Hundreds of thousands of traumatic brain injury deaths could be avoided by using a drug that costs less than £7, research has suggested.
London School of Hygiene and Tropical Medicine scientists tested transexamic acid (TXA) on almost 13,000 patients.
Results published in The Lancet journal found giving patients TXA within three hours slashed the number of fatalities by as much as 20 per cent.
The drug - already used to save the life of stab victims - stops bleeding in the brain by preventing the breakdown of blood clots.
Scientists from the London School of Hygiene and Tropical Medicine believe transexamic acid (TXA) could save hundreds of thousands of lives
By stopping bleeding into the brain by preventing the breakdown of blood clots, the drug might prove invaluable to head injury sufferers
Survival rates were almost a quarter higher in patients with mild and moderate traumatic brain injuries who were given TXA.
But it provided no clear benefit in the most severely injured patients.
However, the largely encouraging results from the drug - to which the trial found no risky side-effects - have exciting implications for the advancement of medicine.
Professor Ian Roberts, who co-authored the study, said: 'We already know that rapid administration of tranexamic acid can save lives in patients with life-threatening bleeding in the chest or abdomen such as we often see in victims of traffic crashes, shootings or stabbings.
'This hugely exciting new result shows that early treatment with TXA also cuts deaths from head injury.
'It's an important breakthrough and the first neuroprotective drug for patients with head injury.
A global randomised trial of 12,737 head injury patients by the London School of Hygiene & Tropical Medicine found TXA could cut the number of fatalities by as much as 20 per cent
'Traumatic brain injury can happen to anyone at any time, whether it's through an incident like a car crash or simply falling down the stairs.
'We believe that, if our findings are widely implemented, they will boost the chances of people surviving head injuries in both high-income and low-income countries around the world.'
Patients were recruited from 175 hospitals across 29 countries.
A common complication of TBI is bleeding around the brain, which can lead to brain compression and death.
Patients with very severe head injuries are unlikely to benefit from tranexamic acid treatment because they often have extensive brain bleeding prior to hospital admission and treatment.
But the study found a substantial benefit in patients with less severe injuries who make up more than 90 per cent of TBI cases.
Professor Ian Roberts of the London School of Hygiene & Tropical Medicine hailed the findings 'hugely exciting'
Professor Antoni Belli of trauma neurosurgery at the University of Birmingham and co-investigator for the trial, said: 'This is a landmark study'