Comparative tolerability of newer agents for insomnia

Newer treatment options for insomnia include the non-benzodiazepine hypnotics zolpidem, zolpidem-controlled release, zaleplon, zopiclone, eszopiclone and the melatonin receptor agonist, ramelteon. These compounds are generally well tolerated and present favourable safety profiles in comparison with the older benzodiazepines and barbiturates. Commonly cited impairments of memory formation and decrements in psychomotor performance are related to the mechanism of action of hypnotics, and are both dose- and time-dependent. These effects typically are minimal on the morning following night-time administration. The non-benzodiazepines are associated with some risk for dependence and abuse. However, concerns regarding such risks appear to be greater than warranted by empirical evidence. The appropriate therapeutic use of hypnotics is generally not associated with physiological responses that are commonly thought to lead to dependence, such as tolerance or discontinuation effects. Former substance abusers and psychiatric patients appear to be at greatest risk. The labelling of hypnotics was recently updated to incorporate warnings about very rare, but serious adverse events that have been identified in postmarketing surveillance. These events include anaphylaxis (severe allergic reaction); angio-oedema (severe facial swelling); and complex sleep-related behaviours, which may include sleep-driving, making phone calls and preparing and eating food. This article will review the adverse event profiles of these newer sedative hypnotics, their effects on memory and psychomotor performance, abuse liability concerns and the most recent information about the rare adverse effects that prompted the recent revision to the labelling of drugs in the hypnotic class.