Smokers who try to quit using existing medications, such as nicotine patches or GlaxoSmithKline’s Zyban (bupropion), are about twice as likely to succeed as those who don’t use medication or are prescribed placebos during clinical trials.

But despite this initial success rate more than 80% of quitters will be smoking again within a year, according to a review in the International Journal of Clinical Practice.

The review, authored by Dr Jonathan Foulds from the Tobacco Dependence Programme at the University of Medicine and Dentistry of New Jersey, said a solution to this problem could around the corner in the shape of varenicline, a new kind of drug developed by Pfizer.

Varenicline is being evaluated by the US Food and Drug Administration under a six-month priority review which began in late 2005, and analysts have said the drug could achieve sales of between $500 million and $1 billion a year at its peak.

“What makes varenicline different to existing medication is that it is the first treatment specifically designed to target the neurobiological mechanism of nicotine dependence,” according to Foulds.

Initial results show that the drug successfully stimulates 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, with studies suggesting that around 18% of people using them will be smoke free after a year, compared with 10% of people prescribed placebos. This figure can be increased to 25% to 35% when smokers receive intensive counselling and combined medications are used.

But clinical trials carried out with varenicline on thousands of smokers suggest that the new drug 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 placebo or Zyban, he noted.

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 placebo and that long-term abstinence rates, for the first year, were more than twice those in the control group.