Popular Parkinson Disease Medications Can Induce Uncontrollable Sleepiness

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Uncontrollable sleepiness

An estimated 1.5 million Americans have Parkinson disease (PD), a brain disorder that impairs the body's ability to produce dopamine, which is essential to controlling movements. While several classes of medications are available to control symptoms, many patients with PD often experience somnolence or uncontrollable sleepiness. Scientists are unclear if this phenomenon is caused by the disease or by the medications used for treatment. In an effort to better understand this problem, researchers from Brigham and Women's Hospital (BWH) examined a popular class of medications used to treat the disease - dopamine agonists (DA) - and found that patients taking these drugs had a three-fold increased risk of experiencing the sudden onset of uncontrollable sleepiness compared to patients on other medications. This side effect has dangerous implications particularly among PD patients who are driving. Details of this research will be published in the August 2005 issue of the Archives of Neurology.

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According to the study's lead author, BWH and Harvard Medical School (HMS) researcher Jerry Avorn, MD, this risk factor should be considered when prescribing PD patients DA therapy. "Prescribing medication is always a risk versus benefit analysis for each patient. For those who suffer from Parkinson disease, we now have strong evidence that dopamine agonists can produce extreme sudden-onset sleepiness. With this information, clinicians need to evaluate this side effect versus the benefits many patients derive from these drugs. And, scientists developing new therapies need to consider how to control this potentially hazardous side effect."

In the largest published study of the increased risk of uncontrollable sleepiness with DA therapy, Avorn and colleagues analyzed data culled from extensive interviews they conducted with 929 patients diagnosed with PD. Patients were an average of 66 years old, and most were white and male. Patients were asked about incidents of uncontrollably falling asleep during social activity or while driving. The researchers found that a surprisingly large number - 206 respondents, or 22 percent - reported at least one episode of irresistible and inappropriate somnolence during the 180 days preceding the interview. After controlling for confounding factors such as age, sex, PD duration and severity, frailty and other medication use, they determined that patients receiving a dopamine agonist - including agents such as pramipexole (Mirapex), ropinirole (Reqip) or pergolide (Permax) - were nearly three times as likely to have such episodes as patients taking other PD medications.

"Greater attention to this potentially serious adverse effect will be necessary to improve the safety of use of this important category of PD drugs. In the interim, physicians should specifically ask about this under-appreciated problem and consider a different class of drugs such as levodopa or anticholinergic agents for such patients," said Avorn.

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