Researchers pooled safety data for 798 patients with RLS participating in 3 multicenter, double-blind, placebo-controlled trials of pramipexole. The data were analyzed for the occurrence of SOOS.

The trials monitored included a 3-week European trial, a 6-week European trial, and a 12-week US trial, with doses fixed at 0.25, 0.50, or 0.75 mg/day. A total of 575 patients received pramipexole and 223 received placebo.

Lead researcher Arthur S. Walters, MD, director, Center for Sleep Disorders Treatment, Research and Education, New Jersey Neuroscience Institute, JFK Medical Center, Edison, New Jersey, presented the data here on May 3^rd.

Patients with SOOS have episodes of sleep that occurs without the forewarning effect of drowsiness.

Patients were asked to report SOOS during all evaluations, and to fill out the Epworth Sleepiness Scale (ESS) to assess daytime sleepiness.

Results show that episodes of SOS were rare, with equivalently low rates for pramipexole (0.3%) and placebo (0.9%).

SOOS occurred 4 times during the US trial alone: in 2 placebo-group patients, twice in 1 patient in the 0.25-mg pramipexole group, and in 1 patient in the 0.50-mg pramipexole group. None of these SOOS events met the criteria for a serious adverse event. Three of the 4 patients reporting SOOS exhibited an end-of-treatment ESS score over 16, which is indicative of excessive daytime sleepiness.

Whether pramipexole causes SOOS in patients receiving it as therapy for Parkinson's disease has been the subject of much controversy in the recent medical literature, according to the researchers. Some authors purport that the entire dopamine agonist class can cause SOOS, while others argue that there are inherent difficulties in defining a target population at risk of SOOS.

Any number of reasons for sleep disturbance may exist in various individuals irrespective of medication use, noted Dr. Walters, including nighttime wakefulness, insomnia, alcohol use, sleep apnea, and more.

RLS patients taking pramipexole, he added, are generally not taking the drug until the evening, and no recommendation has been made against driving. These patients, however, should be monitored carefully for sleep disturbance so that individual recommendations can be made, Dr. Walters concluded.

Pramipexole is marketed as Mirapex by Boehringer Ingelheim Pharma GmbH & Co., KG, Ingelheim, Germany.


[Presentation title: Monitoring for Sudden Onset of Sleep in Placebo-Controlled Trials of Pramipexole for Restless Legs Syndrome. Abstract P06.003]

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