A new treatment for migraine that is as effective as existing drugs but with fewer side effects will bring fresh hope to millions of sufferers, scientists said yesterday.

Improved understanding of the mechanism that causes the brain to over-react to stimuli has led to the development of a drug that works in a different way from existing treatments.

Migraine affects an estimated six million people in Britain – 15 per cent of the adult population – and runs in families. It is caused by an "oversensitive" brain which reacts to triggers such as fatigue, hunger, stress or the weather with a throbbing, one-sided headache, often accompanied by nausea and visual disturbances. It affects three times more women than men.

The new drug, called telcagepant, is a rescue treatment that interrupts the sequence of chemical reactions in the brain that cause the migraine at a different point from existing drugs.

A final trial of the drug, published in The Lancet today, showed it reduced pain and was better at preventing the return of the migraine over 24 hours than zolmitriptan, an existing triptan drug. However, the improvement was not statistically significant.

The main advantage of telcagepant was reduced side effects. Triptans can cause a tight chest and throat, dizziness, numbness of skin and is thought to have a potential constricting effect on the blood vessels. As a result, patients with heart disease and high blood pressure are advised not to take it.

Telcagepant does not appear to have the same vasoconstricting (blood vessel narrowing) properties, but heart patients were excluded from the trial. The study was conducted among 1,380 patients in 81 hospitals in the US and Europe, led by Tony Ho of Merck Research Laboratories, Philadelphia.