What is the recommended dosing of suvorexant (including starting dose, titration schedule, maximum dose, and adjustments for patients ≥65 years old or with moderate hepatic impairment)?

Suvorexant Dosing Recommendations

Start with 10 mg taken no more than once per night within 30 minutes of going to bed, with at least 7 hours remaining before planned awakening; if tolerated but insufficiently effective, increase to a maximum of 20 mg nightly. 1, 2

Standard Adult Dosing (Ages 18-64)

• Starting dose: 10 mg once nightly 1
• Titration: May increase to 20 mg if the 10 mg dose is well-tolerated but provides insufficient efficacy 1, 2
• Maximum dose: 20 mg once nightly 3, 4
• Timing: Take within 30 minutes of bedtime with at least 7 hours remaining before planned awakening 1

The FDA specifically rejected higher doses (30-40 mg) due to excessive daytime somnolence (up to 8.4% versus 3.1% with placebo at the approved 15/20 mg doses), despite superior efficacy at these higher doses. 3, 4

Elderly Patients (≥65 Years)

• Starting dose: 10 mg once nightly 5
• Maximum dose: 20 mg once nightly 5
• No dose adjustment required based on age alone 1

The American Geriatrics Society confirms that no specific dose reduction is needed for advanced age, though the 15 mg dose studied in elderly populations showed good efficacy with improved safety compared to 30 mg. 6, 5 Clinical trials in elderly patients demonstrated that suvorexant 15-30 mg was effective and well-tolerated over 3 months, with discontinuation rates due to adverse events of only 3.5% (15 mg) and 6.4% (30 mg) versus 5.5% for placebo. 5

Hepatic Impairment

• Mild-to-moderate hepatic impairment: No dose adjustment needed 1
• Severe hepatic impairment: Not recommended (suvorexant is metabolized by hepatic CYP3A) 1

Renal Impairment

• No dose adjustment required for any degree of renal impairment 1

Special Populations Requiring Conservative Dosing

Women and obese patients have higher drug concentrations, so obese women should receive particularly conservative dosing (start at 10 mg and increase cautiously). 1

Drug levels are elevated in women and obese individuals due to pharmacokinetic differences; therefore, the lowest effective dose should be prioritized in these populations. 1

Critical Administration Instructions

• Do NOT take with food: Food delays absorption and reduces efficacy 1
• Ensure adequate sleep opportunity: At least 7 hours must remain before planned awakening to minimize next-day impairment 1
• Avoid strong CYP3A inhibitors: Suvorexant should be avoided in combination with strong CYP3A inhibitors due to significantly increased drug levels 1

Important Drug Interactions

Monitor for additive effects when combining with:

• SSRIs and other serotonergic agents (potential for mild serotonergic syndrome) 6
• Benzodiazepines, antidepressants, and antipsychotics (potential interactions) 2

Contraindications

• Narcolepsy: Suvorexant is contraindicated 1
• Children: Not studied in pediatric populations 1

Common Pitfalls to Avoid

• Avoid starting at 20 mg: The 10 mg dose provides meaningful benefit with better tolerability; reserve 20 mg for patients who tolerate but do not respond adequately to 10 mg 4, 2
• Do not exceed 20 mg: Higher doses cause dose-dependent somnolence without proportional efficacy gains 3, 4
• Warn patients about next-day impairment: Somnolence occurs in approximately 7% of patients at 20 mg versus 3% with placebo, and patients should be advised about potential driving impairment 3

Expected Efficacy at Approved Doses

At 20 mg, suvorexant reduces sleep latency by approximately 22 minutes and increases total sleep time by about 50 minutes on objective polysomnography, though subjective improvements are more modest (5.5-10.6 minutes). 3, 4 The 10 mg dose shows smaller but clinically meaningful benefits with improved safety. 4