Suvorexant Side Effects
Suvorexant is generally well-tolerated with somnolence being the primary adverse effect (7% vs 3% placebo), while serious adverse events are rare and not more common than placebo at FDA-approved doses. 1
Common Adverse Effects
The most frequently reported side effects from clinical trials and post-marketing surveillance include:
Most Common (from RCTs)
- Somnolence (daytime sleepiness): 7% with suvorexant vs 3% with placebo - this is the most significant adverse effect 1
- Headache 2, 3
- Dizziness 2, 3
- Fatigue 4, 5
- Abnormal dreams 2, 5
Additional Reported Effects
Post-Marketing Reports
The FDA has documented additional adverse effects reported after market approval 6:
- Palpitations and tachycardia
- Nausea and vomiting
- Psychomotor hyperactivity
- Anxiety
- Pruritus (itching)
Serious Warnings from FDA Labeling
The FDA label carries important warnings about potentially serious neuropsychiatric and behavioral effects 1:
Cognitive and Behavioral Changes
- Amnesia
- Anxiety
- Hallucinations (both hypnagogic/hypnopompic)
- Other neuropsychiatric symptoms
Complex Sleep Behaviors
- Sleep driving and other complex behaviors while not fully awake
- These can occur even at recommended doses
Depression-Related Risks
- Worsening of depression
- Suicidal thinking in individuals with pre-existing depression
REM Sleep-Related Phenomena
- Sleep paralysis
- Cataplexy-like episodes (rare but documented in case reports) 7
Daytime Impairment
- Next-day drowsiness affecting activities requiring alertness
- Increased fall risk, particularly in elderly patients 6
Important Safety Context
Moderate-strength evidence from 3-month trials demonstrates that overall withdrawal rates and withdrawals due to adverse effects do not significantly differ between suvorexant (15-20 mg) and placebo 1. This is a critical distinction from older hypnotics.
Key Clinical Considerations:
FDA medical reviews indicate few serious adverse effects at approved doses (20 mg for non-elderly, 15 mg for elderly), and none were more common than placebo 1. This represents a favorable safety profile compared to benzodiazepines and Z-drugs.
Respiratory Effects
In patients with mild-to-moderate obstructive sleep apnea, suvorexant 40 mg (twice the approved dose) showed a mean increase in Apnea/Hypopnea Index of 2.7, but with wide variability. Clinically meaningful respiratory effects cannot be excluded, and the drug has not been studied in severe OSA 6.
Special Populations at Higher Risk:
- Elderly patients: Higher fall risk due to increased drowsiness 6
- Patients with depression: Monitor for worsening symptoms and suicidal ideation 1
- Patients with psychiatric disorders: In a study of 57 psychiatric patients, 43.9% experienced at least one adverse event, with somnolence (28.8%) and fatigue (11.5%) being most common 4
- Compromised respiratory function: Use with caution; effects in severe OSA unknown 6
Drug Interactions Affecting Side Effects
Avoid combining suvorexant with alcohol - this produces additive psychomotor impairment 6.
Strong CYP3A inhibitors are contraindicated (ketoconazole, clarithromycin, ritonavir, etc.) as they substantially increase suvorexant exposure and risk of adverse effects 6.
With moderate CYP3A inhibitors (diltiazem, erythromycin, fluconazole, grapefruit juice), reduce dose to 5 mg and generally do not exceed 10 mg 6.
Comparative Safety Profile
Unlike benzodiazepines and Z-drugs, suvorexant does not show evidence of significant rebound insomnia or withdrawal symptoms 3. The American Academy of Sleep Medicine guidelines note no evidence of daytime residual effects or withdrawal symptoms in clinical trials 8.
This represents a meaningful safety advantage, as observational studies have linked traditional hypnotics (zolpidem, benzodiazepines) to increased risks of fractures, falls, dementia, and possibly mortality 1.
Monitoring Recommendations
Clinicians should:
- Screen for depression and monitor mood changes, especially suicidal ideation
- Counsel patients about complex sleep behaviors and next-day impairment
- Assess fall risk, particularly in elderly patients
- Avoid prescribing with strong CYP3A inhibitors or alcohol
- Monitor for atypical motor or speech symptoms (rare cataplexy-like phenomena) 7
- In breastfeeding mothers, monitor infants for excessive sedation 6