Update on emerging drugs for insomnia.

In recent years, there has been no evidence that the problem of chronic insomnia has faded in the least in US adults; on the contrary, a recent estimate of annual lost productivity due to insomnia was $63.2 billion dollars. However, the proportion of insomniacs who are treated continues to be low, indicating the need for continued development and dissemination of effective therapies. Hypnotic drug development has arguably become more focused in recent years, particularly upon the highly anticipated novel target, the orexin (hypocretin) system. Merck's suvorexant (MK-4305) is the first compound of the so-called dual orexin receptor antagonist (DORA) class expected to be submitted for FDA approval, with a new drug application anticipated in 2012. While there has also been some new activity in the modulation of well-characterized targets with well-characterized agents, such as CNS histamine receptors with low-dose doxepin, a decades-old antidepressant and GABA(A) with sublingual zolpidem, experience with melatonin and serotonin modulators suggests that other targets also exist. Diversifying insomnia drug targets may expand possibilities for customizing hypnotic administration to individualized patient presentation and mechanistic underpinnings. In addition, it may offer improved avenues for combining medications with non-drug treatments such as cognitive behavioral therapy for insomnia (CBT-I).