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Are the 'Z-drugs' really carcinogenic?

Posted by Quintal on July 2, 2008, at 11:30:14

I've been coming across these sinister articles for a while. They seem to suggest that 'z-drugs' are associated with higher rates of cancer mortality. The FDA has expessed skepticism over the validity of these studies because of the short time lag between exposure and diagnosis (as little as fourteen days in one case, and all within six months). Also, the authors found that ramelton (Rozerem) carried a significant risk of cancer mortality despite having a completely different mechanism. I'm wondering why hypnotics as a class were singled out for investigation, rather than a chemical class i.e. benzodiazepines? This obviously raises questions as to whether the older benzos carry similar risks. As it is I'm not too concerned, but I am considering switching my zopiclone to lormetazepam (pdoc permitting), or even a nightly dose of diazepam.

Evidence That New Hypnotics Cause Cancer
Daniel F. Kripke, University of California, San Diego
March 17, 2008

Fifteen epidemiologic studies have associated hypnotic drugs with excess mortality, especially excess cancer deaths. Until recently, insufficient controlled trials were available to demonstrate whether hypnotics actually cause cancer. The U.S. Food and Drug Administration (FDA) Approval History and Documents were accessed for zaleplon, eszopiclone, and ramelteon. Since zolpidem was used as a comparison drug in zaleplon trials, some zolpidem data were also available. Incident cancers occurring during randomized hypnotics administration or placebo administration were tabulated. Combining controlled trials for the 4 drugs, there were 6190 participants given hypnotics and 2535 given placebo in parallel. Restudy of on-line FDA files led to somewhat altered counts of incident cancers, which are currently being checked against an FDA case review. FDA files revealed that all 4 of the new hypnotics were associated with cancers in rodents. Three had been shown to be clastogenic. Combining these new randomizing trials provided equivocally- significant data that new hypnotics cause cancer. Together with the epidemiologic data and laboratory studies, the available evidence signals that new hypnotics may increase cancer risk. Due to limitations in available data, further review of case files for these trials and confirmatory research is needed.

Daniel F. Kripke, "Evidence That New Hypnotics Cause Cancer" (March 17, 2008). Department of Psychiatry, UCSD. Paper 3.

Full article (PDF document):


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]

The zopiclone study was carried out on a group of HIV positive men, and the cancers were mostly Kaposi's sarcoma - hardly unusual for that population. I sense a whiff of scaremongering among all this, but posibly a grain of truth. I can't help but wonder how many other psychiatric drugs would show a similar relationship with cancer mortality if studied in the same way though.





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