Tasimelteon (trade name Hetlioz) is a drug approved by the FDA solely for the treatment of non-24-hour sleep?–wake disorder (often designated as N24HSWD) in totally blind adults. It is a selective agonist for the melatonin receptors MT1 and MT2 in the suprachiasmatic nucleus of the brain, similar to other members of the melatonin receptor agonist class of which ramelteon (2005) and agomelatine (2009) were the first approved.

Providing storage is as stated on the product vial and the vial is kept tightly sealed, the product can be stored for up to 24 months.
Wherever possible, you should prepare and use solutions on the same day. However, if you need to make up stock solutions in advance, we recommend that you store the solution as aliquots in tightly sealed vials at -20°C. Generally, these will be useable for up to one month. Before use, and prior to opening the vial we recommend that you allow your product to equilibrate to room temperature for at least 1 hour.