New review evidence shows caffeine makes painkillers more effective

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Earlier in the week I wrote about snoring but now, as Stop Snoring Week draws to a close, it’s time too wake up and smell the coffee! For it’s also UK Coffee Week, which focuses on raising money for Project Waterfall, delivering clean water projects in African coffee-producing countries, and I have some good news about caffeine.

Caffeine is often added to common painkillers such as such as paracetamol, ibuprofen and aspirin, in medicines which are available both with and without a prescription. It is added in the belief that the caffeine makes these painkillers more effective, but until now there has been little research evidence to support this belief.

So does caffeine added to painkillers make them work better?

In the light of a new Cochrane review, the simple answer seems to be yes. The reviewers looked for studies comparing the pain-relieving effect of common painkillers with and without added caffeine. As well as searching key databases the authors contacted drug companies known to have carried out trials that have not been published.

19 randomised controlled trials (RCTs) of 7238 people were included, assessing several acute pain conditions including headache, post-dental pain, postoperative pain following childbirth, and period pain. Most studies used paracetamol (500 mg to 1500 mg) or ibuprofen (100 mg to 400 mg), with two using aspirin (650 mg and 800 mg), one aspirin (500 mg) plus paracetamol (400 mg), one diclofenac (100 mg), and one tolfenamic acid (200 mg). Caffeine was added at doses of 50 mg to 260 mg, with most studies using between 100 mg and 200 mg. In most studies participants were not allowed to have any caffeine in food, drink or other medicines for a specified time within the trial.

Here’s what they found:

  • There was a small but statistically significant benefit with caffeine used at doses of 100 mg or more for all pain conditions and painkillers. About 5% to 10% more people achieve a good level of pain relief with the addition of caffeine
  • There was only one serious health event in one person treated with caffeine plus painkiller and this was not considered related to the study medication
  • Most of the studies were old, with only three (in headache) published since 2000, but they were generally of good methodological quality
  • There are 20 more studies with over 9000 participants for which data for analysis were not obtainable. However, even if all the missing data showed no effect of caffeine, the additional effect of caffeine would still be statistically significant

The authors concluded that the existing evidence is probably sufficient to support the use of caffeine with analgesics, with the addition of ≥ 100 mg caffeine to a standard dose of commonly used analgesics providing a small but important increase in the proportion of people who experience a good level of pain relief.

100mg of caffeine is roughly equivalent to the caffeine in a mug of coffee. So if you’ve got a headache and have standard painkillers in the cupboard, you may do well to wash them down with a coffee.

Links:

Derry CJ, Derry S, Moore RA. Caffeine as an analgesic adjuvant for acute pain in adults. Cochrane Database of Systematic Reviews 2012 Issue 3. DOI: 10.1002/14651858.CD009281.pub2

Cochrane summary and podcast of this review

Review author Dr Andrew Moore from the Pain Research Unit at the Churchill Hospital in Oxford talked to Dr Mark Porter on BBC Radio 4, about which over the counter painkillers are likely to work best for acute pain, including evidence from this review. You can listen to the broadcast or read the transcript at Inside Health (10th April 2012).