‘Strange’ side-effects to Parkinson’s drug

We often expect to see common side-effects such as nausea and drowsiness when reading the consumer information leaflet accompanying most drug packaging; but when more sinister side-effects arise, alarm bells may start ringing.

A treatment for Restless Legs Syndrome and Parkinson’s Disease has long been in the spotlight for its devastating alleged side effects, which may include compulsive behaviours such as pathological gambling and sex addiction.

The drug, Permax, is said to trigger compulsive behaviours in some people, with one woman claiming she “gambled away everything” and ended up living on the street after taking the drug for a decade to treat her restless leg disorder; a neurological disorder causing odd sensations in the limbs and jerking of the legs.

She also claims her marriage and relationship with her children broke down under the strain; and her former husband alleges as soon as she stopped taking the drug, she stopped gambling. Is this a coincidence or something more sinister?

Permax is a type of drug called a “dopamine agonist”, restoring the imbalance of the dopamine which controls the body’s movement; and also turns on the reward centres in the brain. Another drug commonly prescribed to treat symptoms of Parkinson’s disease, Cabaser, works in the same way.

It was not until 2005 that the distributors of Permax warned doctors about “compulsive, self-rewarding behaviour (that is pathological gambling) and libido increase” that could come with taking the drug. The following year, Pfizer Australia issued precautionary statements to doctors with similar warnings about Cabaser’s potential adverse side effects.

However, it allegedly took another two years for the warnings to be listed in the consumer information inserted in the drug packaging.

More than 100 litigants have now joined a class action against the two drug companies that market Permax and Cabaser in Australia. Lawyer Anne Shortall, from Melbourne firm Arnold, Thomas & Becker, says similar lawsuits against other pharmaceutical companies have been filed overseas.

Ms Shortall says previous court action in the United States has revealed some drug companies may have known about the link between dopamine agonists and behaviour disorders as far back as 1984.

“At this stage of the proceedings we haven’t had discovery of all the relevant documentation. So we’re not quite sure exactly what trials were undertaken, but certainly as a result of the medical journal articles raising this issue, the drug company should have been aware of it and undertaking testing.

“A number of countries overseas had issued warnings. Certainly in Holland there had been a warning inserted into the medication. What we’re saying is that a warning should have been inserted a lot earlier,” she says.

Researchers at the University of Sydney are also in the early stages of conducting an investigation into the link between compulsive behaviours, namely gambling, and Parkinson’s medication.

Chief investigator, Professor Alex Blaszczynski, told DPS eNews there has been a number of previous studies that show increases in problem gambling and Parkinson’s medication, with research indicating a 9% prevalence.

“What we’re exploring now is to see if a link in compulsive behaviours and Parkinson’s medication is pre-existing or whether the behaviours are new,” Professor Blaszczynski says.

While he wonders if it is a “bit too early to make any claims”, he admits he has doubts in suggestions of the link between compulsive behaviours and Parkinson’s medication.

“In my clinical judgement, a few Parkinson’s patients who were examined had a history of gambling before being diagnosed with Parkinson’s. They began gambling to try to ease the financial burden of the costs of treatment associated with their disease… but I’m open to persuasion,” Professor Blaszczynski says.

The study is expected to be completed by the end of the year. DPS eNews will have a follow-up story indicating the results of Professor Blaszczynski’s research towards the year’s end.

Did you know…

A paper published this year by the Mayo Clinic in the US reported a staggering 22% of patients with Parkinson’s disease who take dopamine agonists developed impulse control disorders.

If you or a loved one has Parkinson’s disease, share your experiences on drug treatment by commenting in the box below.