What is the recommended dosing for Belsomra (suvorexant), including initial dose, titration, and adjustments for patients ≥65 years or with moderate hepatic impairment?

Belsomra (Suvorexant) Dosing

Start with 10 mg taken once nightly within 30 minutes of bedtime (with at least 7 hours remaining before planned awakening), and increase to 20 mg if the 10 mg dose is well-tolerated but ineffective; the maximum dose is 20 mg once nightly. 1

Standard Dosing Algorithm

Initial dose: 10 mg once nightly 1

Titration: If 10 mg is well-tolerated but not effective, increase to 20 mg once nightly 1

Maximum dose: 20 mg once nightly 1

Timing: Take within 30 minutes of going to bed, with at least 7 hours remaining before planned awakening 1

Food interaction: Avoid taking with or soon after meals, as food delays absorption and reduces effectiveness 1

Special Population Adjustments

Elderly Patients (≥65 years)

• No dose adjustment required 1
• Use the same 10-20 mg dosing range as younger adults 1
• Clinical trials showed no meaningful differences in safety or effectiveness between elderly and younger patients at recommended doses 1
• Caution: Higher fall risk due to increased drowsiness—counsel patients accordingly 1

Obese Patients and Women

• Start conservatively at 10 mg 1
• Drug exposure is increased in obese patients and women compared to non-obese patients and men 1
• Particularly in obese women: Consider the increased risk of exposure-related adverse effects before increasing to 20 mg 1

Hepatic Impairment

• Mild to moderate: No dose adjustment needed 1
• Severe: Not recommended—suvorexant has not been studied in this population 1

Renal Impairment

• No dose adjustment required regardless of severity 1

Drug Interaction Adjustments

With Moderate CYP3A Inhibitors

• Start at 5 mg once nightly 1
• Generally should not exceed 10 mg 1
• Examples include diltiazem, verapamil, erythromycin, fluconazole

With Strong CYP3A Inhibitors

• Not recommended 1
• Examples include ketoconazole, itraconazole, clarithromycin, ritonavir

With CNS Depressants

• Consider dose reduction of suvorexant and/or the other CNS depressant due to potentially additive effects 1

Clinical Context from Guidelines

The 2017 American Academy of Sleep Medicine guideline provides a weak recommendation for suvorexant as treatment for sleep maintenance insomnia, based on trials using 10,15/20, and 20 mg doses 2. The evidence showed clinically significant reductions in wake after sleep onset at both 10 mg and 20 mg dosages, with the 20 mg dose also showing clinically significant reduction in sleep latency 2. The 2016 American College of Physicians guideline noted that FDA-approved doses are 20 mg for non-elderly patients and 15 mg for elderly patients, though the FDA label now standardizes dosing across age groups 3.

Key Safety Considerations

• Somnolence is the most common adverse effect (13% vs 3% placebo at higher doses) 3, 4
• No evidence of daytime residual effects or withdrawal symptoms at approved doses 2
• Contraindicated in narcolepsy 5
• Not studied in severe obstructive sleep apnea or severe COPD—use with caution in respiratory compromise 1
• Monitor for rare but notable effects: abnormal dreams, sleep paralysis, suicidal ideation (dose-related and typically mild) 5