There is an increased risk of somnolence, daytime sleepiness, impaired reaction time and impaired driving skills.
Concerns have also been raised regarding unconscious nighttime activity, sleep paralysis, hypnagogic hallucinations, mild cataplexy, and suicidal ideation with suvorexant use.[1]
These adverse effects have a dose-dependent relationship; patients treated with up to four times the maximum recommended dose experienced somnolence twice as frequently as those treated with the recommended dose (10 mg and 20 mg). In fact, the Food and Drug Administration (FDA) initially rejected high doses of suvorexant 30 mg and 40 mg proposed by the manufacturer (Merck), because it posed a dangerous risk of next-day drowsiness that could lead to driving accidents. The FDA eventually approved lower doses of the drug (5 mg, 10 mg, and 20 mg) to mitigate this side effect.