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Chantix efficacy: the studies and the real world
The FDA took Chantix' efficacy at face value from the manufacturer's trial studies, claiming that Chantix significantly improves the chances for nicotine addicts to quit smoking, compared to both, other smoking-cessation therapies ("nicotine replacement therapy" - nicotine patches, gums, etc. - and prescription drug Zyban), and quitting without drug therapy. But how relevant are these figures for the actual user environment?
Specifically, Pfizer claims - based on their pre-marketing trials resulting in 45% and 20% quitting rates after 12 weeks and 1 year, respectively - that the chances of quitting smoking after a year are up to 33%, and up to 3 times better with Chantix, than with Zyban, or no therapy, respectively.
It shouldn't be surprising if Chantix has performed somewhat better than Zyban, originally antidepressant plagued with possible serious side effects. The effectiveness of the latter is limited by safety concerns, due to its seizure-causing capability increasing exponentially with the dosage (for that reason, it was temporarily withdrawn from the market, until "acceptably" dangerous dosage limit was established).
A brand new, 2008 Aubin study, similar to Pfizer's pre-marketing trials in hand-picking the participants and providing intense support, including periodic counseling, came up with 1-year quitting rate with Chantix 30% better than with stepped-down nicotine patch use (26% vs. 20%). Not much of a difference, but the numbers are still in favor of Chantix.
So far so good. But how these same drugs would perform in the real world, where "participants" - unlike the studies - include sick, troubled, unstable, those least likely to quit, and where there is no constant support to keep you going? A look at relatively recent history of related studies gives some indications.
Several clinical trials in the 1976-89 period came up with 1-year quitting rate with the nicotine gum in 23%-44% range. And how did it work in the real world? A 2003 meta-study (Hughes) of several over-the-counter (real-world) success rate for both, nicotine gum and patch, had established a
7% 6-month quitting rate.
Realistic 1-year projection would be even lower. This is only a small fraction - roughly one sixth - of the success rate claimed by the clinical studies.
If the similar ratio is applied to the Chantix' study success rate, its real-world effectiveness would be at the level of 5% 6-month quitting rate at best. Quite a bit lower than the comparable rate of quitting on your own, which is, according to the 2000 U.S. Tobacco Cessation Guideline, between 10% and 15%.
Wide discrepancy between clinical and real-world effectiveness of smoking-cessation therapies results not only from tailoring both, selection of participants and conditions favorable to the desired outcome, but also from the the inherent flaws. It is only logical that the majority of those attracted to participation in this type of studies have decided that they need a pill to help them quit smoking. This by itself results in an
participant profile bias against those
Furthermore, it is no secret that most of the participants in quit-smoking studies can determine, rather quickly, whether they are receiving an effective agent, or placebo (presenting these type of studies as "blind" is both, silly and misleading). It is a simple human psychology - in addition to greater suffering from withdrawal symptoms - that makes those realizing that they are on placebo more likely to fall back on their nicotine fix.
Also, the success rate here can be greatly influenced by the criteria applied. For instance, in some of the studies, use of some form of nicotine replacement therapy (or, for that matter, even plain smoking) wouldn't disqualify participants from being considered abstinent, as long as their carbon monoxide level was O.K. at the time of measurement - something that could be accomplished with as little as a few hours of abstinence prior to the test.
In other words, most any study participant who wants to show as a successful quitter, would likely be able to do so regardless of his or her actual status.
While Pfizer and others tirelessly paint the picture of one's chances to quit smoking without drug therapy being poor, and significantly lower than when using their products, actual data disagrees. According to the 2003 American Cancer Society figures,
over 90% of former
smokers have quit on their own,
Why do both, FDA and FTC (Federal Trade Commission) allow drug companies to use these misleading marketing tactics? Well, that could be a "zillion dollar question"...
At present, Pfizer is responding to the pressure resulting from bad publicity by partly disclosing possible adverse health effects of Chantix to the consumer and doctors-alike. And the FDA is getting busy creating impression that it is doing its job. Still, looking at all the figures - as scanty and incomplete as they are - one can't escape impression that, contrary to the marketing claims,
the efficacy of
Chantix (and nicotine replacement therapy)
On the other hand, its possible serious adverse health effects are real and significant. It is good to know that.
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