Dealing with pain, or is it?

The jury is out on the efficacy of paracetamol for reducing pain in many conditions, new Australian research reveals 

For most conditions, evidence regarding the effectiveness of paracetamol is insufficient for drawing firm conclusions, Australian researchers have concluded.

A systematic review of 36 previous systematic reviews found evidence for paracetamol’s efficacy in four conditions was moderate to strong, but also found strong evidence that paracetamol is not effective for reducing acute low back pain.

Investigations that evaluate more typical dosing regimens are required, the authors concluded.

High or moderate quality evidence that paracetamol (typically 0.5–1 g, single or multiple doses) is superior to placebo for relieving pain was available for only four of 44 painful conditions examined, the review’s authors concluded. 

They found there was high quality evidence that paracetamol provides modest pain relief for people with knee or hip osteoarthritis and after craniotomy.

There was also moderate quality evidence for its efficacy in tension‐type headache (a 30% increase in patients who were pain‐free at 2 hours) and perineal pain soon after childbirth (with more than twice as many patients experiencing 50% pain relief).

The effect sizes were modest, particularly for patients with knee or hip osteoarthritis or tension headache.

The review found there was “high quality evidence that paracetamol is not effective for relieving acute low back pain”, while evidence regarding efficacy in other conditions was of “low or very low quality”.

Frequency of adverse events was generally similar for people receiving placebo or paracetamol, except that transient elevation of blood liver enzyme levels was more frequent during repeated administration of paracetamol to patients with spinal pain. 

However, most studies evaluated the immediate effects of single doses of paracetamol, which does not reflect typical clinical use.

The findings called into question much of the existing reasoning for the clinical use of paracetamol, the authors said.

“While paracetamol is widely used, its efficacy in relieving pain has been established for only a handful of conditions, and its benefits are often modest. Although some trials have evaluated regimens that may have underestimated its utility, the clinical application of paracetamol is primarily guided by low quality evidence, at best”.

The authors, from the University of Sydney and St Vincent’s Hospital said the review highlights the need for large, high quality trials to reduce uncertainty about the efficacy of paracetamol for relieving common pain conditions.

“Available evidence is largely derived from trials that evaluated the effects of single doses; investigations of multiple dose regimens, reflecting usual practice, are needed,” they said.

“For some long term conditions, such as osteoarthritis, long term efficacy and safety should also be evaluated”.

The research was published online first in the MJA


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