IS ACETAMINOPHEN EFFECTIVE IN EASING BACK PAIN AND KNEE PAIN?
Machado GC, Maher CG, Ferreira PH, et al. Efficacy and safety of paracetamol for spinal pain and osteoarthritis: systematic review and meta-analysis of randomised placebo controlled trials. BMJ. 2015;350:h1225. doi: 10.1136/bmj.h1225.
Acetaminophen is ineffective in treating lower back pain and provides minimal short-term benefit for people with osteoarthritis, a systematic review of 13 randomized, placebo-controlled trials reports.
Two independent reviewers extracted data on pain, disability, and quality of life, as well as adverse effects, patient adherence, and use of rescue medication, and found high-quality evidence that:
• Acetaminophen is ineffective for reducing pain intensity and disability, or improving quality of life in patients with low back pain.
• Acetaminophen provides significant, but not clinically important, benefit for pain and disability in patients with hip or knee osteoarthritis.
• Patients taking acetaminophen are nearly four times more likely to have abnormal results on liver function tests.
COMMENTARY
This study adds to the literature a less potent effect of acetaminophen than we have previously assumed,1,2 suggesting a significant but not clinically important effect on pain. This result is at odds with the experience of many clinicians, who use acetaminophen regularly as a first-line agent for pain. When there is a dissonance between clinical experience and emerging evidence, one has to ask why. The explanation here may be that acetaminophen, NSAIDs, and opioid analgesics all have their problems and all seem to work better for some patients than others. In clinical practice, we often start with acetaminophen, which works for some patients, and go on to other agents for those in whom acetaminophen does not provide sufficient pain control. Studies that report a small mean effect may not detect the significant effect that can occur for many patients but gets hidden in the mean (which includes patients in whom there is no effect). I am reminded of the statistician who drowned in a river with a mean depth of 3 feet. A common clinical approach, often starting with well-tolerated acetaminophen and then progressing to other agents when needed, still seems sound. —NS
REFERENCES
1. Bannuru RR, Schmid CH, Kent DM, et al. Comparative effectiveness of pharmacologic interventions for knee osteoarthritis: a systematic review and network meta-analysis. Ann Intern Med. 2015;162(1):46-54. doi: 10.7326/M14-1231.
2. Williams CM, Maher CG, Latimer J, et al. Efficacy of paracetamol for acute low-back pain: a double-blind, randomised controlled trial. Lancet. 2014;384(9954):1586-1596. doi: 10.1016/S0140-6736(14)60805-9.
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