Parasomnia Induced by Lemborexant: a Case Report.

Lemborexant, an orexin receptor antagonist, is effective not only for sleep disorders but also for preventing and treating delirium. To date, no complex sleep-related behaviors due to lemborexant have been reported. Herein, we present the case of a 69-year-old male patient who was hospitalized for oral floor and tongue cancer and developed delirium after surgery; however, upon lemborexant dosage increase, used to treat insomnia, he developed abnormal nocturnal behavior. This symptom rapidly improved when lemborexant was discontinued. Distinguishing parasomnia from delirium is important because the treatment of these two conditions differs. Although rapid eye movement sleep behavior or sleepwalking was the cause of this parasomnia, a definitive diagnosis could not be established. If qualitatively distinct abnormal behavior is observed compared to delirium after increasing lemborexant dosage, the possibility of parasomnia should be considered.