Researchers have found a drug to treat chronic pain in mice, without the usual painkiller side effects of sedation, addiction or developing tolerance.

Whether the compound has the same effect in people remains unknown, but researchers led by Hanns Ulrich Zeilhofer of the University of Zurich in Switzerland are progressing with "cautious optimism," science magazine Nature reported Thursday.

The compound comes from the class of drugs, benzodiazepines, which are widely used for sedation or treatment of anxiety, according to the researchers.

They made the finding while studying why benzodiazepines act on brain pathways involved with pain perception, but are seldom effective at relieving pain.

The researchers first tested diazepam, commonly known as valium, by injecting it into the spines of mice.

The researchers found that diazepam could indeed relieve pain as mice, which either endured a painful injection or had a nerve squeezed to simulate chronic pain, were less bothered if they received the spinal injections.

According to the researchers, the next step is to find drugs that will act the same way in humans but without using spinal injections that require a catheter, which are unsuitable for most patients.

(Agencies via Xinhua News Agency January 18, 2008)