Opposite effects of SSRIs and tandospirone in the treatment of REM sleep behavior disorder.

Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia defined by intermittent loss of electromyographic atonia during REM sleep with emergence of complex and vigorous behaviors. Although the efficacy of several agents for treating RBD has been reported, a rationale for medication has not been established and the exact pathophysiological mechanisms of RBD are uncertain. We encountered a patient with idiopathic RBD that dramatically improved with selective serotonin reuptake inhibitors (SSRIs) and deteriorated with a 5-HT1A partial agonist, tandospirone. We report on the effects of these serotonin-modulating agents, which yield clues to a possible pharmacological approach to RBD.