US authorities are investigating concerns an anti-obesity drug widely available over the counter at chemists may cause liver damage.
Orlistat went on sale under the brand name Alli without the need for a prescription in the UK in April.
The US Food and Drug Administration has received more than 30 reports linking the drug to serious liver injury.
However, manufacturer GlaxoSmithKline said there was no evidence the drug caused liver damage.
In six of the cases reported to the FDA patients went on to develop organ failure.
The pill, which works by blocking the absorption of fat in the body, is aimed at adults with a Body Mass Index (BMI) of 28 or more. It is also available on prescription as Xenical.
Clinical trials suggest adding orlistat to a reduced-calorie, lower-fat diet, can help people lose 50% more weight than dieting alone.
