Avorn J et al. (2005) Sudden uncontrollable somnolence and medication use in Parkinson disease. Arch Neurol 62: 1242–1248

Recent studies have suggested that dopamine agonists (DAs), widely used in Parkinson's disease (PD) management, might increase the risk of sudden uncontrollable somnolence. Avorn et al. investigated the nature and frequency of such episodes, and explored possible links to medication use.

Of 1,041 recruited PD patients, 929 completed a 45–60 min telephone interview with researchers, who questioned medication use, adverse events, general sleepiness and clinical status during the 6-month period before interview. The primary endpoint was an episode of “uncontrollably falling asleep” (e.g. while driving or talking to friends).

At least one episode of uncontrollable somnolence was reported by 206 patients (22%), 24 of whom (12%) had daily episodes. Multivariate regression analyses (adjusted for various patient characteristics) showed that the use of any DA (pramipexole, ropinirole, pergolide or bromocriptine) increased the risk of uncontrollable somnolence almost three-fold compared with any other antiparkinsonian medication. DAs increased this risk even when a patient's level of overall sleepiness was taken into account. Compared with levodopa alone, individual DAs showed a dose-dependent, increased risk of uncontrollable somnolence. Furthermore, men were more than twice as likely as women to experience uncontrollable somnolence, regardless of medication.

Avorn et al. conclude that, although DAs have a number of advantages compared with other PD treatments, the finding that they can cause sudden uncontrollable somnolence in a dose-related manner must be taken into consideration when selecting a therapy and dosage for a particular PD patient.