A drug to treat Restless Legs Syndrome has become the first to be granted a European licence.
Restless leg can disturb sleep
The condition, a disorder of the nerves, causes a tingling, itching sensation, and unexplained aches and pains in the lower limbs.
It has been estimated that it affects as many as 10% of the population.
The new drug, Mirapexin, has been approved for use by the European Medicines Agency to treat moderate or severe cases.
There are currently no other medications licensed for the treatment of Restless Legs Syndrome (RLS) in the UK.
RLS, also known as Ekbom's syndrome, can affect one or both legs, and symptoms are sometimes felt in the arms as well.
They are most likely to be experienced at night, occasionally meaning the sufferer cannot fall asleep easily, and will often have a strong desire to get up and walk about.
Another symptom associated with RLS are involuntary leg movements, particularly when asleep, which can lead to the sufferer kicking out and waking either themselves or their sleeping partner.
US research found people with diabetes were at particular risk, as were those who did little exercise.
Some symptoms can be relieved by applying heat pads. The condition can also be prevented by cutting down on alcohol and caffeine.
Dr Ray Chaudhuri is a consultant neurologist and head of the National RLS Clinic at King's College Hospital, London - the only specialist clinic of its type in the UK.
He said the lack of sleep associated with restless leg syndrome could have profound implications.
"The disruption can lead to excessive daytime sleepiness, compromised work performance and significantly impact on quality of life.
"The consequences of constant sleep interruptions can be devastating for some people, as the tiredness and lack of concentration can led to depression.
"There is a real need for effective treatments and the introduction of Mirapexin is very welcome news for patients more severely affected by the condition."
However, Dr Chaudhuri said only around 500,000 of the estimated 4m sufferers in the UK were likely to benefit from the drug.
He said doctors currently treated the condition with a range of drugs, but none of these had been licensed.
Some doctors were reluctant to use these medications, as they were used, in much bigger doses, to treat Parkinson's patients.
Mirapexin, produced by Boehringer Ingelheim, is unlikely to be considered by the NHS drug watchdog, the National Institute for Health and Clinical Excellence, for at least a year.