Modafinil (brand name Provigil) is a stimulant approved in the US for treatment of shift-work sleep disorder, which shares some characteristics with DSPD. A number of clinicians prescribe it for DSPD patients, as it may improve a sleep-deprived patient's ability to function adequately during socially desirable hours. It is generally not recommended to take modafinil after noon; modafinil is a relatively long-acting drug with a half-life of 15 hours, and taking it during the later part of the day can make it harder to fall asleep at bedtime.