A slimming drug available over the counter in the UK is being investigated for links to 32 cases of liver damage by the US Food and Drug Administration.

The FDA began investigating orlistat, sold over the counter as Alli, and its potential links to liver damage earlier this year after concerns were raised about potentially harmful side effects. On Monday, the agency said it was assessing 32 reports of serious liver injury in patients, 27 of whom were hospitalised.

Alli works by absorbing about a quarter of the fat from food and preventing it from being retained as extra weight. It went on sale in the UK in April and is available to dieters without a prescription. About 200,000 people in the UK have purchased the drug. Tablets are available to adults deemed to be overweight – with a body mass index (BMI) of 28 or over – following a consultation with a pharmacist.

Alli became the first weight-loss drug approved by the FDA to be sold over the counter in the US in 2007. The FDA said the most commonly reported adverse reactions included the yellowing of skin or whites of the eyes, weakness and stomach pain. Of the 32 reports of liver damage received between 1999 and 2008, 30 occurred outside the US. Britain's Medicines and Healthcare Products Regulatory Agency said it had received a total of 1,295 suspected adverse drug reaction reports associated with orlistat since it was licensed in 1998.

The manufacturer, GlaxoSmithKline, said there was "no evidence" that Alli caused liver damage and that the active ingredient orlistat was "the most-studied weight loss medicine". It added: "Any routine assessment from a regulatory body does not mean that a risk or causal relationship exists."