Efficacy and safety of paracetamol for spinal pain and osteoarthritis: systematic review and meta-analysis of randomised placebo controlled trials
BMJ 2015; 350 doi: http://dx.doi.org/10.1136/bmj.h1225 (Published 31 March 2015)

Objective
To investigate the efficacy and safety of paracetamol (acetaminophen) in the management of spinal pain and osteoarthritis of the hip or knee.

Design Systematic review and meta-analysis.

Data extraction
Two independent reviewers extracted data on pain, disability, and quality of life. Secondary outcomes were adverse effects, patient adherence, and use of rescue medication. Pain and disability scores were converted to a scale of 0 (no pain or disability) to 100 (worst possible pain or disability). We calculated weighted mean differences or risk ratios and 95% confidence intervals using a random effects .

Results
12 reports (13 randomised trials) were included. There was “high quality” evidence that paracetamol is ineffective for reducing pain intensity (weighted mean difference ?0.5, 95% confidence interval ?2.9 to 1.9) and disability (0.4, ?1.7 to 2.5) or improving quality of life (0.4, ?0.9 to 1.7) in the short term in people with low back pain.
For hip or knee osteoarthritis there was “high quality” evidence that paracetamol provides a significant, although not clinically important, effect on pain (?3.7, ?5.5 to ?1.9) and disability (?2.9, ?4.9 to ?0.9) in the short term.
The number of patients reporting any adverse event (risk ratio 1.0, 95% confidence interval 0.9 to 1.1), any serious adverse event (1.2, 0.7 to 2.1), or withdrawn from the study because of adverse events (1.2, 0.9 to 1.5) was similar in the paracetamol and placebo groups. Patient adherence to treatment (1.0, 0.9 to 1.1) and use of rescue medication (0.7, 0.4 to 1.3) was also similar between groups. “High quality” evidence showed that patients taking paracetamol are nearly four times more likely to have abnormal results on liver function tests (3.8, 1.9 to 7.4), but the clinical importance of this effect is uncertain.

Conclusions
Paracetamol is ineffective in the treatment of low back pain and provides minimal short term benefit for people with osteoarthritis.
These results support the reconsideration of recommendations to use paracetamol for patients with low back pain and osteoarthritis of the hip or knee in clinical practice guidelines.

What is already known on this topic

Clinical guidelines recommend paracetamol as first line analgesic drug for both spinal pain (neck and low back pain) and osteoarthritis of the hip and knee
The evidence base supporting these recommendations has recently been called into question

What this study adds

High quality evidence suggests that paracetamol is ineffective in reducing pain and disability or improving quality of life in patients with low back pain
There is high quality evidence that paracetamol offers a small but not clinically important benefit for pain and disability reduction in patients with hip or knee osteoarthritis
Though high quality evidence shows that patients taking paracetamol are nearly four times more likely to have abnormal results on liver function tests compared with those taking oral placebo, the clinical relevance of this is unclear.

G Mohan.