December 22 (HealthDay News) -- The U.S. Food and Drug Administration warned consumers Monday to avoid more than two dozen products marketed for weight loss because they contain undeclared ingredients that could pose serious health risks.

The products are sold in some retail stores and on the Internet and some claim to contain only "natural" or "herbal" ingredients. But the undeclared ingredients (not listed on labels) range from an anti-seizure medication to a suspected carcinogen, the FDA said.

The FDA identified the weight loss products as: Fatloss Slimming, Japan Lingzhi 24 Hours Diet, 7 Day Herbal Slim, 999 Fitness Essence, Imelda Perfect Slim, Perfect Slim, ProSlim Plus, Slim Express 360, Superslim, Venom Hyperdrive 3.0, 2 Day Diet, 5x Imelda Perfect Slimming, 8 Factor Diet, Extrim Plus, Lida DaiDaihua, Perfect Slim 5x, Royal Slimming Formula, Slimtech, TripleSlim, 3x Slimming Power, 3 Day Diet, 7 Diet Day/Night Formula, GMP, Miaozi Slim Capsules, Phyto Shape, Slim 3 in 1, Somotrim, and Zhen de Shou.

"These tainted weight loss products pose a great risk to public health because they contain undeclared ingredients and, in some cases, contain prescription drugs in amounts that greatly exceed their maximum recommended dosages," Dr. Janet Woodcock, director of the FDA's Center for Drug Evaluation and Research, said in a news release. "Consumers have no way of knowing that these products contain powerful drugs that could cause serious health consequences. Therefore, FDA is taking this action to protect the health of the American public."

The FDA said an analysis found that the undeclared ingredients in some of these products include sibutramine (a controlled substance), rimonabant (a drug not approved for marketing in the United States), phenytoin (an anti-seizure medication), and phenolphthalein (a solution used in chemical experiments and a suspected cancer-causing agent). Some of the amounts of active ingredients greatly exceed FDA-recommended levels, putting consumers' health at risk, the agency said.

The risks posed by these products can be serious, the FDA said. For instance, sibutramine, which was found in many of the products, can cause high blood pressure, seizures, palpitations, heart attack or stroke. The drug can also interact with other medications that patients may be taking and increase their risk of serious side effects. The safety of sibutramine also hasn't been determined for women who are pregnant or breast-feeding, or in children younger than 16 years of age, the agency said.

Rimonabant was evaluated -- but not approved -- by the FDA for marketing in the United States. The drug, which has been approved in Europe, has been associated with increased risk of depression and suicidal thoughts and has been linked to five deaths and 720 adverse reactions in Europe during the last two years, the agency said in the news release.

Consumers who have used any of these products should stop taking them immediately and consult their health-care professional. And consumers should always seek the guidance of a health-care professional before purchasing weight loss products, the FDA said.

The FDA said it has inspected a number of companies linked to the sale of these products, and is currently seeking to have the products recalled. Citing its own inspections and what it called the companies' "inadequate responses to recall requests," the agency said it may take additional action, including issuing warning letters or seeking criminal charges.

Health care professionals and consumers should report serious side effects or product quality problems to the FDA's MedWatch Adverse Event Reporting program. The e-mail address is www.fda.gov/MedWatch/report.htm. Or call (800) FDA-1088 or Fax (800) FDA-0178.

SOURCE: U.S. Food and Drug Administration, news release, Dec. 22, 2008