Zopiclone

Zopiclone (sold as Imovane®, Zimovane®) is a novel hypnotic agent used in the treatment of insomnia. It was first developed by Sepracor and introduced in 1988 by Rhône-Poulenc S.A., now part of Sanofi-Aventis. Zopiclone is a controlled substance in the United States, Canada and some European countries and may be illegal to possess without a prescription.

While it acts on the BZ1 receptor and is a short-acting hypnotic agent, it is not a benzodiazepine, but a cyclopyrrolone derivative, belonging to a novel chemical class which is structurally unrelated to existing hypnotics.

On April 4, 2005, the DEA listed zopiclone under Schedule IV, due to some evidence that the drug has addictive properties similar to benzodiazepines.

Zopiclone, as traditionally sold worldwide, is a racemic mixture of two stereoisomers, only one of which is active. In 2005, the pharmaceutical company Sepracor began marketing the active stereoisomer eszopiclone under the name Lunesta in the United States. This had the consequence of placing what is a generic drug in most of the world under patent control in the United States. The eszopiclone/zopiclone difference is in the dosage - the strongest eszopiclone dosage contains 3-mg of the therapeutic stereoisomer, whereas, the highest zopiclone dosage (7.5-mg) contains 3.75-mg of the active stereoisomer. The two agents have not been studied via head-to-head clinical trials to determine if any clinical differences exist (eg. efficacy, side-effects, etc.).

Zopiclone is known coloquially as a 'Z drug', Other Z drugs include zaleplon and zolpidem and were thought in initial studies to be less addictive and less habit forming than benzodiazepines. This appraisal has shifted somewhat in the last few years, as cases of addiction and habituation have been presented. It is recommended that zopiclone is taken on a "when required" basis, and daily or continuous use of the drug is not usually advised.

Adverse reactions

The side-effect most commonly seen in clinical trials is taste alteration or dysgeusia (bitter, metallic taste).

More common reactions:

Gastrointestinal: bitter metallic taste, dry mouth. Nervous system: drowsiness, headaches, fatigue.

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