Before and after its introduction in 1987, zopiclone was the object of investigation in 16 psychometric studies employing both healthy volunteers and insomniac patients. Their common purpose was to determine whether nocturnal doses (usually the standard 7.5 mg) possess residual sedative effects that interfere with skilled safety-relevant performance, such as car driving, over the following day. Most studies have found no residual effects. Those that did, have shown them to be modest in magnitude and not to persist for longer than about 12 hours from the time of dosage. Without altering the general conclusion that zopiclone possesses few if any residual effects of clinical relevance, it must be said that the studies reviewed failed to meet current methodological standards and may have left some important questions unanswered.
