Zopiclone

Zopiclone is a sedative-hypnotic drug belonging to the nonbenzodiazepine group known as Z-drugs, and chemically it is a cyclopyrrolone ^[1]. It was developed by Rhone-Poulenc and first introduced in the mid-1980s, and it is sold under brand names including Imovane and Zimovane in Europe, Canada, and many other countries; it is not marketed as such in the United States, where its purified active enantiomer, eszopiclone (Lunesta), is sold instead ^[1][4]. When introduced it was promoted as an advance over benzodiazepines, a claim later disputed as its similarities to those drugs became clear ^[1].

The compound is prescribed for the short-term management of insomnia, covering difficulty both falling asleep and staying asleep ^[1]. It has a moderate elimination half-life of several hours, longer than that of the very short-acting Z-drugs, which contributes to effects on sleep maintenance but also to a greater chance of next-day carryover ^[1][4]. Zopiclone is a racemic mixture of two mirror-image molecules; eszopiclone is the isolated active S-enantiomer, and the two share the same cyclopyrrolone pharmacology ^[1][4].

Clinical guidelines and trials place zopiclone in context. Professional guidelines for chronic insomnia give only weak recommendations for Z-drugs and stress that the benefits are modest ^[3]. A randomized controlled trial in older adults found that cognitive behavioral therapy for insomnia produced better short-term and long-term sleep outcomes than zopiclone, which for most measures did not differ from placebo ^[2]. A well-recognized drawback is next-day impairment; on-the-road driving studies show that zopiclone, like benzodiazepine hypnotics, can significantly impair driving the morning after use ^[5].

Zopiclone is a controlled substance in many jurisdictions, reflecting a real potential for tolerance, dependence, and misuse that resembles that of benzodiazepines; abrupt cessation after regular use can trigger withdrawal and rebound insomnia ^[1]. A characteristic and frequently reported side effect is a bitter or metallic taste, along with drowsiness, dry mouth, and headache ^[1].

Zopiclone is genuinely effective, but it is a serious drug with a real dependence profile, which is why it is a controlled substance (Schedule IV in the US, and scheduled or prescription-only across most of the world) meant for short courses of two to four weeks. The most talked-about side effect is harmless but unpleasant: a bitter, metallic taste that can linger into the next day because the drug is secreted in saliva. More important are next-day drowsiness and impaired driving, dizziness, dry mouth, and headache. With regular use, tolerance and physical dependence can set in, and stopping abruptly can trigger rebound insomnia (sleep that is briefly worse than before you started) along with anxiety and, rarely, withdrawal seizures.

Like other Z-drugs it can cause complex sleep behaviors: walking, eating, texting, or even driving while not fully awake and with no memory of it afterward. The biggest danger is mixing it with other central nervous system depressants; alcohol, opioids, benzodiazepines, gabapentinoids, and sedating antihistamines all stack with zopiclone to deepen sedation and suppress breathing, and these combinations are a recurring thread in overdose deaths. Older adults are especially vulnerable to falls, confusion, and prolonged effects because they clear the drug more slowly.