Tasimelteon

HETLIOZ

Open Tasimelteon in the interactive console ↗

Pronunciation: tas-i-MEL-tee-on

Tasimelteon ballicule: receptor binding, kinetics and half-life diagram — Mechanism of action: Tasimelteon ballicule

Tasimelteon HETLIOZ mascot mnemonic cartoon — Visual mnemonic: Tasimelteon mascot
**“Tassel melty on Heater”**
for non-24-hour sleep-wake disorder

What it isMT1 and MT2 melatonin receptor agonist; non-24-hour sleep-wake disorder in blind patients.

Why this oneIt entrains the circadian clock in people with no light perception, which nothing else does.

What limits itEntrainment takes weeks to months. CYP1A2 and CYP3A4 dependent; avoid with fluvoxamine.

Tasimelteon molecular structure (skeletal formula) — Molecular structure: Tasimelteon

Tasimelteon prescription history

Animated chart of estimated U.S. prescriptions per year, Sleep meds (1869–2026). Tasimelteon enters in 2014 (estimated).

FDA-approved for

non-24-hour sleep-wake disorder (2014)

Principal riskEntrainment takes weeks to months

Classes and tags

Clinical profile

Therapeutic safety burden1 / 4

Overdose danger1 / 4

Weight-gain liability0 / 4

Sedation liability3 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk2 / 4

Legacy pregnancy categoryC

Defining liabilitySomnolence, headache and hepatic enzyme elevations; acute toxicity is generally limited.

FDA label

Read the full label on DailyMed ↗

NO BOXED WARNINGS

FDA dosing	Population	Start	Target	Max
Non-24-hour sleep-wake disorder	Adults (capsules)	20 mg QHS	20 mg QHS	20 mg QHS
Nighttime sleep disturbances in Smith-Magenis syndrome	≥16 yr (capsules)	20 mg QHS	20 mg QHS	20 mg QHS
Nighttime sleep disturbances in Smith-Magenis syndrome, ≤28 kg	Pediatric 3-15 yr (oral suspension)	0.7 mg/kg QHS	0.7 mg/kg QHS	0.7 mg/kg QHS
Nighttime sleep disturbances in Smith-Magenis syndrome, >28 kg	Pediatric 3-15 yr (oral suspension)	20 mg QHS	20 mg QHS	20 mg QHS

Renal Undefined

Hepatic Severe: not studied, not recommended

Instructions

Take one hour before bedtime, at the same time every night
Take without food
Capsules and LQ oral suspension are not substitutable
If unable to take at about the same time, skip that dose and take next as scheduled
Non-24: drug effect may take weeks to months

Available strengths

cap 20 mg
susp 4 mg/mL

Cautions

Somnolence — after dosing, limit activity to preparing for bed; impairs mental-alertness tasks

Adverse reactions

Headache
Increased ALT
Nightmares/unusual dreams
Upper respiratory tract infection
Urinary tract infection

Pregnancy Insufficient human data; no embryofetal toxicity in rats at tested exposures

Lactation No human or animal milk data

Cost

Tasimelteon (HETLIOZ)

What pharmacies pay · NADAC 9/30/26

Strength		#/mo	generic $	CostPlus
20 mg	cap	30 qd	$6,847.44/mo	offered
4 mg/mL	susp	per unit		not offered

Generic entry2022

Open Tasimelteon in the interactive console ↗

Memory aids: interaction avatars

CYP1A2 substrate

Open Tasimelteon in the interactive console ↗

Self-check

What does tasimelteon entrain in people without light perception?
The circadian clock.
How long can tasimelteon entrainment take?
Weeks to months.