Tasimelteon, sold under the brand name Hetlioz, is a medication approved by the U.S. Food and Drug Administration (FDA) in January 2014, for the treatment of non-24-hour sleep–wake disorder (also called non-24, N24 and N24HSWD). In June 2014, the European Medicines Agency (EMA) accepted an EU filing application for tasimelteon and in July 2015, the drug was approved in the European Union for the treatment of non-24-hour sleep-wake rhythm disorder in totally blind adults, but not in the rarer case of non-24 in sighted people. The most common side effects include headache, somnolence, nausea (feeling sick) and dizziness. Medical uses
In the United States, tasimelteon capsules are indicated for the treatment of non-24-hour sleep–wake disorder (Non-24) in adults and for the treatment of nighttime sleep disturbances in Smith-Magenis Syndrome (SMS) in people sixteen years of age and older. Tasimelteon oral suspension is indicated for the treatment of nighttime sleep disturbances in SMS in children from 3 to 15 years of age.In the European Union, tasimelteon capsules are indicated for the treatment of non-24-hour sleep–wake disorder (Non-24) in totally blind adults.The capsule and liquid suspension forms of tasimelteon are not interchangeable.Tasimelteon is a selective agonist for the melatonin receptors MT1 and MT2, similar to other members of the melatonin receptor agonist class of which ramelteon (2005), melatonin (2007), and agomelatine (2009) were the first approved. As a treatment for N24HSWD, as with melatonin or other melatonin derivatives, the patient may experience improved sleep timing while taking the drug.
In the opinion of Public Citizen, an advocacy group, the FDA erroneously allowed it to be labelled without stating that it is only approved for use by totally blind people. However, FDA updated its press release on Oct. 2, 2014 to clarify the approved use of Hetlioz, which includes both sighted and blind individuals. The update did not change the drug labeling (prescribing information). Toxicity
Experiments with rodents revealed fertility impairments, an increase in certain cancers, and serious adverse events during pregnancy at dosages in excess of what is considered the "human dose". See also
Discovery and development of melatonin receptor agonists

References
External links
"Tasimelteon". Drug Information Portal. U.S. National Library of Medicine.