By JAYA NARAIN

Last updated at 11:56 30 January 2008

A devoted father turned into a gambling addict and ran up £90,000 in debts after doctors prescribed him a drug to treat his Parkinson's disease.

Paul McGarvey was 34 when he was diagnosed with the progressive and incurable neurological condition 18 years ago.

In 1997 as his condition worsened, doctors prescribed Pergolide - when, he claims, "a switch flicked in his head" turning him from a responsible family man into a compulsive gambler.

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He had never placed a bet in his life before taking the drug, but quickly became obsessed with gambling and lost up to £250 a day in his six years on the prescription.

Mr McGarvey, 52, a father of three from Kirkby, Merseyside, said: "I just changed overnight. I started taking the tablets and started going into the betting shop at the same time.

"I never even had a bet on the Grand National before - I was hard-working and always regarded gambling as a mug's game.

"Then I got prescribed this drug and I turned into someone else. It was like having a switch turned on and I became driven to gamble.

"I ran up debts on credit cards and took out bank loans. I borrowed off friends and family and lied and cheated to make sure I could gamble."

Rita, his wife of 30 years, said: "I found slips from when things had been pawned. Then we started getting hundreds of pounds in bank charges every month because there were direct debits coming out that there was no money to pay - now we've got about £90,000 of debt."

Mr McGarvey, a former tiler who had been earning more than £50,000 a year, was paying just £57 a month towards his mortgage and was due to pay it off this year.

Now the couple have consolidated their debts and have a mortgage of £500 a month until 2023.

When he was taken off Pergolide after six years, his gambling addiction disappeared and he made the connection.

Mr McGarvey said: "Now they have warnings on the bottle explaining that a side-effect can be addictive behaviour.

"Doctors told me that they had banned the drug in the United States. It's scandalous that it was being prescribed here."

The manufacturer, Lilly, agreed to withdraw the drug from the U.S. market last year after several published studies revealed a link between the drug and increased rates of heart problems. Mr McGarvey is taking legal action against Lilly and wants to contact others who suffered similar reactions.

Pergolide is thought to over-stimulate receptors in the brain which can lead to gambling addiction. Other patients can become sex addicts.

Lilly says that pathological gambling is a known but very rare side-effect of taking Pergolide.

Dr Kieron Breen, from the Parkinson's Disease Society, said: "It is estimated that up to 14 per cent of people who take this class of drug will have some form of compulsive behaviour."