Paracetamols.

Findings contradict doctor's recommendations: Study shows paracetamol ineffective for back pain. Photo: Dominic O Brien

Paracetemol has been found to be no more effective for back pain than a placebo, a study has found.

The findings contradict the first line recommendation of doctors for managing back pain and the packaging advice of paracetemol manufacturers.

They startled the University of Sydney researchers who undertook the study upon discovering that there had never been a large-scale trial comparing paracetamol to placebo for back pain.

Back-pain treatment guidelines universally recommend paracetemol as an analgesic.

Panadol sells a product that is dedicated to back and neck pain, containing 500g paracetamol.

"Patients often said, 'I've tried paracetamol and it doesn't seem to work'," said Chris Maher, a professor at the University of Sydney's George's Institute for Global Health.

"We thought at the time that maybe they were dosing inadequately."

The patients who participated in the trial were split into those who took a placebo, those who took paracetamol whenever they felt pain and a third group that took the medication three times a day. 

The researchers expected only to notice an improvement among the third group.

"But we were surprised to see that no matter how you took paracetamol, it made no difference."

The annual medical bill for back pain is $4.8 billion, according to Arthritis and Osteoporosis Victoria. 

The condition is also rated by the World Health Organisation as Australia's most burdensome disease, alongside heart disease.

But many of the recommended treatments have been found to be ineffective or risky.

Steroid injections, which doubled in Australia between 2001 and 2011, were discredited in the New England Journal of Medicine earlier this month as no more effective than a placebo.

Professor Maher said Medicare spends an annual $220 million on imaging such as MRI scans and X-rays, despite treatment guidelines discouraging the practice.

Often such scans exposed conditions that were not causing the pain, which prompted patients to pursue useless treatment regimes.

"I think the burden [of back pain] is becoming worse because we're overcomplicating management," Professor Maher said.

Among the patients who participated in the paracetamol trial, which was published in The Lancet on Thursday, about half recovered within two weeks.

"It's become accepted wisdom because paracetamol has been used for pain and fever for a long time and people thought if it works for dental pain and headaches it perhaps works for back pain.

"People used to think that paracetemol was the most important thing and if you get a chance in passing talk to your patient about doing physical activity.

"This study would suggest that probably the most important thing a patient does is to resume normal activities."

It was not clear from the study why paracetamol did not work for back pain.

The trial involved 1643 people with acute uncomplicated low back pain.