But the agency does recommend that patients tell their doctor if they are having symptoms such as weakness, fatigue, fever, jaundice or brown urine. Abdominal pain, nausea, vomiting, light-colored stools, itching and loss of appetite might also signal trouble.
Monday's move follows reports of 32 cases of serious liver injury, including six cases of liver failure, between 1999 and October of 2008.
More commonly, patients reported having jaundice, weakness and abdominal pain. For 27 patients, the symptoms were severe enough to require hospitalization.
Two of the cases occurred in the United States, the rest originated overseas.
In 10 years of being on the market, this isn't a great number, Pfanner noted.
The Drug Safety Oversight Board, part of FDA's Center for Drug Evaluation and Research, first looked into the issue in April. The agency stressed that there is no established association or evidence of a cause-and-effect relationship at this time.
The FDA first approved orlistat as a prescription medicine in 1999. In 2007, it became the first nonprescription drug approved to treat obesity in American adults.
The prescription version of the drug comes in 120-milligram capsules while the over-the-counter version is available in 60-milligram pills. Both versions are designed only to be used in conjunction with a reduced-calorie, low-fat diet by overweight adults aged 18 and older.
In 2006, the consumer advocacy group Public Citizen petitioned the FDA to remove Xenical from the U.S. market, not because of liver-related issues but because it might increase the risk of aberrant crypt foci, believed to be precursors to colon cancer.
The FDA's approval of the first over-the-counter drug for weight loss came as the United States and other western nations are struggling with an unprecedented obesity epidemic.
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