The U.S. Food and Drug Administration (FDA) is issuing a warning for consumers and health care professionals who use or recommend the use of the weight loss medication orlistat, marketed as Xenical and Alli. The use of these medications could lead to a rare occurrence of severe liver injury in patients.

The FDA’s will update safety information and labeling based on a review of cases of severe liver injury reported in individuals taking orlistat. The agency has identified 13 cases of severe liver injury, 12 of which were reports from outside of the United States. The only U.S. report of severe liver injury involved Alli. At this time, a cause-and-effect relationship of severe liver injury with orlistat use has not been established.

People who take Xenical or Alli should be aware that liver injury with orlistat – while rare – has been reported. Those taking the drug also should be aware of the signs and symptoms of liver injury, which include itching, yellow eyes or skin, dark urine, loss of appetite, or light-colored stools.