A drug that targets the pleasure-inducing chemical in the brain to help smokers give up has been introduced in Hong Kong. The drug, Zyban, was launched in the territory about a week ago and is being used by about 40 smokers. Manufacturer Glaxo Wellcome claimed the drug had a 30 per cent success rate in a clinical trial involving 900 smokers in the United States, compared to 15 to 16 per cent success with more conventional treatment. The prescription drug was first introduced in the US three years ago. Zyban targets two brain chemicals, including dopamine, which is linked to feelings of pleasure. Smoking lowers the release of dopamine, so smokers have to inhale more to bring the levels up. The drug helps stimulate the release of dopamine. Conventional approaches encourage smokers to reduce nicotine intake gradually. Dr Robert Peter Young, senior lecturer and consultant physician at the University of Auckland in New Zealand, said the new drug was found to be twice as effective as a nicotine patch. He said smokers using nicotine patches or gums would probably relapse on average five times before they could succeed in giving up the habit. Dr Young said he was not worried that people would be reluctant to use the drug to stop smoking because of the temporary side effects. 'Smokers are taking drugs already as there are 4,000 chemicals in a cigarette. It is just a matter of a trade-off,' he said. A full course of treatment with Zyban takes about eight weeks. It involves taking two tablets a day, subject to doctors' consultation. In the first few days, smokers can feel dryness in the mouth and minor sleep disturbance, but the drug manufacturer claims this will wear off. Excluding a consultation fee, the eight-week treatment would cost about $2,000. Conventional nicotine gum costs about $300 a box for 75 pieces of gum. It is estimated that there are about 805,100 people who smoke daily in Hong Kong, representing about 15 per cent of people aged 15 and over. The manufacturer has also set up a telephone hotline answering queries on the use of the new drug and providing counselling services.