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Acetaminophen Found Ineffective for Treating Low Back Pain

August 5, 2014
When compared with placebo, acetaminophen had no beneficial effect on recovery time, pain improvement, or disability. The study findings call into question the widespread use of acetaminophen for low back pain.

Doctors commonly recommend acetaminophen as a first-line treatment for many types of aches and pain, but a new study finds the drug may be wholly ineffective in aiding patients with acute low back pain.

The study, published online in The Lancet, found acetaminophen, whether administered on a scheduled regimen or as needed, had no discernible effect on recovery time, pain improvement, or disability when compared to a placebo.

These new findings could have a significant impact on pain management, as the researchers said they now "question the universal endorsement of [acetaminophen]" for acute low back pain (LBP) patients.

"People have generalized trial results from similar conditions and presumed that if paracetamol [acetaminophen] worked for headache and toothache it should also work for back pain," said study author Chris Maher, PhD, of the George Institute for Global Health at the University of Sydney, Australia. "We know from our trial that this is not true."

It is no surprise to see that acetaminophen is a poor agent for low back pain. There are many anti-inflammatories and analgesics that practitioners routinely select over acetaminophen.  One has to wonder why it is even in guidelines today except possibly for its cheaper costs. One problem with this study  is that it may give some practitioners the erroneous impression that low back pain is best treated with a single, evidenced-based pharmaceutical. 

Low back pain should be aggressively and simultaneously treated with multiple therapies that can include stretching exercises, analgesics, anti-inflammatories, topical agents, electromagnetic devices, homeopathy, and prolotherapy. What is not good practice is treating low back pain with a single pharmaceutical agent or an epidural corticoid injection until a multi-faceted approach has been attempted and failed. 

Clues to Back Pain

Dr. Maher also said that the study provided some clues into low back pain etiology. "This pattern of results suggests that the mechanisms of back pain are probably different to the mechanisms of headache and toothache," Dr. Maher said.

Lead author of the study, Chris Williams, MD, told Practical Pain Management that this is the first study to compare paracetamol with placebo for treatment of low back pain. "The role of paracetamol in managing musculoskeletal pain has probably been over stated in practice guidelines," Dr. Williams said. He also noted that acute LBP sufferers are often prescribed medications that prevent them from maintaining normal activity. "Unfortunately, other studies have shown most patents miss out on receiving advice about this," Dr. Williams said.

Analyzing 1,652 patients culled from 235 care facilities throughout Sydney, Australia, the team randomly designated the patients into 3 equal groups. With both patients and staff blinded to the study design, subjects received daily doses of paracetamol (3,990 mg), as-needed doses (maximum of 4,000 mg), or a placebo. In Australia and the United Kingdom, acetaminophen is referred to as paracetamol.

After receiving 4 weeks of drug therapy and 12 weeks of individual care and advice, researchers measured how long it took the patients to recover from their acute back pain. Doctors measured pain using the visual analog scale (0 no pain, 10 worst pain). 

All three groups recorded similar median times for recovery; the placebo group took 16 days to recover, while the regular-dosing and as-needed paracetamol groups took 17 days. Like recovery times, all of the groups had similar rates of patients reporting adverse events, at around 19% for each group.

Researchers also found that patients taking the drug showed no positive differences from the placebo group in their sleep, quality of life, or disability level.1

Similar studies have been done in the past, however, that provide evidence of acetaminophen's efficacy for treating low back pain, although they have notable differences from Drs. Maher and William's research.

For example, some studies used a combination analgesic (tramadol and acetaminophen) for treating chronic pain, not acute, and the dosing methods and patient evaluation procedures differed, since they were aimed at managing pain levels in chronic LBP patients, not aiding recovery time in acute LBP patients.2,3

McNeil Consumer Healthcare, the manufacturer of Tylenol, said in a statement that they "encourage (the) ongoing study" of OTC medications, but also assert that the "safety and efficacy profile of acetaminophen" has been backed up by past research.

Back Pain More Complex

While some practitioners have commented publicly their incertitude over The Lancet study's claims, others agree that paracetamol's efficacy for acute LBP should be reevaluated. "As a physician, there's more to it than just taking (acetaminophen) alone," said Mike Flippin, MD, an orthopedic surgeon based in San Diego, California. "Back pain is obviously much more complex."

"I would encourage practitioners to read the trial because back pain is such a common condition and the trial results are so clear," Dr. Maher said. "This is a trial that will require many clinicians to rethink how they currently manage back pain."

One study published in Spine gives corroborating research to Drs. Maher and William's findings; the study concluded that low-level heat wrap therapy treated acute LBP patients better than acetaminophen or ibuprofen.4

The researchers also showed that  patients under close practitioner supervision and care tended to recover more quickly. "Probably the most important part of care for patients with acute low back pain is for the clinician to reassure a patient that they will recover and guide their return to normal activities," Dr. Maher said.

Past research backs up these claims. A study published in The New England Journal of Medicine concluded that acute LBP sufferers had slower recoveries when prescribed bed rest than if they were encouraged to resume light exercise and resume normal daily functioning, within reason.5

"Patients with low back pain are naturally apprehensive about moving because it is so painful, and they are concerned for the future." Dr. Maher said. "A wise and skilled clinician can turn this around and really assist a patient on the road to recovery."

The study was funded by the National Health and Medical Research Council of Australia and GlaxoSmithKline Australia, an Australian-based pharmaceutical company.


Last updated on: August 18, 2014