A new study has shown that dopamine receptor agonist drugs are linked with higher risks for hypersexuality, compulsive shopping and pathological gambling.
According to the lead author of the study, Thomas J Moore from the Institute for Safe Medication Practices in Alexandria, Virginia, and his colleagues, cases of these severe impulse control disorders have been linked to the drugs for more than a decade, and their findings indicate that the abnormal behaviour is terminated when patients stop taking the drugs.
The Parkinson’s Disease Foundation’s website states that an earlier study indicated that dopamine agonists are linked to compulsive behaviours in around 14% of patients.
In a bid to investigate the link further, Moore’s team undertook analysis of 2.7m serious drug side effects which had been reported in the FDA Adverse Event Reporting System between 2003 and 2012 within the US and 21 other countries. They identified around 1580 impulse control disorder events of which 710 were linked to dopamine agonist drugs and 870 to other drugs.
The dopamine agonists had most often been prescribed for the treatment of Parkinson’s disease, but there were also cases where it was prescribed for restless leg syndrome.
Moore stated that dopamine agonist drugs were 277 times more likely to end in a report of specific impulse control symptoms than many other drugs. He said this indicates that reports which link a drug to hypersexuality and pathological gambling were extremely rare, other than in this group of drugs.
According to Joshua J Gagne of Brigham and Women’s Hospital and Harvard Medical School, this indicates a large risk increase. He said the actual risk may be higher as the data is dependent on official reports linked to the side effects of drugs.
The new results were accompanied by an editorial written by Gagne, which appeared in JAMA Internal Medicine online on October 20.
A link has been established between impulse control disorders and antipsychotics or antidepressants, however it was not as powerful as the link with drugs for Parkinson’s.
Dopamine agonist drugs, including ropinirole, bromocriptine (Cycloset), apomorphine (Apokyn), pramipexole, (Mirapex), cabergoline, and rotigotine n the US, activate dopamine receptors even if dopamine itself is absent. None of these six drugs come with what is called Boxed Warnings about the possible behavioural side effects, although they should all have prominent and clear warnings, according to the authors.
Gagne said dopamine plays an important role in the regulation of behaviour and drugs which affect the method in which the brain uses dopamine could reduce the limit for impulsive behaviours. He said that as they learn more and more about what it actually does, it makes biological sense that it is causal.
He said that these interesting results may be the best evidence they can get that is linked to the behavioural consequences of this type of drug. He added that it is very difficult to study as many patients may be loathe to disclose their sexual behaviour or gambling problems.
Gagne stated that this serves as an additional piece of the puzzle that something is happening with these drugs. He said doctors should understand and consider the risks to the benefits. He added that there is a massive difference between a patient suffering with advanced Parkinson’s disease who has severely impaired motor control, and a patient who is suffering with a mild case of restless leg syndrome.
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