November 25, 2015
Recommended Topic Related To:


"The U.S. Food and Drug Administration today approved Hetlioz (tasimelteon), a melatonin receptor agonist, to treat non-24- hour sleep-wake disorder ("non-24") in totally blind individuals. Non-24 is a chronic circadian rhythm (body clock) disorde"...




Included as part of the PRECAUTIONS section.



After taking HETLIOZ, patients should limit their activity to preparing for going to bed. HETLIOZ can potentially impair the performance of activities requiring complete mental alertness.

Nonclinical Toxicology

Carcinogenesis, Mutagenesis, Impairment Of Fertility


Tasimelteon was administered orally for up to two years to mice (30, 100, and 300 mg/kg/day) and rats (20, 100, and 250 mg/kg/day). No evidence of carcinogenic potential was observed in mice; the highest dose tested is approximately 75 times the recommended human dose (RHD) of 20 mg/day, on a mg/m² basis. In rats, the incidence of liver tumors was increased in males (adenoma and carcinoma) and females (adenoma) at 100 and 250 mg/kg/day; the incidence of tumors of the uterus (endometrial adenocarcinoma) and uterus and cervix (squamous cell carcinoma) were increased at 250 mg/kg/day. There was no increase in tumors at the lowest dose tested in rats, which is approximately 10 times the RHD on a mg/m² basis.


Tasimelteon was negative in an in vitro bacterial reverse mutation (Ames) assay, an in vitro cytogenetics assay in primary human lymphocytes, and an in vivo micronucleus assay in rats.

Impairment of Fertility

When male and female rats were given tasimelteon at oral doses of 5, 50, or 500 mg/kg/day prior to and throughout mating and continuing in females to gestation day 7, estrus cycle disruption and decreased fertility were observed at all but the lowest dose tested. The no-effect dose for effects on female reproduction (5 mg/kg/day) is approximately 2 times the RHD on a mg/m² basis.

Use In Specific Populations


Pregnancy Category C

There are no adequate and well-controlled studies of HETLIOZ in pregnant women. In animal studies, administration of tasimelteon during pregnancy resulted in developmental toxicity (embryofetal mortality, neurobehavioral impairment, and decreased growth and development in offspring) at doses greater than those used clinically. HETLIOZ should be used during pregnancy only if the potential benefit justifies the potential risks.

In pregnant rats administered tasimelteon at oral doses of 5, 50, or 500 mg/kg/day during the period of organogenesis, there were no effects on embryofetal development. The highest dose tested is approximately 240 times the recommended human dose (RHD) of 20 mg/day, on a mg/m² basis.

In pregnant rabbits administered tasimelteon at oral doses of 5, 30, or 200 mg/kg/day during the period of organogenesis, embryolethality and embryofetal toxicity (reduced fetal body weight and delayed ossification) were observed at the highest dose tested. The highest dose not associated with adverse effects (30 mg/kg/day) is approximately 30 times the RHD on a mg/m² basis.

Oral administration of tasimelteon (50, 150, or 450 mg/kg/day) to rats throughout organogenesis and lactation resulted in persistent reductions in body weight, delayed sexual maturation and physical development, and neurobehavioral impairment in offspring at the highest dose tested. Reduced body weight in offspring was also observed at the mid-dose. The no effect dose (50 mg/kg/day) is approximately 25 times the RHD on a mg/m² basis.

Nursing Mothers

It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when HETLIOZ is administered to a nursing woman.

Pediatric Use

Safety and effectiveness in pediatric patients have not been established.

Geriatric Use

The risk of adverse reactions may be greater in elderly ( > 65 years) patients than younger patients because exposure to tasimelteon is increased by approximately 2-fold compared with younger patients.

Hepatic Impairment

Dose adjustment is not necessary in patients with mild or moderate hepatic impairment. HETLIOZ has not been studied in patients with severe hepatic impairment (Child-Pugh Class C). Therefore, HETLIOZ is not recommended for use in patients with severe hepatic impairment [see CLINICAL PHARMACOLOGY] .


Smoking causes induction of CYP1A2 levels. The exposure of tasimelteon in smokers was lower than in non-smokers and therefore the efficacy of HETLIOZ may be reduced in smokers [see CLINICAL PHARMACOLOGY] .

This monograph has been modified to include the generic and brand name in many instances.

Last reviewed on RxList: 12/29/2014


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