'Sleep attacks' or 'unintended sleep episodes' occur with dopamine agonists: is this a class effect?

Controversial reports of sudden onset 'sleep attacks' resulting in road traffic accidents have recently been reported in patients with Parkinson's disease (PD) taking the non-ergot dopamine D(2 )/D(3) receptor agonists pramipexole and ropinirole. These reports have generated considerable debate as the concept of 'sleep attacks' is disputed amongst sleep specialists and most believe that isolated 'sleep attacks' not preceded by warning on the background of chronic sleepiness or 'unintended sleepiness' do not exist. A series of case reports suggested that this phenomenon may not be exclusive to the non-ergot dopamine agonists such as pramipexole or ropinirole and indeed may occur with most dopaminergic agents. Recent evidence suggest that a 'sleepiness' or 'hypoactivity' reaction to dopaminergic therapy may be related to underlying dopamine deficiency of PD rather than a drug effect. In this report we provide the evidence for the phenomenon being a class effect attributable to all dopamine agonists currently employed in the management of PD. Controversy surrounding excessive daytime sleepiness (EDS) in PD and the use of the Epworth Sleepiness Scale (ESS) in relation to PD is also discussed. In spite of variable reports, EDS is recognised to be common in PD and is likely to be related to both the disease process and drug therapy. Studies using multiple sleep latency tests have also reported differing results in PD although a recent study indicated that a subset of 'sleepy' patients with PD may experience pathological somnolence with resultant detrimental consequence on daytime and cognitive functions. We recommend that the issue of 'sleepiness' or 'sleep attacks' in PD should be routinely checked in all patients with PD and indirectly assessed by using either the ESS or the recently introduced Parkinson's Disease Sleep Scale. Those with reported 'sleep attacks' or 'unintended sleep episodes' and excessive daytime sleepiness while taking dopamine agonists or dopaminergic agents such as levodopa should have a review of their medication, should not be driving a car on their own and some may merit formal sleep architecture studies. The latter may identify sleep disorders such as secondary narcolepsy which may benefit from the use of a wakefulness promoting agent.