Preventive Effects of Suvorexant on Delirium: A Randomized Placebo-Controlled Trial

OBJECTIVE: No highly effective pharmacologic interventions to prevent delirium have been identified. We examined whether suvorexant, a potent and selective orexin receptor antagonist, is effective for the prevention of delirium. METHODS: We conducted a multicenter, rater-blinded, randomized, placebo-controlled clinical trial in intensive care units and regular acute wards between April 2015 and March 2016. Eligible patients were 65 to 89 years old, newly admitted due to emergency, and able to take medicine orally and had an expected stay or life expectancy of 48 hours or more. Seventy-two patients were randomly assigned using the sealed envelope method to receive suvorexant (15 mg/d; 36 patients) or placebo (36 patients) every night for 3 days. The primary outcome measure was incidence of delirium as determined by the DSM-5. Trained psychiatrists assessed for delirium. RESULTS: We found that delirium developed significantly less often among patients taking suvorexant than among those taking placebo (0% [n/N = 0/36] vs 17% [6/36], respectively, P = .025). Comparison by log-rank test also showed that delirium developed significantly less often among patients taking suvorexant than among those taking placebo (χ² = 6.46, P = .011). Analysis of variance revealed a tendency for main effect of treatment (F = 3.79, P = .053) on the sleep-wake cycle disturbance score (item 1) of the Japanese version of the Delirium Rating Scale-Revised-98 (DRS-R-98-J). There were no significant differences in adverse events. CONCLUSIONS: Suvorexant administered nightly to elderly patients admitted for acute care may provide protection against delirium. Larger studies are needed to show the potential of suvorexant to improve the circadian core domain of delirium. TRIAL REGISTRATION: UMIN Clinical Trials Registry identifier: UMIN000015681​.