Last Updated: 2009-03-10 15:59:23 -0400 (Reuters Health)
NEW YORK (Reuters Health) - Patients treated for Parkinson's disease may sometimes develop addictive behaviors, such as pathological gambling, from the excessive use of dopamine agonists, the type of drug primarily used to treat this common neurologic condition, according to a report in the medical journal Neuron.
Dopamine agonists, agents that activate dopamine receptors in the brain, include drugs such as pramipexole, ropinirole, pergolide, bromocriptine, commonly used for Parkinson's disease and restless legs syndrome. These drugs, however, "carry a very definite risk of causing impulse control disorders and addiction," Dr. Alain Dagher from McGill University, Montreal, Quebec, told Reuters Health. "MDs should be aware of these side effects and explicitly warn patients who are started on these drugs."
Dagher and Dr. Trevor W. Robbins from the University of Cambridge, UK, reviewed the associations between dopamine and addictive personality disorders in light current models of learning and addiction.
Risk factors for these disorders in Parkinson's disease patients, the authors explain, include male sex, young age at the time of diagnosis, a history of drug or alcohol abuse, depression, and elevated scores on the personality category of novelty -- all factors that also increase the risk of drug addiction in the general population.
Although it was initially questioned if dopamine agonists actually cause pathological gambling, there is now evidence that dopaminergic therapy generally, and dopamine agonists in particular, are the trigger for pathological gambling and other impulse control disorders in Parkinson's disease.
Chronically low dopamine levels in "patients with untreated Parkinson's disease lead to low novelty-seeking personality and a reduced incidence of addiction," the investigators note. "On the other hand dopaminergic replacement treatment (increases) vulnerability to addiction and impulse control disorders."
"The very clear link between brain dopamine and addiction should convince people that this is a biological disease," Dagher said. "I think this has public policy implications as well as implications for the clinician."
"With respect to Parkinson's patients the answer is simple: discontinue the dopamine agonist in a patient who develops addiction," Dagher concluded. "For the general population, drugs that block dopamine should in theory help treat addiction, but in practice they don't really work, largely due to the fact that side-effects limit the dosing."
SOURCE: Neuron, February 25, 2009.
Dr. Sears comments:
One of the best ways to increase dopamine levels without addictive consequences is the use of high-dose fish oil.