Scientists at the University of Virginia in the US found that it could knock an average of three and a half days off a two-week cold.

They tested the drug - pleconaril - on 1,024 people aged 14 and over who were suffering a cold.

Patients who got the drug suffered the illness for an average of 11.5 days, compared with 14 days for those given dummy pills.

'Safe drug'

Dr Frederick Hayden presented his team's findings at the Interscience Conference on Antimicrobial Agents and Chemotherapy in San Francisco.

He said the drug seemed very safe, with patients in both groups experiencing the same side effects, such as diarrhoea and stomach cramps.

The patients were suffering viral respiratory infections - a serious form of the common cold that causes fevers, coughs, muscle aches, tiredness and a runny nose.

It can also cause ear infections and develop into bronchitis.

Other studies have shown that the drug is effective at cutting the course of a viral meningitis infection by two to three days, and it is currently in the second major phase of clinical trials to evaluate its effectiveness at treating the disease.

It has one more stage to go before it can be approved for general use.

Latest development

The research contributes to a growing body of evidence suggesting that a cure for the common cold may be possible, although it remains a long way off.

In May this year, researchers announced that they could disrupt one of the viruses behind the disease before it took hold on the body.

However, there were concerns that the method used - spraying an artificially-produced molecule into the nose and throat - might have toxic effects.

A medical solution to the common cold has been impossible to find mainly due to the high numbers of constantly changing viruses. There are at least100 different types of rhinovirus.