The American Food and Drink Administration has announced plans to monitor more carefully usage of the anti-obesity medication Alli, the lower-strenth version of the prescription-only medication Xenical.

The body has received reports that orlistat may have been causing rare cases of hepatitis and other abnormalities related to the liver. The FDA have said that while they have not decided whether stricter regulation of Alli usage is needed, they will be watching out for any further reports.

When Alli was introduced, some critics said that they were worried that there would not be the same doctor’s monitoring as would be received by a patient taking Xenical. In an edition of the medical journal The Lancet, experts expressed fears that over-the-counter purchase of orlistat might lead people to perceive obesity as something that could be cured just by popping pills.

Since Alli was launched in April, regulators at the MHRA have received reports that 31 people experienced adverse side-effects from taking the pills, Some reports have suggested that pharmacists are not checking carefully enough that patients buying the slimming pills are sufficiently overweight to merit medical intervention.

It is believed that regulators will follow the lead of the FDA should they decide to introduce more stringent regulations. Roche, the manufacturers of orlistat, have denied there is a link between the drug and liver toxicity.