July 8th 2006
A NEW drug that reduces the craving for cigarettes and abates withdrawal symptoms appears to be more effective in helping people break the smoking habit than the best therapy currently available, the nicotine-replacement drug bupropion (Zyban), according to three new studies.
But although the new anti-smoking drug, varenicline, is seen as a step forward, experts caution that it is less effective than health officials would like, and that there may never be a pill to help most smokers quit.
"Varenicline definitely is not a panacea for smoking cessation," Robert Klesges of the University of Tennessee Health Science Centre wrote in an editorial accompanying the studies in the Journal of the American Medical Association.
"Many participants in these trials experienced adverse events, stopped taking their study medication before they should have, and discontinued participation in the studies. Importantly, the majority of participants in these three studies did not quit smoking even with varenicline." The drug, approved by the US Food and Drug Administration in May, is expected to be available by August in America, marketed under the trade name Chantix. But it is not expected to become available in Australia for a couple of years.
Two of the studies in JAMA involving more than 2,000 smokers found that 44 per cent of people taking varenicline for up to 12 weeks continued to abstain from smoking. This compared with about 30 per cent for bupropion, or Zyban, and 17 per cent for those taking an inert placebo. After 52 weeks, 22 to 23 per cent of those on varenicline were still not smoking compared with 14 to 16 per cent taking bupropion.
Only eight to 10 per cent of smokers on placebos were still abstinent after one year. Pfizer, which will manufacture varenicline, supported all of the studies.
Nicotine-replacement compounds such as bupropion and patches are commonly used to help people quit, but success is only moderate.
Varenicline is a non-nicotine drug that appears to work by stimulating the production of dopamine, the brain's reward chemical, said David Gonzales of the Oregon Health and Science University, who led one of the studies published this week. The drug reduces a person's desire for a cigarette, blunts withdrawal symptoms and, for those who do smoke, blocks the reinforcing effects of cigarettes.
Gonzales and the author of the other study, Douglas Jorenby of the University of Wisconsin School of Medicine and Public Health, said varenicline appeared to be well tolerated and that the major side effect was nausea.
The third study, conducted by Dr Serena Tonstad of Ulleval University Hospital in Oslo, Norway, found that a booster round of varenicline helped increase the smoking abstinence rate of quitters.
"Clearly, quitting smoking, even with pharmacological and behavioural assistance, is extremely difficult," Klesges wrote in the editorial. "Patients currently cannot and probably never will simply be able to 'take a pill' that will make them stop smoking."
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