The drug varenicline (Chantix) quadrupled the success rate of people trying to I quit smoking, according to three recent studies. Approved by the US Food and Drug Administration (FDA), Chantix was also found to be twice as effective as bupropion (Zyban), another smoking-cessation drug.

The research-all of which was funded by the drug's maker, Pfizer Inc.-is encouraging, experts say, because smokers do not have many medications that are useful in helping them quit.

Unlike Zyban and nicotine-replacement methods (patches and gums), Chantix works by stimulating the release of the brain chemical dopamine, to reduce cravings, while simultaneously blocking the brain cell receptors that help sustain addiction.

Two Studies

In one study, researchers led by David Gonzales at the Oregon Health & Science University in Portland, compared the effectiveness of Chantix, Zyban and a placebo in helping 1,025 adult smokers quit over the course of one year.

After 12 weeks, 44% of the people taking Chantix had been smoke-free for at least one month, compared with 29.5% of those taking Zyban and just under 18% of those in the placebo group, the researchers report.

Long-term quit rates were lower, however. The rate of "continuous abstinence" from week nine to the one-year mark was just under 22% for Chantix, approximately 16% for Zyban, and 8.4% for the placebo.

A second, similar trial led by Douglas Joren by of the University of Wisconsin found almost identical results.

The Third Study

A third trial of more than 1,900 smokers living in seven countries looked specifically at relapse rates after quitting.

All of the smokers first underwent 12 weeks of Chantix therapy. Approximately two-thirds (1,236) were deemed to have kicked the habit by the end of the three-month period.

The researchers then gave these "quitters" either Chantix or a placebo daily for the next 12 weeks.

By the end of the 24-week study period, 70.5% of the people who continued on Chantix remained nonsmokers, compared with 49.6% of those taking a placebo for the second 12 weeks..

By the end of the 24-week study period, 70.50/o of the people who continued on Chantix remained nonsmokers, compared with 49.50/0 of those taking a placebo for the second 12 weeks.

'An additional 12 weeks of treatment was more beneficial than placebo," says lead researcher of the study, Dr. Serena Tonstad, an attending physician in the department of preventive cardiology at Ulleval University Hospital in Oslo, Norway.

'Not A Panacea'

Robert Klesges and his colleagues at the University of Tennessee Health Science Center in Memphis say that when a new smoking-cessation aid gets FDA approval, "there is often unbridled enthusiasm regarding the potential to solve the problems associated with smoking." However because of high rates of both side effects and treatment failure, Chantix "definitely is not a panacea for smoking cessation."

While on Chantix, almost 30% of the trial participants reported nausea, and many others experienced "abnormal dreams."

Dropout rates were also high, although that is consistent with what is usually seen in smoking cessation trials.

In the Norwegian trial, only those smokers who had quit by 12 weeks were allowed to enter the second, relapse-focused phase of the trial. "The authors have eliminated [from their analysis] approximately one-third of individuals for whom this drug does not appear to be effective," the Tennessee experts note.

Finally, they say, all of these Pfizer-funded trials took place under the very best conditions-at academic research centers where smokers were closely monitored and instructed on the proper use of the drugs. That's quite different than a "real world" situation where the average smoker is given a prescription and then left more or less on his/her own.

So, while the results of these trials are promising, nicotine addiction remains a tough challenge. In fact, "the majority of participants in these three studies did not quit smoking-even with varenicline," the experts point out.

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