Orlistat is a commonly prescribed anti-obesity drug, but there have been concerns that it might damage the liver. This study, using GP and hospital data, showed that although liver injury is more likely when Orlistat is prescribed, this is probably the result of someone’s declining health triggering the decision to take the drug, rather than the drug itself.

Why was this work needed?

Orlistat is widely used worldwide and is available on the NHS to promote weight loss when advised by a doctor. It works by preventing some of the fat in the food you eat from being absorbed. However, in the past, there have been concerns that it may cause liver damage. This would be particularly concerning, given its widespread use and the lack of alternatives.

What happened?

Although clinical trials had already suggested that orlistat did not cause liver injury, these trials were too small to study a potentially rare outcome like liver injury. To do this, a much larger number of patients using orlistat in the real world was needed.

Therefore, this research linked GP and hospital data to assess whether the use of orlistat was connected to an increased rate of acute liver injury.

What were the benefits?

The research found that although the chance of having liver injury was increased immediately after someone started taking orlistat, the risk was also increased in the period immediately before the prescription. The researchers concluded that the cause of the liver injury was probably not orlistat, but the declining health of the person that led to the decision to begin the treatment. This reassures doctors and patients of the safety of using orlistat for weight loss.

What type of data was involved?

This study used data from the Clinical Practice Research Datalink (CPRD) and Hospital Episode Statistics (HES) data.

The linkage between CPRD and HES data was carried out independently by NHS Digital. Data was de-personalised before being accessed by the researchers.

Who funded and collaborated on this work?

This study was conducted by researchers at the London School of Hygiene and Tropical Medicine.

Where can I go for more information?


Orlistat and the risk of acute liver injury: self controlled case series study in UK Clinical Practice Research Datalink

NHS: Obesity treatment