Paracetamol has no clinical effect in treating osteoarthritis pain or improving physical function, according to a large-scale analysis of pain-relief medication.
The study, published today in The Lancet, found that while paracetamol was slightly better than a placebo, it did not meet the minimum standard of clinical effectiveness for patients with knee and hip osteoarthritis. Taken on its own, the researchers say paracetamol has no role in the treatment of patients with osteoarthritis, regardless of the dose administered.
The researchers put together the largest analysis of randomised trials of medical pain relief for osteoarthritis to date, pooling data from 74 randomised trial published between 1980 and 2015. They found the non-steroidal anti-inflammatory drug (NSAID) diclofenac was the most effective short-term pain relief. However, they cautioned against the long-term used of NSAIDs because of known side-effects, such as stomach ulcers or kidney problems.
Globally, about 10% of men and 18% of women over the age of 60 have osteoarthritis, with estimates that 26.9 million adults in the USA and 8.75 million in the UK are afflicted. It is the leading cause of pain in elderly people and by impairing physical activity can increase the risk of obesity, cardiovascular disease and diabetes.
The researchers said that paracetamol and NSAIDs are often the first line treatment for mild to moderate pain management for those affected by osteoarthritis, but paracetamol is more commonly used because of the cardiovascular and gastrointestinal side effects associated with long-term NSAID use.
All of the 22 preparations of medications included in the analysis, irrespective of dose, improved pain symptoms above a placebo. But the small effect granted by paracetamol was only slightly better than placebo and did not reach the minimum clinically important difference.
In contrast, diclofenac at the maximum dose (150mg/day) was the most effective and beat out maximum doses of other frequently used NSAIDs, including ibuprofen, naproxen and celecoxib.University of Bern’s Dr Sven Trelle said paracetamol was often prescribed to manage long-term pain caused by osteoarthritis because of the side effects of NSAIDs. “However, our results suggest that paracetamol at any dose is not effective in managing pain in osteoarthritis, but that certain NSAIDs are effective and can be used intermittently without paracetamol.”
University of Bern’s Dr Sven Trelle said paracetamol was often prescribed to manage long-term pain caused by osteoarthritis because of the side effects of NSAIDs. “However, our results suggest that paracetamol at any dose is not effective in managing pain in osteoarthritis, but that certain NSAIDs are effective and can be used intermittently without paracetamol.”
“NSAIDs are some of the most widely used drugs for patients with osteoarthritis. There is a range of different drugs at different dosages that doctors can prescribe, but patients often switch between drugs, or stop taking them because the first one they use hasn’t sufficiently helped control the pain. We hope our study can help better inform doctors about how best to manage pain in this population.”
Most of the trials included in the analysis had follow-ups of three months or less, which the authors said other studies with longer-term follow-up might be necessary.
In a related commentary, Professor Nicholas Moore and colleages from the University of Bordeaux said the study was limited because other widely-used NSAIDs were not included, probably because there were no suitable trials to assess. “These omissions are unfortunate because these drugs might be as effective but much cheaper than the newest drugs.”
“The most remarkable result is that paracetamol does not seem to confer any demonstrable effect or benefit in osteoarthritis, at any dose. This finding is not entirely unexpected. Paracetamol has been on the market for as long as most of us remember. Its efficacy has never been properly established or quantified in chronic diseases, and is probably not as great as many would believe. Its safety is also questioned, not just in overdose.”
“Many patients could be suffering needlessly because of perceived NSAIDs risks and paracetamol benefits (which might not be real). Perhaps researchers need to reassess both these perceptions (or misconceptions) and the use of other analgesic options that have been discarded over time, such as dipyrone.”