tasimelteon

General Information

Tasimelteon is a melatonin receptor agonist indicated for treatment of Non-24-Hour Sleep-Wake Disorder (Non-24) in adults (label).

Non-24 is a circadian rhythm disorder. Clinical framing emphasizes circadian entrainment and consistency rather than immediate hypnotic sedation; drug effects may take weeks or months to emerge (label/clinical).

In pivotal phase 3 trials in totally blind adults with Non-24, tasimelteon increased circadian entrainment and improved clinical sleep measures versus placebo; ongoing nightly dosing was needed to sustain benefit (trial/clinical).

Tasimelteon is not a controlled substance and generally has low misuse potential, but next-day somnolence can occur and interaction management is clinically important (label/clinical).

Strong CYP1A2 inhibitors (e.g., fluvoxamine) and strong CYP3A4 inducers (e.g., rifampin) are avoided due to large exposure changes; smoking may reduce exposure via CYP1A2 induction (label).

The tasimelteon compare view, evidence feed, and print page support review of melatonin-pathway agents and alternative sleep strategies.

Tasimelteon is a niche but clinically important option for Non-24; real-world success depends on adherence to consistent timing, patience for delayed onset of circadian effects, and careful interaction management (label/clinical).

Mechanism of Action

Refer to the Glossary entry on Neurotransmitters for background on receptor systems involved in serious mental illness.

Dual melatonin receptor agonist (MT1/MT2). Clinical framing emphasizes shifting/entraining circadian timing rather than producing rapid sedative-hypnotic effects (label/clinical).

Because benefit can take weeks to months, follow-up often focuses on sleep timing and daytime function rather than short-term sleep latency alone (clinical).

• Melatonin receptor agonism (MT1/MT2).

Metabolism and Pharmacokinetics

• Tasimelteon is extensively metabolized. CYP1A2 and CYP3A4 are the major isozymes involved in metabolism (label).
• Observed mean elimination half-life is ~1.3 hours; metabolite half-lives are longer (label).
• Food affects absorption; label guidance emphasizes administration without food and consistent nightly timing (label).

Dosing and Administration

• Adults: 20 mg taken 1 hour before bedtime, at the same time every night; administer without food (label).
• If a dose is missed or cannot be taken at the usual time, the dose is skipped and the next dose is taken as scheduled (label).
• Tasimelteon capsules and tasimelteon oral suspension are not substitutable; formulation changes require attention to non-interchangeability guidance (label).
• Because circadian effects may take weeks or months, follow-up intervals commonly account for delayed onset before concluding lack of efficacy (clinical).

Monitoring & Labs

• 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).

Adverse Effects

Interactions

• Avoid strong CYP1A2 inhibitors (e.g., fluvoxamine) due to increased exposure (label).
• Avoid strong CYP3A4 inducers (e.g., rifampin) due to decreased exposure (label).
• Smoking induces CYP1A2 and lowers exposure; reduced efficacy is a plausible clinical issue in smokers (label/clinical).

Other Useful Information

• AASM guidelines for circadian rhythm sleep-wake disorders emphasize diagnosis confirmation and circadian tracking. Combining medication with structured routines and monitoring can clarify entrainment-based response (AASM/clinical).
• Adjunctive circadian strategies (consistent sleep opportunity, stable timing of meals/activity, and morning bright light exposure in sighted patients when appropriate) often determine real-world success; sleep logs and actigraphy can help document entrainment and guide reassessment (clinical).
• In serious mental illness, circadian stabilization may support mood stability and function, but monitoring for daytime sedation and interaction burden remains important in polypharmacy (clinical).

References

1. Tasimelteon capsules prescribing information — DailyMed (2025)
2. 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)
3. 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)
4. Tasimelteon: A Review IN NON 24 Hour Sleep Wake Disorder IN Totally Blind Individuals — CNS Drugs (2016)