There is no cure for irritable bowel syndrome (IBS) - but a new drug could be the first to offer genuine relief to many.

However, although it is available now for patients in the US, people in the UK will have to wait at least until the end of the year until it is licensed here.

A study into alosetron, marketed under the brand name found that more than 40% of women given the drug achieved "adequate" relief from the abdominal pain associated with IBS.

IBS involves not only pain, but also diarrhoea, or diarrhoea alternating with constipation.

Sufferers often desperately need to go to the toilet with little warning, which severely limits their lifestyle.

The new drug, produced by Glaxo Wellcome, was licensed for use in the US last month.

Scientists are excited because it is the first in a whole new class of drugs aimed at relieving IBS.

Could get better

Once it is refined and targeted at the right patients in future, it could become even more effective.

The study, published in The Lancet, tested it only on women - although it is likely to work for men as well.

Approximately 650 women were given either alosetron or a placebo - a dummy tablet containing no drug.

The treatments lasted three months, and 41% of those taking the drug reported relief for the entire three-month period.

Other studies have shown more than 60% experiencing relief, though not necessarily throughout the trial period.

Dr Robin Spiller, a reader in gastroenterology at University Hospital Nottingham, said: "It's definitely effective - a real advance.

"The medical community is getting excited about this new class of drugs."

He said that if doctors could find out why the drug worked for some and not for others, then it could be made even more effective.

No-one knows what causes IBS, although it is suggested that stress can make it worse.

Most sufferers are advised to try to manage the condition by changing their diet and trying to reduce stress levels, as well as taking other medication.