Zopiclone
Zopiclone was developed and first introduced in 1986 by Rhône-Poulenc S.A., now part of Sanofi-Aventis, the main worldwide manufacturer. Initially, it was promoted as an improvement on benzodiazepines, but a recent meta-analysis found it was no better than benzodiazepines in any of the aspects assessed. On April 4, 2005, the U.S. Drug Enforcement Administration listed zopiclone under schedule IV, due to evidence that the drug has addictive properties similar to benzodiazepines.
Azapirone
Azapirones are poorly but nonetheless appreciably absorbed and have a rapid onset of action, but have only very short half-lives ranging from 1–3 hours. As a result, they must be administered 2-3 times a day. The only exception to this rule is umespirone, which has a very long duration with a single dose lasting as long as 23 hours. Unfortunately, umespirone has not been commercialized. Although never commercially produced, Bristol-Myers Squibb applied for a patent on Oct 28, 1993 and received the patent on Jul 11, 1995 for an extended release formulation of buspirone. An extended release formulation of gepirone is currently under development and if approved, should help to improve this issue.