The consequences of zopiclone use: Rebound insomnia, development of tolerance, and abuse potential

Rebound phenomena, withdrawal symptoms, development of tolerance, the establishment of drug dependence, and abuse potential are well known with benzodiazepine hypnotics, particularly when these are administered for periods longer than those normally recommended, it is appropriate to determine whether, or to what extent, similar characteristics are associated with the use of zopiclone, a nonbenzodiazepine hypnotic agent. As might be expected for a hypnotic drug with a short elimination half-life of about 5 h, zopiclone use has occasionally been associated with reports of rebound effects. These have, however, almost always been substantially less frequent than those occurring with benzodiazepines. There is no evidence of any marked degree of tolerance occurring to zopiclone. Cross-tolerance may occur with benzodiazepines and there are suggestions that this may help patients who are dependent upon benzodiazepines to withdraw from these drugs, though this aspect of zopiclone use needs further investigation. The development of either physical or psychological dependence on zopiclone following its long-term use, and its abuse by polydrug users, both appear to be rare, in relation to the extent to which zopiclone is used world-wide. There is little evidence of adverse reactions following abrupt withdrawal of zopiclone. It is concluded that, in view of its low dependence and abuse potentials, as well as its extremely low tendency to lead to rebound effects following its withdrawal, zopiclone offers definite advantages over the benzodiazepines.