Paracetamol is not more effective than placebo against osteoarthritis pain

Osteoarthritis is the most common joint disease worldwide. In Switzerland, 20 percent of the population over the age of 60 is affected. The disease leads to pain, function restrictions of the joints, reduced physical activity and also to an increased mortality risk.

The treatment of pain follows a step-wise approach in which the drug paracetamol as well as the class of so-called non-steroidal anti-inflammatory drugs (NSAIDs) play a central role. A large number or preparations from the latter are on the market. Up to now, recommendations and guidelines do not differentiate between NSAIDs and paracetamol or between the individual preparations from the group of NSAIDs. In this respect, it was not known whether the various preparations differ in terms of their pain-relieving efficacy. Now a group of researchers led by Sven Trelle from the clinical trials unit of the Faculty of Medicine of the University of Bern and Bern University Hospital (CTU Bern) as well as from the Institute of Social and Preventive Medicine at the University of Bern examined this for the first time. In a comprehensive meta-analysis the researchers were able to prove that paracetamol is not clinically more effective than placebo against pain and that the medicine diclofenac – and, with a few concessions – etoricoxib are most effective with regard to pain and function. The study has now been published in the journal “The Lancet”.

Guidance for the use of medications

Results of 74 trials with 58,556 patients were taken into consideration for the analysis. The effect of a total of 22 medical treatments and placebo were examined in terms of pain reduction and improvement of function. These 22 therapies included different doses of paracetamol and of seven different NSAIDs. The individual effectiveness of these different treatments has been shown for the first time. “Physicians must decide together with affected patients which treatment they use”, says the last author of the study, Sven Trelle from CTU Bern. “Our study helps that this decision can now be made on a more solid basis.”

Innovative method

In the analysis at hand, the research group identified all randomised-controlled trials in which patients with knee or hip osteoarthritis received a placebo or one of the 22 differently dosed medications, and in which the effect on pain and function was measured. The results of all trials were then summarised with a special statistical method, a so-called “network meta-analysis”. “Normally, only comparisons of therapeutic methods are combined in a meta-analysis, if they were conducted directly within a trial. But network meta-analysis allows to combine these direct comparisons of therapies with indirect comparisons, which can be made across two trials in a type of network”, says Bruno da Costa from the Bern Institute of Primary Care (BIHAM), the first author of the study.

Short-term use recommended

As the research group has already shown in earlier works, the medications examined can have considerable adverse effects, especially if they are used as long-term therapy. For instance, diclofenac increases the risk of cardiovascular death. Because of their often advanced age and frequent multiple intake of medications, the choice of the right medication poses a particular challenge in patients with osteoarthritis–. This is why the researchers not only recommend a thorough consideration of the efficacy and all potential adverse effects, but also the shortest possible use of these medications. “Osteoarthritis pain is often episodic, and due to the side effects we recommend prescribing NSAIDs as short as possible”, says Stephan Reichenbach, a rheumatologist and also a co-author of the study.