tasimelteon

General information

• Class: Adjunctive therapy
• Common US brands: Hetlioz, Hetlioz LQ
• Typical dose range: Adults: 20 mg taken 1 hour before bedtime, at the same time every night; administer without food (label).
• Therapeutic drug monitoring not routinely recommended.
• Last reviewed: 2025-12-30

Dosing & forms

• Forms/strengths: Capsules: 20 mg (label).
• Frequency: Adults: 20 mg taken 1 hour before bedtime, at the same time every night; administer without food (label).
• Food: Take on an empty stomach.
• Typical range: Adults: 20 mg taken 1 hour before bedtime, at the same time every night; administer without food (label).

Mechanism (brief)

Melatonin receptor agonist (tasimelteon; MT1/MT2) indicated for treatment of Non-24-Hour Sleep-Wake Disorder (Non-24) in adults; requires consistent nightly dosing and may take weeks to months for effect, with clinically important CYP1A2/CYP3A4 interaction considerations.

Metabolism & Half‑life

• Metabolism: CYP1A2, CYP3A4
• Half‑life: Single-dose mean 1.3 h

Therapeutic Drug Monitoring (TDM)

Recommended: No

Monitoring highlights

• Next-day somnolence monitoring and fall risk assessment (label/clinical).
• Drug interaction review (CYP1A2 inhibitors; CYP3A4 inducers; smoking) (label/clinical).
• Consistency tracking (dose timing and sleep timing) to interpret response (clinical).
• Reassessment interval planning given delayed onset of circadian effects (clinical).
• Circadian tracking (sleep-wake diary; actigraphy when available) and evaluation for comorbid sleep disorders when response is unclear (clinical).

Sources

• Tasimelteon capsules prescribing information — DailyMed (2025)
• Clinical Practice Guideline for the Treatment of Intrinsic Circadian Rhythm Sleep-Wake Disorders: Advanced Sleep-Wake Phase Disorder (ASWPD), Delayed Sleep-Wake Phase Disorder (DSWPD), Non-24-Hour Sleep-Wake Rhythm Disorder (N24SWD), and Irregular Sleep-Wake Rhythm Disorder (ISWRD). An Update for 2015 — Journal of Clinical Sleep Medicine (2015)
• Tasimelteon for non-24-hour sleep-wake disorder in totally blind people (SET and RESET): two multicentre, randomised, double-masked, placebo-controlled phase 3 trials — The Lancet (2015)
• Tasimelteon: A Review in Non-24-Hour Sleep-Wake Disorder in Totally Blind Individuals — CNS Drugs (2016)