Doctors didn't warn women of 'risky sex' drug urges

Claire says she began leaving her house in the early hours of the morning to cruise for sex. Wearing a see-through top and jacket, she would flash her chest at any man she could find. She did this regularly, she says, and in increasingly dangerous locations, despite having a partner.

"There remains an element in your head that knows what you're doing is wrong, but it affects you to the point that you don't know you're doing it."

Claire says it took years to connect these urges with her medication - and they disappeared almost immediately when she stopped taking it. She feels complete "shame" and is "mortified" at the danger she placed herself in.

Impulsive behaviours, including gambling and increased sex drive, have long been listed as side effects in medicine leaflets for dopamine agonist drugs - and are thought to affect between 6% to 17% of RLS patients taking them, according to health guidance body NICE. A "common" side effect of any medicine is considered to only affect 1% of people who take it, according to the NHS.

The drugs work by mimicking the behaviour of dopamine, a natural chemical in our brains which helps regulate movement. It is known as the "happy hormone" because it is activated when something is pleasurable or we feel rewarded.

But agonist drugs can over-stimulate these feelings and under-stimulate the appreciation of consequences - leading to impulsive behaviour, according to academics.

The cases of what the GSK report from 2003 described as "deviant behaviour" involved two men who were prescribed Ropinirole for Parkinson's disease. In one, a 63-year-old-man sexually assaulted a seven-year-old girl, leading to a custodial sentence.

The documents said the perpetrator's libido had increased significantly from the start of his treatment with Ropinirole and his "libido problem subsequently resolved" after his dose was reduced.

In the second case, a 45-year-old man carried out "uncontrolled acts of exhibitionism and indecent behaviour". His sex drive was reported to have increased prior to being prescribed Ropinirole but his urges "intensified" after the treatment.

Prevalence rates of what GSK calls "deviant" sexual behaviours caused by the drugs are unknown and tend to be under-reported by those who experience them, according to Valerie Voon, a professor of neuropsychiatry at the University of Cambridge.

"There's a lot of stigma and shame attached to it, and people don't realise that it's associated with a medication," she says.

Prof Voon believes risky sexual behaviours - beyond a purely increased libido - should be specifically warned about and screened by the NHS, because their impact can be "devastating".