PATIENTS with multiple sclerosis and Parkinson's disease who suffer from chronic sleepiness may benefit from a relatively new drug which has just received a wider UK licence.

Developed a few years ago, the drug Provigil (modafinil) could only be used for patients with narcolepsy and obstructive sleep apnoea syndrome until now. But UK licensing authorities have agreed to allow it to be prescribed by doctors for excessive sleepiness linked with chronic medical conditions.

It is thought that up to six per cent of adults suffer from excessive sleepiness. Factory workers who have serious difficulties adjusting to night-time working and find it difficult to stay awake, could also benefit under the new rules.

Dr Paul Reading, a consultant at the regional neurosciences centre at Newcastle General Hospital, who already treats around 140 patients for narcolepsy, a condition in which patients find it impossible to stay awake during the day, welcomes the rule relaxation.

"People with neurological conditions such as MS and Parkinson's disease often find the inability to stay awake to be one of their most disabling symptoms. Provigil provides a welcome treatment option that is effective, well-tolerated and can significantly improve patients' quality of life," says Dr Reading.

The consultant neurologist says there are many applications for the drug, including the possibility of using it for terminally ill patients being treated with sleep-inducing opiates such as morphine.

"Potentially there is a huge market for this drug. It works, it is long acting and after six years, there are no reported problems."

Another group of patients who might be able to benefit from Provigil are those who experience excessive sleepiness as a side-effect from other prescribed drugs, including some people being treated for schizophrenia.

Unlike amphetamine, a drug which has been abused for recreational purposes by revellers who want to stay wide awake, Provigil appears to be safe, says Dr Reading. But he thinks it unlikely that Provigil will be used illegally in this way. "Its a lot more expensive than Red Bull," he jokes.

Provigil, made by the American firm Cephalon, works by selectively stimulating areas of the brain believed to be associated with regulating wakefulness.