the lookout for counterfeit versions of the weight-loss drug Alli. The real version of Alli contains orlistat, a drug with side effects that include “an urgent need to defecate,” as those with delicate sensibilities like to put it. The fakes are made with sibutramine, a controlled substance that has been linked to high blood pressure in some studies.

According to the FDA, the counterfeit version of the GlaxoSmithKline drug “looks similar to the authentic product, with a few notable differences.”

The counterfeit Alli has:

• Outer cardboard packaging missing a “Lot” code;
• Expiration date that includes the month, day, and year (e.g., 06162010); authentic Alli expiration date includes only the month and year (e.g.,: 05/12);
• Packaging in a plastic bottle that has a slightly taller and wider cap with coarser ribbing than the genuine product;
• Plain foil inner safety seal under the plastic cap without any printed words; the authentic product seal is printed with “SEALED for YOUR PROTECTION”;
• Contains larger capsules with a white powder, instead of small white pellets.

The FDA also warns that “sibutramine is a drug that should not be used in certain patient populations or without physician oversight. Sibutramine can also interact in a harmful way with other medications the consumer may be taking.”

If you think you have fake Alli, you can contact the FDA’s Office of Criminal Investigations by calling 800-551-3989 or by visiting the OCI Web site. If you have the real stuff, you don’t have to contact the FDA, but you may want to stock up on Depends.

FDA Warns Consumers about Counterfeit Alli [FDA Press Release]

Previously: Glaxo Funding Fat Film To Promote Poop-Causing Drug

Want more consumer news? Visit our parent organization, Consumer Reports, for the latest on scams, recalls, and other consumer issues.