Smokers who try to quit using existing medications, such as nicotine patches or Zyban, are about twice as likely to succeed as those who don't use medication or are prescribed placebos during clinical trials.
But despite the relative effectiveness of medications currently on the market, more than 80 per cent of quitters will be smoking again within a year, according to a review in the latest IJCP, the UK-based International Journal of Clinical Practice.
A new kind of drug has now been developed that could improve long-term quit rates, according to Dr Jonathan Foulds from the Tobacco Dependence Program at the University of Medicine and Dentistry of New Jersey.
Varenicline is being evaluated by the US Food and Drug Administration under a six-month priority review which began in late 2005.
"Trials carried out so far have yielded promising results, suggesting that varenicline could be a major advance in the treatment of nicotine dependence" says Dr Foulds.
"Drugs are normally earmarked for priority review by the FDA if they are felt to address health needs that are not currently being adequately met.
"What makes varenicline different to existing medication is that it is the first treatment specifically designed to target the neurobiological mechanism of nicotine dependence."
Initial results show that the drug successfully stimulates dopamine -- sometimes called the brain's pleasure chemical -- as well as blocking nicotine receptors. This reduces nicotine withdrawal symptoms and craving and may also prevent a lapse from turning into a full relapse.
Existing quit smoking methods have limited success and studies have found that some 18 per cent of people using them will be smoke free after a year, compared with 10 per cent of people prescribed placebos.
This figure can be increased to 25 to 35 per cent when smokers receive intensive counselling and combined medications are used.
Dr Foulds summarised 141 studies covering just over 48,000 subjects who were randomly allocated different types of medication or placebos.
He found that quit rates with nicotine replacement methods and drugs such as bupropion (trade name Zyban), nortriptyline and clonidine ranged from 14.6 per cent to 24.9 per cent. Smokers who were prescribed placebos (dummy drugs) achieved success rate of between 8.6 per cent and 14.4 per cent.
But clinical trials carried out with varenicline on thousands of smokers suggest that the new drug yield may yield better success rates.
The results of human trials reported in 2005 and 2006 found that short and long-term quit rates were higher when compared with placebos or bupropion (Zyban).
Studies presented at recent scientific meetings have shown that short-term quit rates in the first 12 weeks were approximately four times higher with varenicline than placebos and that long-term abstinence rates, for the first year, were more than twice those of placebos.
"Almost 20 countries and numerous US states have already announced or implemented comprehensive indoor smoking bans and that figure is rising all the time" adds Dr Foulds.
"Here in New Jersey, for example, smoking is very expensive and we have just implemented comprehensive legislation to ban smoking indoors in virtually all pubic places.
"This is good news for smokers and non smokers alike as many smokers are keen to quit and this gives them an added incentive.
"Medicines like varenicline are very important as they will help many more people to quit smoking, including those who have failed with other methods."
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