Evidence
Alert

Paracetamol is a weak painkiller for regular tension headaches

Paracetamol is only slightly more effective than dummy tablets (placebo) at relieving pain in people who experience regular tension-type headaches.

A Cochrane review found that 24 out of 100 people who took paracetamol for regular tension-type headaches were pain free at two hours, compared with 19 out of 100 who took an inactive placebo.

There was no difference in risk of side effects between paracetamol and placebo.

Paracetamol is a cheap drug that is readily available over-the-counter. Because serious side effects are so uncommon and the “placebo effect” is so strong, this drug could be considered as an option for treating regular tension-type headache for people who find that it helps them.

However, clinicians treating regular tension-type headache may consider alternatives and patients should be made aware that sustained use of paracetamol may cause medication overuse headache.

Why was this study needed?

Tension-type headache is the most common type of headache, affecting 21% of people worldwide. These headaches are characterised by pressing or tightening pain (non-pulsating) of mild-to-moderate intensity on both sides of the head.

Frequent episodic tension-type headache is diagnosed when the person has between two and 14 headaches a month. People with frequent tension-type headaches may struggle to concentrate and take more time off work.

Sometimes tension-type headaches get better without treatment, but many people take over-the-counter painkillers as a first treatment.

Paracetamol is a readily available and cheap over-the-counter painkiller, with two tablets (1,000 mg) the most common dose. A systematic review was needed to compile the available evidence on the safety and effectiveness of paracetamol for reducing acute pain in tension-type headache.

What did this study do?

This Cochrane systematic review identified 23 randomised controlled trials assessing the effectiveness and safety of paracetamol in 8079 adults with frequent tension-type headache.

Trials had to have compared paracetamol (taken by mouth) with an inactive placebo, although many also compared paracetamol with another active drug. Trials also had to be double blind, with neither participants nor assessors aware of the treatment given.

The main outcome of interest was whether participants were free from pain two hours after taking paracetamol or placebo.

Most trials were at high or unclear risk of bias, largely because of inadequate reporting of outcomes and lack of clarity on how participants were randomised. Most trials were published before 2000, and the countries and settings were not reported.

What did it find?

  • Pooled analysis of eight high quality studies found that a single 1,000 mg dose of paracetamol was slightly more effective at relieving pain than placebo. Paracetamol stopped pain within two hours in 24 in 100 people, whereas placebo stopped pain in 19 in 100 people (relative risk (RR) 1.3 (95% confidence interval [CI] 1.1 to 1.4).
  • This meant that 22 people with tension-type headache would need to be treated with 1,000 mg paracetamol instead of placebo for one person to be pain free at two hours.
  • The broader outcome of being pain free or having only mild pain at two hours was achieved by 59 out of 100 people taking paracetamol compared with 49 out of 100 taking placebo (RR 1.2 (95% CI 1.15 to 1.3).
  • There was no difference between paracetamol or placebo in the number of people experiencing side effects, which affected around 1 in 10 people. Side effects were mostly mild, and no participants had serious side effects.
  • Paracetamol 1,000 mg was about as effective as ibuprofen 400 mg, with 33 in 100 people pain free at two hours with paracetamol and 38 in 100 with ibuprofen. This analysis used three low quality trials and results should be treated cautiously.

What does current guidance say on this issue?

The 2012 NICE guideline on diagnosis and management of headaches (currently being updated) recommends considering aspirin, paracetamol or a non-steroidal anti-inflammatory drug, such as ibuprofen, for acute treatment of tension-type headache. The treatment choice should take into account the person’s preference, other illnesses and risk of adverse events.

The guideline adds that healthcare professionals should be alert to the possibility of medication overuse headache in people whose headache developed or worsened while taking paracetamol on at least 15 days per month over a period of three months or more.

What are the implications?

This review suggests that paracetamol has a minimal effect on relieving pain in people with frequent tension-type headache compared to placebo.

However, the drug is very cheap and available over-the-counter, which is of importance to patients given that many with this type of headache do not seek medical help.

Paracetamol also had a low rate of side effects. Therefore, paracetamol remains an option for people with frequent tension-type headaches who find that it helps.

 

Citation and Funding

Stephens G, Derry S, Moore RA. Paracetamol (acetaminophen) for acute treatment of episodic tension-type headache in adults. Cochrane Database Syst Rev. 2016;(6):CD011889.

Cochrane UK and the Pain, Palliative and Supportive Care Cochrane Review Group are supported by NIHR infrastructure funding.

 

Bibliography

NHS Choices. Tension-type headaches. London: Department of Health; 2015.

NICE. Headaches in over 12s: diagnosis and management. CG150. London: National Institute for Health and Care Excellence; 2012.

NICE. Clinical Knowledge Summary. Headache - tension-type. London: National Institute for Health and Care Excellence; 2015.

Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre

 

Definitions

Tension-type headache is a common, mild and self-limiting type of headache. It can be divided into three types: infrequent episodic (less than one headache per month), frequent episodic (two to 14 headaches per month) and chronic (15 headache days a month or more).

The International Headache Society recommends that controlled trials of drugs in tension-type headache should use a pain-free rate at two hours as the main outcome measure. Only eight of the 23 studies included in this Cochrane review reported this recommended outcome. The other studies reporting pain relief at other time points, such as one hour or four hours after dosing, or reduction in pain.

 

Commentaries

Expert commentary

The data suggests that paracetamol is relatively ineffective for frequent episodic tension-type headache. We do not know how well it might work for infrequent headaches, or whether some people might consistently respond to treatment. Regular use of paracetamol can lead to medication overuse headache. Perhaps we need to advise no more than very occasional use of paracetamol for headaches, and only then if the patient consistently experiences benefit.

Professor Martin Underwood, Director, Warwick Clinical Trials Unit, Warwick Medical School, The University of Warwick