Paracetamol (acetaminophen) no better than placebo for low back pain

Researchers are questioning the use of paracetamol (the name for acetaminophen frequently used in other countries) for acute episodes of lower back pain or for improving pain levels, function, sleep, or quality of life after finding it fared no better than placebo, a study found.

The Paracetamol for Low-Back Pain Study (PACE) was a double-blinded, randomized trial across 235 primary care centers in Sydney, Australia, from November 2009 to March 2013. Researchers randomized 1,652 individuals (average age 45 years) with acute low back pain in a 1:1:1 ratio to receive up to 4 weeks of regular doses of paracetamol (3 times per day; equivalent to 3,990 mg per day), as-needed doses (maximum 4,000 mg paracetamol per day), or placebo in addition to best-evidence advice on management of back pain. Patients were followed for 3 months.

The primary outcome was the number of days it took to recover from low-back pain, with recovery defined as a pain score of 0 or 1 (on a 0 to 10 pain scale) sustained for 7 consecutive days. Secondary outcomes were pain intensity, disability, function, global rating of symptom change, sleep quality, and quality of life. Funding was provided by the National Health and Medical Research Council of Australia and GlaxoSmithKline Australia. Results appeared early online July 24 at The Lancet.

There were no differences in the number of days to recovery between the groups (adjusted P=0.79). Median time to recovery was 17 days (95% CI, 14 to 19) in the regular group, 17 days (95% CI, 15 to 20) in the as-needed group, and 16 days (95% CI, 14 to 20) in the placebo group (regular doses vs. placebo: hazard ratio (HR)=0.99; 95% CI, 0.87 to 1.14 / as-needed doses vs. placebo: HR=1.05; 95% CI, 0.92 to 1.19 / regular doses vs. as-needed: HR=1.05, 95% CI, 0.92 to 1.20).

Authors wrote that it is too soon to completely dismiss paracetamol as a treatment, because it has a favorable safety profile compared to other analgesics such as nonsteroidal anti-inflammatory drugs.

“Because these other medicines have not been shown to provide additional benefit beyond that of paracetamol, and are only marginally better than is placebo, it is not clear which drug should be preferred for management of low-back pain,” they wrote. “Our results convey the need to reconsider the universal endorsement of paracetamol in clinical practice guidelines as first-line care for low-back pain, and suggest that advice and reassurance, rather than analgesics, should be the focus of first-line care.”

An editorial lauded the study, but added, “Although the findings from this high-quality trial are clear, the content of guidelines should not be changed on the basis of a single trial; more robust and consistent evidence, including verification of the results in other populations, is needed.”