Are you still smoking?” the GP asks, after examining your ear infection and scrolling through your medical notes. You sheepishly admit that you are - though you’ve been trying to cut down over the past few months and no longer join the miscreants behind the bike sheds. You leave the surgery not only with a prescription for some ear drops but also with a prescription for Zyban - a new drug that is supposed to take away your craving for cigarettes and help you through the pain of quitting.

Earlier this month, to coincide with National No Smoking Day, the Government went on the offensive against the evil weed. It announced that nicotine replacement therapies (including gum, inhalers and patches) were to become available on the NHS for the first time since they went on the market, 20 years ago. But Zyban, which doctors were already free to prescribe, opens up a whole new front in the battle. No one knows exactly how it works, but it does seem to help when you “just have to have a cigarette”.

Zyban (bupropion hydrochloride) was first marketed in the United States as an antidepressant under the trade name Wellbutrin. But psychiatrist Linda Ferry noted that many of her patients prescribed it had given up smoking or no longer enjoyed a cigarette. She carried out trials, with promising results. GlaxoSmithKline, which marketed the drug, ran its own trials and relaunched it in the US as an anti-smoking aid as well as an antidepressant.

Last June, the Medicines Control Agency licensed it for use in the United Kingdom to help people stop smoking (it is not licensed in the UK as an antidepressant). Its release coincided with the nationwide launch of the Government’s National Smoking Cessation Service, first mooted in a White Paper in l998. Labour pledged pound;60 million to establish a free treatment service in all health authorities to help people quit smoking. In 1999 the scheme was piloted in selected health action zones, and by 2000 it had been extended across the UK.

All health authorities have been issued with no-smoking guidelines and targets, and instructions to provide free clinics or counsellors - such as pharmacists or nurses. They are paid to provide a discrete service rather than one that is bolted on to other duties. GPs and hospital doctors are anxiously trying to recruit as many potential “quitters” as possible (an estimated 120,000 people die of smoking-related diseases in the UK each year; up to 3 million worldwide).

But Zyban does not come without side-effects Insomnia is perhaps the most common, and the drug is not prescribed for anyone who is already on antidepressants, is pregnant, is withdrawing from alcohol dependency, is epileptic or has suffered a head injury. The Department of Health is also monitoring Zyban’s safety after doctors reported that, since the drug was introduced, 18 people taking it in the UK had died. “The contribution of Zyban to these deaths is unknown,” says a spokesman for the department. “Patients may be required to stop smoking because of underlying diseases and these may explain some of the reported deaths.”

About 270,000 people in the UK have now been prescribed Zyban, which is taken for up to eight weeks. For the first few days, the dose is 150 milligrams (one pill) daily; this is then increased to two a day. By the second week a “quit day” must have been established.

If the treatment fails it is pointless starting again straight away. According to Professor Robert West, author of The National Smoking Cessation Guidelines for Health Professionals, there is “about zero chance of success” unless you wait at least a few months before starting another treatment cycle.

There is no strong evidence that Zyban is any more effective than nicotine replacement therapy (see box). One study reporting much better results with Zyban than with nicotine replacement was widely publicised when Zyban was launched as a non-smoking drug. But, as Clive Bates, director of anti-smoking group ASH, warns: “Until more studies have been done, it is too soon to make comparisons.”

Nevertheless, says Robert West, Zyban is “another weapon in our armoury and it may have unleashed some pent-up demand. It has certainly raised the profile of smoking and quitting - and that is a good thing.”

Saffron Davies is a senior lecturer at St George’s Hospital medical school, south London

HARD TO QUIT

There are 13 million smokers in the UK, with men just outnumbering women. Teenage girls smoke more than boys, but the boys catch up by the time they are 19. It’s not easy to give up - about 2 per cent of smokers succeed without any support or medication, 10 per cent with counselling, and about 20 per cent with counselling, plus nicotine replacement or Zyban.

The Government’s target is to reduce the number of smokers by about 20,000 a year - less than 0.2 per cent of smokers. Prescriptions of Zyban come in four-week treatment packs, so eight weeks’ treatment costs two standard prescription charges, less than one week’s supply of transdermal nicotine.

The cost to the NHS of a course of Zyban, plus telephone support, is around pound;86.

NHS Smoking Helpline: 0800 1690169. Quitline: 0800 002200