Taking paracetamol with a mug of coffee is often recommended by experts as an effective way to tackle a headache.
Now a trial is under way comparing the effectiveness of a combined paracetamol and caffeine pill against ibuprofen for the treatment of tension-type headaches.
Around 300 people are taking part in the trial at Parexel International, a U.S. clinical research organisation.
Those having the active treatment will take capsules containing 500 milligrams of paracetamol and 65mg of caffeine (the amount found in an average mug of coffee). Caffeine is a weak stimulant, which may boost the effect of paracetamol.
In a study carried out at Oxford University, researchers found that combining paracetamol with 100mg or more of caffeine helps relieve pain in 10 per cent more people.