What is the background to this study?

Tapentadol is an opioid medicine which is prescribed for pain and is believed to have different side effects than other opioid medicines such as morphine. While a number of side effects have been reported by patients taking tapentadol, there was previously no existing description of how likely or certain these were to occur.

What did we want to find out?

We wanted to look at the side effects of tapentadol, particularly those affecting a patient’s digestive system, in patients with chronic pain. We also wanted to find out how these differed when compared with other opioid drugs. Our intention was to better inform clinicians prescribing the drug about the likelihood of potential side effects. We also wanted to show that the research methods used can be a very useful tool in helping researchers identify how much is known about a drug’s effects, and how much is still uncertain.

What did we do?

We looked at constipation and other side effects of tapentadol using a statistical technique called ‘confidence evaluation in network meta-analysis’. A meta-analysis is a study designed to systematically assess the results of previous studies (usually randomised control trials) in order to come to conclusions about existing evidence as a whole. A confidence evaluation of those results additionally allows us to state how confident we are in the results of the existing body of research, considering factors such as bias, how precise the results are, and how coherent the results are as a whole. In this instance we compared the reported side effects of tapentadol with other opioid medications and used the confidence evaluation to assess confidence in those comparisons.

What did we find?

We looked at 25 studies in total. Regarding the overall risk of side effects we found that there was a major concern over the precision of the comparison of tapentadol versus other opioid drugs. However, when considering the effects of tapentadol against one of these drugs, oxycodone, we were able to assert with a high level of confidence that the former was associated with a lower incidence of constipation than the latter.

Why is this important?

The confidence evaluation in network meta-analysis allowed us not only to compare the results of the studies, but also to assess how confident we could be in these comparisons. When compared broadly to other opioid medications the relative effects of tapentadol showed possible imprecision, heterogeneity and / or incoherence, suggesting more research is needed in this area. However, we were able to see that tapentadol was associated with a lower incidence of constipation than one of these drugs in particular, oxycodone. More broadly this shows the usefulness of using confidence analyses when comparing the results of multiple studies.

Who authored this study?

This study was authored by Professor Patrice Forget, who is a Professor of Anaesthesia at the Epidemiology Group, and Mathieu Vermeersch who is a trainee in Anaesthesia.

Who funded this work?

This work was performed at the Vrije Universiteit Brussel and in the Epidemiology Group, Institute of Applied Health Sciences, University of Aberdeen. It was funded directly by the institutions themselves, and not externally funded.

Where can I find out more?

You can read the full article here.