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Acetaminophen Ineffective for Lower Back Pain

Findings challenge existing recommendations

Acetaminophen –– known as paracetamol in the United Kingdom –– is not effective in the treatment of spinal pain and provides negligible benefits for patients with osteoarthritis (OA), according to a study published April 1 in the British Medical Journal.

Spinal pain, which includes neck and lower-back pain, and OA, the most common form of arthritis, are leading causes of disability worldwide. Clinical guidelines recommend acetaminophen/paracetamol as the first-line drug treatment for both conditions, but the evidence to support this recommendation is weak and inconsistent, and there are safety concerns with the recommended full dosage (up to 4,000 mg/day). For these reasons, the recent move by the National Institute for Health and Care Excellence (NICE) in the U.K. to continue to recommend paracetamol for OA has been considered controversial.

Lead author Dr. Gustavo Machado, of the University of Sydney in Australia, and his colleagues conducted a systematic review to examine the efficacy and safety of paracetamol for lower-back pain and for OA of the hip or knee. The meta-analysis included 13 randomized controlled studies that looked at the effects of paracetamol compared with those of placebo: 10 trials included 3,541 patients who used paracetamol for OA of the hip or knee, and three trials included 1,825 patients who used paracetamol for lower-back pain.

The investigators evaluated the reduction of pain intensity; improvements in disability and quality of life; safety; and treatment adherence.

The study showed that for lower-back pain, paracetamol had no effect and did not reduce disability or improve quality of life compared with placebo. For OA, the investigators found small, clinically unimportant improvements in pain and disability compared with placebo.

The use of paracetamol in OA was also shown to increase the likelihood of abnormal results on liver function tests by almost four times compared with placebo, but the clinical relevance of this is still not certain, the authors said.

Adverse events (AEs) varied across the trials, but no differences were found in terms of the number of patients using paracetamol who reported AEs or who withdrew from studies because of AEs compared with those using placebo.

Moreover, treatment adherence rates were similar between those taking paracetamol and those using placebo.

The trials evaluated only short-term use of paracetamol, with the longest follow-up being 6 months. Therefore, the authors said, more research is needed to determine treatment effects over a longer period.

Nevertheless, the authors concluded that “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.”

In a linked editorial, Dr. Christian Mallen and Dr. Elaine Hay of Keele University write that this latest study “re-opens the debate” on the effectiveness and safety of paracetamol. They explain that if paracetamol is taken off existing guidelines, it will lead to the increased use of other drugs, such as opioids, and this could present new associated health problems.

Instead, they call for the use of safe and effective alternative treatments, especially non-drug options such as exercise, which have clear benefits in the management of spinal pain and OA.

Source: BMJ; April 1, 2015.

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