"Sleep attacks" in parkinsonian patients: a side effect of nonergoline dopamine agonists or a class effect of dopamimetic agents?

Recently, sudden "sleep attacks" have been described in parkinsonian patien ts taking the nonergoline dopamine agonists pramipexole and ropinirole. Due to this possible side effect, patients must be instructed not to drive veh icles and to refrain from other activities carrying the risk of self-injury . However, the very existence of sleep attacks remains controversial in sle ep medicine, since a gradual transition from wakefulness to sleep is normal ly observed. Accordingly,sudden onset of sleep, e.g., in narcolepsy or slee p apnea syndrome, is usually associated with excessive daytime sleepiness. Prevalence of sleep disorders and daytime sleepiness have been shown to be increased in Parkinson's disease. Nonergoline dopamine agonists are already known to induce somnolence. Currently, it is not predictable whether sleep attacks represent a sudden transition from wakefulness to sleep or result from an increased propensity to fall asleep, with patients perceiving a sud den onset. Possible pathophysiological mechanisms and legal implications of sleep attacks are discussed.