The first drug designed to help smokers quit without the use of nicotine has been licenced for use in the Scottish NHS.

The Scottish Medicines Consortium (SMC) is due to announce today that it has approved Champix after clinical trials showed that nearly half of smokers given the drug were able to give up their habit.

The decision has been welcomed by charities and medical experts who yesterday described Champix as a significant step forward in the therapies made available for British smokers. It puts Scotland ahead of England, where guidance on the use of the drug is due to be published later this year.

Unlike nicotine replacement therapies (NRTs) such as patches, which release nicotine into the blood, Champix, whose technical name is varenicline tartrate, provides relief from withdrawal symptoms by sending a neurological signal to nicotine receptors in the brain.

By stimulating these receptors, smokers are provided with relief from their cravings. However, the drug also partially blocks the same receptors, ensuring that if a patient relapses they will not receive the same level of pleasure from smoking a cigarette.

Steve Crone, chief executive of Quit, a charity which helps people give up smoking, welcomed the SMC's decision.

He said: "Varenicline will give Scottish smokers more choice from a good range of clinically proven treatments. Using varenicline and getting the right support could significantly increase a smoker's odds of successfully quitting."

Champix is the second non-nicotine drug to be licensed as a therapy for smokers in the UK. Its predecessor, Zyban, which was licensed in June 2000, was designed as an anti-depressant.

It is thought to work by regulating the brain chemicals dopamine and noradrenaline, which are believed to be linked to cigarette addiction and has been claimed to be twice as effective as NRT therapies in helping people to give up.

However, Champix has proved more effective and less likely to produce adverse side effects than its predecessor.

As part of its assessment of Champix, the SMC used data from two studies which involved more than 2000 smokers. It studied three groups who were given Champix, Zyban and a placebo.

Among the patients given Champix, which is administered as a tablet, 44% were able to give up smoking, compared with 30% of those given Zyban and 18% of those given a placebo. After 12 weeks, smokers taking the new drug had four times greater odds of stopping smoking than those on a placebo and two times greater odds of stopping than those on Zyban, the studies found. Clinical trials have also found that, among 4000 smokers who were treated with the drug, the number of treatments that had to be discontinued due to adverse effects was similar to those treated with a placebo.

Dr Alex Bobak, a London-based GP and expert on quitting smoking who has been involved in trials of Champix, said he had found the drug effective with patients who wanted to give up smoking.

"It is the first drug that has been designed for the purpose of giving up smoking. I have trialled it with patients and have certainly found it extremely helpful," he said.

"One of the big differences from Zyban is that it is much better tolerated, there are much fewer side-effects. I'm very excited about using it."

A spokesman for Ash Scotland, which campaigns against smoking, said: "We would welcome the introduction of any properly tested and licensed treatment that can help Scotland's smokers to quit.

"There is a huge challenge in Scotland, where around 13,000 people die every year because of tobacco use."