Any link between orlistat and acute liver injury is explained by changes in patients’ underlying health status and is non-causal, suggest UK researchers.
The researchers analysed UK Clinical Practice Research Datalink information and corresponding Hospital Episode Statistics Data for 94,695 patients with a least one prescription of orlistat, for the period 1999 to 2011. They identified 988 patients with definite or probable idiopathic liver injury during this period and compared the age-adjusted risk of liver injury during periods of orlistat use with periods of non-use.
Researchers found the incidence of acute liver injury was increased in a short period both before and after the start of treatment, suggesting treatment initiation tends to coincide with a time of increased risk of liver injury. The risk of liver injury was 2.2 times higher in the first 30 days of treatment than in periods of non-use, but was not elevated for treatment periods beyond 30 days. However, the risk of liver injury was also increased 1.5 fold in the 90 days preceding initiation of orlistat; further analysis revealed that the risk was no higher in the 90 days after treatment started than it was in the 90 days beforehand.
What this means for GPs
The results suggest the relationship between orlistat use and liver injury is non-causal. The researchers conclude: ‘Our results imply that studies based only on traditional epidemiological designs or spontaneous adverse events are likely to detect associations between starting orlistat treatment and liver injury, but such associations should not be interpreted as evidence for an adverse causal effect of the drug unless an increased risk in the period immediately before the start of treatment can be excluded.’