Medical Matters: Don’t turn your back on paracetamol just yet

For all the lengthy testing undertaken on new treatments, there are even more established interventions in medicines that are simply taken as gospel. These treatments make intuitive sense based on existing science, with physicians confirming their value from practice experience.

However, when it comes to the ultimate test of a randomised, double-blind controlled trial, surprisingly few established treatments have been put through this particular hoop.

Nonetheless, the recent headline “Paracetamol used to treat acute lower back pain is no better than a dummy pill” came as a major shock. As it is the go-to over-the-counter remedy for many causes of acute pain, and as a drug with relatively few side effects when used correctly, this is a surprise.

The study behind the headlines was carried out by researchers from the University of Sydney, the University of New South Wales and the University of Newcastle, Australia, and was published in the Lancet.

Well designed, it was a double- blind randomised controlled trial looking at the effectiveness of paracetamol in improving recovery time from acute back pain, compared with a placebo (dummy pill).

In other words, it used the best kind of scientific study when it comes to assessing the effectiveness of healthcare treatments.

The researchers recruited 1,652 people with acute lower back pain from 235 primary care centres across Australia. To be included, patients had to be suffering a new episode of acute lower back pain (defined as shorter than six weeks’ duration and preceded by one month with no pain). People suspected of having a serious spinal disease or who were already regularly using painkillers were excluded from the trial.

Pain relief

Participants were asked to take two tablets three times a day from a sealed “regular” box of prepared medication and had access to a sealed “as required” box for additional pain relief.

They were randomised to one of three treatment groups: a “regular” box of paracetamol (the equivalent of 3,990mg daily) and a placebo “as required” box; a “regular” placebo box and an “as required” paracetamol box (maximum of 4,000mg daily); or placebo pills in both boxes.

Asked to continue their allotted treatment until they had recovered, patients in the study recorded pain scores in a daily pain and drug diary.

Researchers then looked at recovery times (measured in days) and also assessed pain intensity, disability, sleep quality and quality of life.

The results were striking: at 16-17 days there was no significant difference in the number of days to recovery in the three groups.

Nor did paracetamol have any statistically significant effect on short-term pain levels, disability, function, sleep quality or quality of life. All in all, a pretty damning indictment of the effectiveness of paracetamol in the treatment of acute back pain.

Lead author Dr Christopher Williams of the University of Sydney concluded: "The results suggest we need to reconsider the universal recommendation to provide paracetamol as a first-line treatment for low-back pain."

However, before experts begin to rewrite practice guidelines for the treatment of acute low-back pain, the findings need to be replicated in one other well-designed clinical trial.

Another caveat is the access participants had to other treatments such as physiotherapy during the research.

In addition, the fact that no patients had to take time off work may indicate that the severity of pain in those studies was at the mild end of the spectrum, thereby limiting the relevance of the research.

Ubiquitous painkiller

It is important to point out that this questioning of paracetamol’s efficacy is limited to the treatment of lower back pain, so the ubiquitous painkiller still has an unquestioned role in treating headache and toothache. Meanwhile, its effectiveness as a treatment for fever and muscle ache in influenza and other viral illnesses remains unchallenged.

However, for those of us prone to episodes of acute lower back pain, the best advice may be, in the tradition of that second World War rallying cry, to “Keep Active and Carry On”.

mhouston@irishtimes.com muirishouston.com