Acetaminophen No More Effective than Placebo for Acute Back Pain

July 28, 2014
Jackie Syrop

Whether taken regularly or as needed, acetaminophen for acute low-back pain was no more effective than placebo in a large randomized trial.

Australian investigators found that paracetamol (acetaminophen) for acute low-back pain was no more effective than placebo in a large randomized trial. They reported similar recovery times with acetaminophen, whether taken regularly or as needed, or placebo. Their study was published online July 24, 2014, in The Lancet.

The Paracetamol for Lowe-Back Paid Study, known as PACE, enrolled 1,643 patients in Australia (mean age was 45 years and slightly more than half were men) and randomized them to a regular treatment group (acetaminophen 3 times daily for a daily dosage of 3990 mg), an as-needed group that could use a maximum of 4000 mg/d, or a placebo group. The medication could be taken up to 4 weeks or until recovery. Naproxen was allowed as a rescue medication. Recovery was defined as beginning on the first day when pain scores were 0 or 1 on a pain scale and persisting for at least a week.

Patients who took acetaminophen on a regular schedule had a median time to recovery of 17 days compared with 16 days for patients taking placebo. Patients who took acetaminophen as needed also had a median time to recovery of 17 days, for a hazard ratio versus placebo of 1.05 (95% Confidence Interval, 0.92-1.19).

"Simple analgesics such as paracetamol might not be of primary importance in the management of acute lower back pain," lead author Christopher Williams, MD, from the George Institute for Global Health at the University of Sydney in Australia, said in a statement. "The results suggest we need to reconsider the universal recommendation to provide paracetamol as a first-line treatment for low-back pain, although understanding why paracetamol works for other pain states but not low-back pain would help direct future treatments."

The trial was limited by the possibility that some patients may have taken medications other than naproxen for rescue, and that patients did not adhere to treatment perfectly in all cases.