Trade Name(s)

  • Hetlioz

Ther. Class.

Pharm. Class.
melatonin receptor agonists


Treatment of Non-24–Hour Sleep-Wake Disorder (a circadian rhythm disorder more common in totally blind patients).


Acts as an agonist at melatonin MT1  and MT2  receptor sites, which are involved in regulation or circadian rhythm.

Therapeutic Effect(s):

Improved circadian rhythm with improved sleep/wake patterns.


Absorption: 38% absorbed following oral administration, blood levels are ↑ in female patients.

Distribution: Unknown.

Metabolism and Excretion: Extensively metabolized mostly by CYP1A2 and also CYP3A4, metabolited do not contribute significantly to pharmacological effect. Metabolites are primarily excreted in urine, less than 1% as unchanged drug), 4% excreted in feces.

Half-life: 1.3 hr.

TIME/ACTION PROFILE (establishment of circadian rhythm/sleep cycle)



Contraindicated in:

  • Severe hepatic impairment.

Use Cautiously in:

  • Concurrent use of strong CYP1A2 inducers/inhibitors (may alter drug effects)
  • Geri:  ↑ risk of adverse reactions due to ↑ blood levels;
  • OB:  May cause fetal harm, use only if potential benefit justifies potential fetal risk;
  • Lactation: Use cautiously if breastfeeding;
  • Pedi:  Safety and effectiveness not established.

Adverse Reactions/Side Effects

CNS: headache, nightmares/unusual dreams

GI: ↑ liver enzymes

* CAPITALS indicate life-threatening.
Underline indicate most frequent.



  • Concurrent use of  strong CYP1A2 inhibitors  including  fluvoxamine  may ↑ drug effects.
  • Concurrent use of  strong CYP1A2 inducers  including  rifampin  and  cigarette smoke   may ↓ drug effects.
  • Strong CYP3A4 inhibitors, including  ketoconazole  may ↑ blood levels and effects.
  •  Alcohol  may ↑ CNS depression.


PO (Adults): 20 mg at bedtime, taken at the same time every day.


Capsules: 20 mg


  • Assess mental status, sleep patterns, and frequency of daytime naps prior and periodically during therapy.

Lab Test Considerations:

May cause ↑ transaminases.

Potential Diagnoses


  • PO Administer without food before bedtime at the same time each night. Swallow capsule whole; do not open, dissolve, crush, or chew.

Patient/Family Teaching

  • Instruct patient to take tasimelteon as directed at the same time each day. If unable to take at approximately the same time on a given night, skip dose and resume following night. After taking, advise patient to limit activity to preparing to go to bed.
  • Caution patient tasimelteon can impair performance of activities requiring complete mental alertness. Advise patient to avoid driving and other activities requiring alertness after taking tasimelteon.
  • Advise female patient to notify health care professional if pregnancy is planned or suspected or if breastfeeding

Evaluation/Desired Outcomes

Improved circadian rhythm with improved sleep/wake patterns. Due to differences in circadian rhythms, may require daily use for several wks or mo before benefit from tasimelteon is noticeable.

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