The US Food and Drug Administration (FDA) announced this week that it is reviewing reports of liver injury in people who took the weight loss drug orlistat, which is marketed as the prescription drug Xenical and over the counter (OTC) as Alli. However, the federal agency said in the meantime consumers should continue to use the product as prescribed or directed.

The FDA said that it had received 32 adverse event reports between 1999 and 2008 of serious liver injury in people taking orlistat, 30 of which had occurred outside the US. Of the 32 cases, 27 reported hospitalization and 6 developed organ failure.

The most commonly reported signs of liver injury in the reports included jaundice (where the skin and the whites of the eyes go yellow), weakness and stomach pain.

All the reports received by the FDA, plus suspected cases of liver injury included in data submitted by the manufacturers of the drug, are being reviewed by the FDA’s Center for Drug Evaluation and Research Drug Safety Oversight Board, whose executive director, Dr Steven Osborne told the media:

“The issues here are complex, but FDA has benefited from the input of the Board, including comments from representatives from three FDA Centers and several other Agencies in the Department of Health and Human Services.”

The FDA stressed that it is still analysing the data and as yet no definite link has been established between liver injury and orlistat. The agency said it will release the findings as soon as they are done.

According to the BBC, GlaxoSmithKline, the company that makes Alli, the over the counter version of orlistat, maintains there is no evidence the drug causes liver damage. The prescription version, Xenical is made and marketed by Roche, whose representatives, according to the Wall Street Journal, were not immediately available for comment.

The FDA does not advise doctors to change their prescribing habits and stressed that the announcement is intended to keep the public informed of the agency’s concerns and actions. In the meantime:

“Consumers taking Xenical should continue to take it as prescribed, and those using over-the-counter Alli should continue to use the product as directed,” said the FDA.

However, consumers who have used the drug should see their doctor if they experience any symptoms of developing liver injury, particularly “weakness or fatigue, fever, jaundice, or brown urine”.

Other symptoms may include “abdominal pain, nausea, vomiting, light-colored stools, itching, or loss of appetite”, said the FDA, who also urged consumers and health care professionals to report any suspected side effects from using orlistat via the agency’s MedWatch Adverse Event Reporting system.

Orlistat works by blocking the enzymes that break down fats in the digestive system thereby reducing the amount of fat absorbed by the body. The drug, which is designed to treat obesity, should only be used in conjunction with a low fat, reduced calorie diet.

Trials suggest that used in this way, the drug can help people lose about 50 per cent more weight than dieting alone.

As with any medication, always read the label and accompanying information and make sure you understand about the possible side effects and whether you are in a group that should not take the drug.

— FDA

Sources: FDA, BBC, Wall Street Journal.

Written by: Catharine Paddock, PhD