Armodafinil is the (R)-enantiomer of the wakepromoting compound modafinil (racemic), with a considerably longer half-life of 10-15 hours. Armodafinil (developed by Cephalon, Frazer, PA, USA) was approved in June 2007 for the treatment of excessive sleepiness associated with narcolepsy, obstructive sleep apnea syndrome and shift work disorder, and the indications are the same as those for modafinil. Like modafinil, the mechanisms of action of armodafinil are not fully characterized and are under debate. Clinical trials in these sleep disorders demonstrated an enhanced efficacy for wake promotion (wake sustained for a longer time period using doses lower than those of modafinil). The safety profile is consistent with that of modafinil, and armodafinil is well tolerated by the patients. Like modafinil, armodafinil is classified as a non-narcotic Schedule IV compound. Many patients with excessive sleepiness may prefer the longer duration of effect and may have better compliance (with low doses) with armodafinil. The commercial challenge to armodafinil may come from generic modafinil, which may become available in 2012, as well as from classical amphetamine and amphetamine-like compounds (for the treatment of narcolepsy).