Hetlioz (Tasimelteon)

Hetlioz is indicated for the treatment of non‑24‑hour sleep‑wake disorder, a circadian rhythm condition that commonly affects individuals who are totally blind.

• Improves alignment of the sleep‑wake cycle with the 24‑hour day in blind patients lacking light perception.
• Reduces the frequency of nighttime awakenings and daytime sleepiness associated with non‑24‑hour disorder.
• Supports more consistent sleep onset and maintenance, facilitating daily functioning.
• May be considered when behavioral strategies for circadian entrainment have been insufficient.

• Tasimelteon acts as a selective agonist of the melatonin MT1 and MT2 receptors located in the suprachiasmatic nucleus of the hypothalamus. By binding to these receptors, it mimics the action of endogenous melatonin, promoting phase‑shifting and entrainment of the central circadian clock to the external 24‑hour light‑dark cycle, thereby helping to normalize sleep‑wake timing in individuals with disrupted circadian rhythms.

The safety profile of Hetlioz includes a range of observed adverse reactions, which are categorized by frequency and severity.

Common

• Headache, which may be mild to moderate in intensity and often transient.
• Nausea or an upset stomach, typically occurring shortly after ingestion.
• Dizziness or a light‑headed sensation, especially when standing quickly.
• Fatigue or mild somnolence, which can affect daytime alertness.
• Dry mouth, which may cause discomfort but is usually reversible.
• Insomnia or difficulty staying asleep, reported by a minority of patients.

Serious

• Severe allergic reaction, presenting as rash, itching, swelling of the face or throat, or difficulty breathing.
• Significant changes in mood or behavior, including new or worsening depression, anxiety, or suicidal thoughts.

Before initiating Hetlioz, certain precautionary considerations should be reviewed to ensure safe use.

• Assess for known hypersensitivity to tasimelteon or any excipients in the formulation.
• Use caution in patients with hepatic impairment, as metabolism may be altered.
• Evaluate renal function, especially in individuals with severe kidney disease.
• Consider potential effects on driving or operating machinery due to possible dizziness or somnolence.
• Discuss pregnancy and lactation status, as safety data are limited.
• Monitor for mood changes, particularly in patients with a history of depression or suicidal ideation.
• Avoid abrupt discontinuation without medical guidance, as circadian rhythm disturbances may recur.

Hetlioz may interact with other medicines, and awareness of these potential interactions helps to minimize adverse outcomes.

Avoid

• Strong CYP1A2 inhibitors (e.g., fluvoxamine) that can markedly increase tasimelteon plasma concentrations.
• Concomitant use with other melatonin receptor agonists, which may amplify pharmacologic effects.

Use with caution

• CYP1A2 inducers (e.g., smoking, rifampin) that could reduce tasimelteon exposure.
• CNS depressants such as benzodiazepines or antihistamines, which may enhance sedation.
• Drugs that affect hepatic metabolism, including certain antifungals and antivirals, requiring dose consideration.
• Herbal supplements such as St. John’s wort, a CYP1A2 inducer, which may lower tasimelteon effectiveness.