Investigations have begun into the only non-prescription weight-loss drug approved by the Food and Drug Administration (FDA) after reports it causes liver damage.
Regulators say they have received more than 30 reports of liver damage in patients taking the drugs alli and Xenical, which is the prescription version of the drug.
Reports submitted between 1999 and October 2008 include cases of 27 patients who were hospitalised and six who suffered liver failure.
Alli and Xenical are marketed by British drugmaker GlaxoSmithKline, but Xenical is manufactured by Swiss firm Roche.
So far, a relationship has not been identified between the drugs and liver damage and the FDA has advised patients to continue taking the drugs as directed.
However, it added: “Consumers should consult their health care professional if they are experiencing symptoms of liver damage including fatigue, fever, nausea and vomiting.”
A spokeswoman for GlaxoSmithKline said there is no evidence which links the drug and alli has been safety-tested on more than 30,000 patients enrolled in 100 clinical studies.
She added: “Liver changes can have many causes. People who are overweight and obese are predisposed to liver-related disorders.”