Parkinson's drugs may cause sudden sleepiness

Drugs called dopamine agonists, used to treat Parkinson's disease, may trigger sudden uncontrollable somnolence in about one in five patients.

The side effect has been reported previously in people with Parkinson's disease being treated with dopamine agonists, including Mirapex and Requip, "but controversy persists concerning their nature, severity, and frequency," according to a report in the Archives of Neurology.

Dr. Jerry Avorn and colleagues from Harvard Medical School, in Boston, quantified the risk of sudden uncontrollable somnolence in 929 patients taking drugs for Parkinson's disease.

The subjects were an average of 66.7 years old and predominantly white and male. They were interviewed about medication use, adverse events, and clinical status in the previous 6 months. The patients' physicians completed record reviews on clinical histories and drug regimens.

Most (91 percent) used levodopa either alone or in combination with another medication. Overall, 39 percent used Mirapex (generic name, pramipexole) alone or in combination with another agent and 18 percent used Requip (ropinirole) alone or in combination with another agent.

Parkinson's disease is a disease of the central nervous system that causes problems with body motions, including tremor (shakiness), rigidity (muscle stiffness), slowed body movements, unstable posture and difficulty walking. It happens when nerve cells (neurons) in a part of the brain called the substantia nigra gradually die. These cells normally produce dopamine, a chemical that helps to relay messages between areas of the brain that control body movement. The death of cells in this area of the brain leads to abnormally low levels of dopamine, which makes it difficult for a person with Parkinson's disease to control muscle tension and muscle movement, both at rest and during periods of activity.

Parkinson's disease affects about 1 million people in the United States, with approximately 50,000 new cases diagnosed each year. It usually occurs in middle age, typically beginning around age 60. However, about 5 percent of patients have early-onset Parkinson's disease and are younger than 40 years old when symptoms begin. Internationally, Parkinson's disease affects about one to two of every 1,000 people. It affects Europeans and North Americans more frequently than Asians or Africans. It is more common in men than in women.
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Twenty-two percent of the respondents reported episodes of uncontrollable somnolence. Of the 206 subjects who reported at least one episode, 34 percent had a small number of events (one to four) and 37 percent reported many frequent events (26 or more). Twelve percent of patients reported daily episodes.