The risk appears tiny. Worldwide, there have been only 13 cases among the 40 million people who have used the products. However, two of these people died and three others required liver transplants.
Alli and Xenical contain the weight loss drug orlistat. Xenical, made by Roche's Genentech, contains 120 milligrams of orlistat and is available only by prescription. Alli, from GlaxoSmithKline, contains 60 milligrams of orlistat and is available over the counter.
In 2009, the FDA announced it was reviewing 32 reports of liver injury in people taking Alli or Xenical. That review has now identified 13 cases, one in the U.S., of liver death or liver failure.
The fact that these patients were using the products does not necessarily mean the products caused the liver injury. Some of the patients were taking other drugs or had other conditions that may have contributed to the injury.
Nevertheless, the labels for Alli and Xenical will now carry warnings about the possible risk of liver injury.
Symptoms of liver injury include:
People concerned about the possibility of liver injury should consult a doctor.
In a news release, GlaxoSmithKline (GSK) said it was cooperating with the FDA in conjunction with Roche.
"GSK is committed to ensuring that consumers and physicians understand the safety profile of orlistat and Alli. Although reports of serious liver injury in people taking orlistat are rare, GSK takes all adverse events reports seriously," Howard Marsh, MD, chief medical officer for GSK Consumer Healthcare, says in a news release.