"Zopiclone may be carcinogenic and mutagenic according to rat, mice and hamster studies. It should be noted that, at 100 mg per kg of bodyweight per day, the dosage was considerably higher than the therapeutic dose for humans. The authors of an uncontrolled study of Zopiclone said that it may take decades in immunocompetent people before carcinogenic effects from past zopiclone use develops. It was suggested that further research and monitoring was required into the potential for zopiclone to cause cancer in immunocompetant patients.[1]
A recent analysis of FDA and clinical trial data shows that nonbenzodiazepine Z-drugs at prescribed doses cause cancer in humans. The data shows that trial subjects receiving hypnotic drugs had an increased the risk of developing cancer and malignancies. There have been 15 epidemiologic studies which have shown that hypnotic drugs cause increased mortality, mainly due to increased cancer deaths. The cancers included, cancer of the brain, lung, bowel, breast, and bladder, and neoplasms. Initially FDA reviewers did not want to approve the drugs due to concerns of cancer but ultimately changed their mind and approved the drugs despite the concerns. FDA data has shown that zolpidem, zaleplon and eszopiclone are clastogenic and cause cancer in rodents. Benzodiazepine agonists are associated with an increased risk of ovarian cancer in humans. Zopiclone was reportedly refused a product license by the FDA in the USA due to indications that zopiclone caused cancer. Development of a malignant neoplasm has been associated with zolpidem usage but the rate of incidence of neoplasm in zolpidem users is as yet unknown. The rates, in clinical trials for the nonbenzodiazepine Z drugs, of malignancies and neoplasms are significantly higher in hypnotic groups than in placebo groups. Also the analysis of clinical trials and FDA data showed that eszopiclone, zaleplon, and zolpidem appeared to have an adverse effect on the immune system causing an increased rate of infections and colds in hypnotic users. Suppression of immune function might be the cause of the increased rate of cancer in nonbenzodiazepine hypnotic users. Indiplon has also shown an increased rate of cancers in clinical trials. The review author concluded saying; "the likelihood of cancer causation is sufficiently strong now that physicians and patients should be warned that hypnotics possibly place patients at higher risk for cancer".[2]"
[1] Stebbing J; Waters L, Davies L, Mandalia S, Nelson M, Gazzard B, Bower M (1). "Incidence of cancer in individuals receiving chronic zopiclone or eszopiclone requires prospective study". J Clin Oncol 23 (31): 8134?6. doi:10.1200/JCO.2005.03.5881. PMID 16258120.
http://jco.ascopubs.org/cgi/content/full/23/31/8134
[2] Kripke, Daniel F (2008). "Evidence That New Hypnotics Cause Cancer" (PDF). Department of Psychiatry, UCSD. University of California. ?the likelihood of cancer causation is sufficiently strong now that physicians and patients should be warned that hypnotics possibly place patients at higher risk for cancer."
http://jco.ascopubs.org/cgi/content/full/23/31/8134
Original Article:
http://en.wikipedia.org/wiki/Zopiclone