A study released today examined 6,363 U.S. Food and Drug Administration (FDA) adverse drug reaction reports implicating Pfizer's quit smoking pill Chantix (varenicline) and found that 3,063 involved serious injuries. Its recommendation? "We recommend that patients and doctors exercise caution in the use of varenicline and consider the use of alternative approaches to smoking cessation."
Authored by The Institute for Safe Medication Practices (ISMP), a non-profit medication watchdog, ISMP looks for safety flags while monitoring all adverse events reported to the FDA for all medications.
ISMP monitoring noted that "by the 3rd quarter of 2007 varenicline produced a signal not previously seen for any other drug. It produced more serious reports than any other drug for multiple types of events: more potential cases of angioedema, cardiac arrhythmia, diabetes and severe cutaneous injury. By the 4th quarter of 2007 varenicline accounted for more reports of serious drug adverse events in the United States than any other drug."
During the 4th quarter of 2007 the FDA received 998 reports of serious varenicline adverse events compared to only 372 for the addictive troublemaker oxycodone, a potent medication for relief of moderate to severe pain. While ISMP estimates that a total of 3.5 million Chantix (varenicline) prescriptions were written in the U.S. since FDA approval in May 2006, government estimates place annual oxycodone prescriptions written at more than 7 million.
The study found that while the FDA has issued warnings regarding Chantix's link to suicidal acts, thoughts or behaviors, psychosis, hostility and aggression, it has ignored "other kinds of serious harm for which no warnings now exist, either from the FDA or from the manufacturer, Pfizer Inc."
While the FDA received 78 death reports in which "varenicline was the principal suspect drug," only 28 resulted from suicide. There were "numerous reports suggesting cardiac causes, both thromboembolic and arrhythmic," writes ISMP.
Among reports of serious events were 173 accidents and injuries, 338 angioedemas, 224 cardiac arrhythmias, 86 convulsions, 139 embolic and thrombotic events, 372 extrapyramidal syndromes, 544 cases of hyperglycemia/new onset diabetes mellitus, 525 reports of hostility/aggression, 397 psychosis and psychotic disorders, 227 reports of suicide/self-injury, 65 severe cutaneous adverse reactions, and 148 vision disturbances.
Could there possibly be a common thread among such a diverse group of disorders? Yes, says the ISMP study. A subtype of acetylcholine receptor known as alpha 4 beta 2 plays "numerous roles in the brain and body and is central to muscle contractions -- both voluntary movement and heart muscle contractions, as well as the tone of the smooth muscles that line the blood vessels."
According to the study, Pfizer researchers found that varenicline was most active against alpha 4 beta 2 type acetylcholine receptors. They focused on the fact that it caused the release of dopamine within the brain while blocking nicotine from occupying alpha 4 beta 2 receptors. It notes that "many antipsychotic drugs block dopamine receptors, but they also cause movement disorders. The loss of muscle control seen in Parkinson's disease is the result of the destruction of dopamine-producing cells in the brain."
The gravity and number of serious injuries attributed to Chantix caused the report to lightly touch on an equally pressing risk analysis concern, the value of Chantix in helping smokers quit. While noting that counseling rich varenicline clinical trials produced 52-week quit rates of approximately 22 percent, it cites two early nicotine gum studies while noting that they achieved comparable rates.
In fact, a 1976 nicotine gum study headed by Russell found that 23% of nicotine gum users were still not smoking at 1 year. The 1980 nicotine gum study by Raw produced a whopping 38% rate, in 1982 Jarvis found a 31% rate, in 1983 Schneider 30%, in 1984 Hialmarson 29%, in 1986 Daughton 31%, in 1987 Kornitzer 32%, and in 1989 Tonnesen boasted a 44% one year quit smoking rate.
What wasn't mentioned in the ISMP study was that in real-world competition, outside of clinical trials that were rich in support and counseling, nearly all quitting method surveys to date show that, long-term, cold turkey quitters actually perform better than users of nicotine gum, patch, lozenge and Zyban.
A 2006 National Cancer Institute quitting method survey of 8,200 smokers found that at 9 months 16% of "on your own" quitters were still not smoking compared to just 14% among quitters relying upon the nicotine patch, gum, lozenge or Zyban.
While ISMP faults the FDA for neglect in warning Chantix users about risks other than mental and emotional, just as culpable is its approval of Pfizer's clinical trial design when: (1) they involved a record number of provider counseling/support contacts (twenty-five), contacts the FDA knows could account for nearly all effectiveness seen; (2) no assessments to test study blinding was requested or conducted, when the FDA knows that it is probably impossible to blind drug addiction studies, as smokers with any quitting history recognize the onset of full-blown nicotine withdrawal; (3) excluded 28% of study applicants, including nearly all having any significant medical condition, and then permitted Pfizer to market Chantix to groups intentionally excluded; and (4) allowed NRT use between the end of treatment and week 52, and then certified ongoing NRT users as having been successful Chantix quitters.
If Pfizer knows, via real-world quitting data gathered through its www.GetQuit.com website, that Chantix's real-world effectiveness is substantially less than shown in clinical trials, with Chantix injuries so numerous and serious, does Pfizer have both legal and ethical duties to immediately share that data with both the FDA and smokers considering using Chantix?
If Chantix isn't living up to Pfizer marketing hype, do reports like this ISMP study obligate Pfizer to be more forthright, honest and clear about both varenicline's safety and effectiveness?
"These data provide a strong signal that the risks of varenicline treatment have been underestimated, and show that a wide spectrum of serious injuries are being reported in large numbers," ISMP warns.
"Table 1 shows that in the 4th quarter of 2007, the other highest ranked drugs (e.g. fentanyl, interferon beta, etanercept) are all high alert drugs with black box warnings, are intended for serious illness in patients and have benefits that are accompanied by substantial risks. In comparison, varenicline is intended for use in healthy people to help stop smoking."
Does it make sense, if inside a very slow burning building, to pay money for the right to use the most dangerous exist path out?
Never in the history of smoking cessation has any quitting product harmed so many. It makes one wonder whether instead of helping smokers the FDA and Pfizer have declared war upon them.
XXX
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John R. Polito is solely responsible for the content of this article.
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