Brain Implant for Parkinson’s Disease Linked to Impulsive Behavior

Parkinson’s Disease, a degenerative disorder of the central nervous system that often impairs the sufferer’s motor skills and speech, affects at least one million Americans. Sufferers have increasingly severe tremors and periodically stiff or frozen limbs as brain cells stop producing a chemical crucial for movement called dopamine.

First lines of treatment include medications to stimulate dopamine. However, recent studies found that certain medications used to treat symptoms of Parkinson’s, such as Mirapex, are linked to compulsive behaviors such as excessive gambling, sex, shopping, or eating.

When medications fail, deep brain stimulation (DBS) surgery is required to control tremors. DBS surgery involves placing electrodes into a small region of the brain to control movement. Research published on October 25, 2007 found a correlation between DBS brain implants and a completely different kind of impulsiveness. The brain implant can leave patients unable to learn from bad experiences, such as losing a poker hand.

The study involved an analysis of the experiences of 15 Parkinson’s patients taking dopamine drugs, 17 Parkinson’s patients who received DBS surgery, and 14 healthy older adults playing specialized computer games to probe decision-making.

In the study, patients were shown Japanese characters and were asked to pick the “correct” answer. The computer would then supply a response of “correct” or “incorrect.” Patients’ brains would learn to prefer some characters over others even though none of the patients knew Japanese.

The research team paired “correct” symbols to stimulate a “win-win” decision and “incorrect” symbols to simulate “lesser of two evils” and “right-wrong” decisions.

The study found that healthy older adults and Parkinson’s patients on dopamine drugs hesitated briefly when faced with win-win or lose-lose decisions. Researchers concluded these patients hesitated to allow time to weigh options and consequences.

Parkinson’s patients who received DBS surgery did not hesitate with lose-lose choices and actually sped up win-win decisions. This result supported previous research that dopamine drugs can hinder learning from negative feedback. When Parkinson’s patients with DBS surgery had their brain implant switched off, they stopped rushing close call decisions.

Source: Lauran Neergaard, “Parkinson’s Tie to Impulsiveness Studied,” Associated Press, October 25, 2007.

Some say Requip could be over-prescribed for relief from restless legs syndrome

Drug linked to sudden narcolepsy and compulsive behaviors

The Restless Legs Syndrome Foundation of Rochester, MN believes GlaxoSmithKline’s ads last year for its new drug Requip have raised public awareness of an under-diagnosed condition; but some others say the ads may have misled people into believing they needed medication for a disease they did not have. Glaxo’s advertisement, featuring the words “It’s frustrating” in the shape of restlessly moving legs, was at the heart of a $27 million advertising spend which pushed Requip’s U.S. sales to $146 million in 2005. Critics of pharmaceutical advertising say Glaxo causes people who may just have a hard time sitting still to think they have a dangerous condition. That may lead these persons to take a drug that may be more risky than they think.

Restless legs syndrome causes sufferers to jerk involuntarily while sleeping. The symptoms are sometimes so intense they severely limit victims’ lives and sleep deprivation symptoms leave them disabled. Victims experience an overwhelming urge to move their legs, sometimes described as a vague tugging, itching or “creepy-crawly” sensation in the legs. The neurological condition appears to be hereditary, and its cause is unknown.

Requip is a dopamine booster that is also prescribed for Parkinson’s disease. The drug is increasingly being linked to side effects such as sudden narcolepsy, where victims will fall asleep without warning, and compulsive or addictive behavior, such as gambling, and compulsive shopping. Requip and Mirapex, a similar dopamine drug, are part of a class of drugs being closely studied by drug researchers for their link to these compulsive behaviors. Researchers say that dopamine serves as a chemical “pleasure stimulator” that when continually turned on reinforces addictive habits like drug-taking, gambling and obsessively playing video games without stopping.

Sources: Rob Stein, “Ad has some asking: Are we all turning into patients?,” Washington Post, June 25, 2006, accessed June 27, 2006; Denise Gellene, “Tremor drug linked to odd compulsions,” Baltimore Sun, June 4, 2006, accessed June 27, 2006.

Mirapex linked to compulsive behavior

Mayo Clinic study: Mirapex can induce compulsive behavior in rare cases

Researchers at the Mayo Clinic in Rochester, NY, have found a link between drugs used to treat symptoms of Parkinson’s disease and compulsive gambling, eating, drinking and sexual activity in patients with the disease. In a study published online Monday by the Archives of Neurology, researchers said that between 2002 and 2004 they identified 11 Parkinson’s patients at the clinic who reported sudden, inexplicable changes in personality and behavior after starting drug therapy. Since then they have identified an additional 14 patients who were not included in the original study.

Most often the behavior started within months of taking the drug Mirapex, the most commonly prescribed drug for Parkinson’s. Other drugs linked to the behavior include Requip and Permax. Parkinson’s in a slow, degenerative nervous system disorder caused when people do not make enough dopamine, a messenger chemical that carries information through the area of the brain that controls movement.

Many Parkinson’s drugs are dopamine agonists, compounds that mimic the behavior of dopamine in the brain in order to control symptoms. Dopamine plays a key role in the pleasure and reward area of the brain. When it goes awry, people can develop serious addictions.

Compulsive behavior has been seen to stop once the drug is discontinued for a length of time. In one case, a 52-year old man began gambling daily, gained 50 pounds from compulsive eating, and engaged in numerous extramarital affairs. Paul Sanberg, distinguished professor of neurosurgery and director of the University of South Florida Center for Aging and Brain repair, said that the fact that patients were able to reduce the behavior by stopping drug therapy “implies that it was the drug” that caused the compulsive behavior.

Mirapex is manufactured by Boehringer-Ingelheim Pharmaceuticals, Inc., and was approved for sale in the U.S. in 1997. A class-action suit was filed against the company last year because of its link to compulsive behavior in patients. The company insists there is no scientific evidence that Mirapex causes compulsive behavior, but it has revised patient insert literature to include compulsive behavior among the drug’s potential side effects.

Sources: Josephine Marcotty, “Parkinson’s drugs linked to gambling, other compulsions,” Star Tribune, July 12, 2005; “Parkinson’s Treatment Linked to Compulsive Gambling,” ScientificAmerican.com, July 12, 2005; Amanda Gardner, “Some Parkinson’s Drugs May Trigger Compulsive Gambling,” HealthDay, July 11, 2005.