A simple genetic test could help doctors tailor anti-smoking treatments to patients' needs, making it easier for them to quit.

The test allowed an Oxford University team to successfully predict which smokers would respond well to nicotine patches, and which wouldn't. The test is for common mutations in genes that control the metabolism of dopamine. Nicotine stimulates the production of dopamine in the nucleus accumbens, the brain's "pleasure centre". People with these mutations metabolise dopamine more quickly. They would therefore benefit from anti-smoking treatments that are designed to boost dopamine levels. But they are less likely to respond well to nicotine-replacement therapies, such as nicotine patches, says the team. John Stapleton of the National Addiction Centre in London finds the work interesting, but warns: "They are only looking at a few genes and there are potentially dozens involved. This is only part of the story." Tailored treatment The team found that a person's genotype affects not only whether they are likely to smoke or not, but how many cigarettes they consume. Between 30 and 40 per cent of people have mutations in genes that code for two enzymes involved in dopamine metabolism: dopamine-hydroxylase and monoamine oxidase. Heavy smokers are two to three times as likely to have mutations in these genes as non-smokers, says Robert Walton, one of the Oxford researchers. People with these mutations need to smoke more to maintain normal dopamine levels, so should be targeted with dopamine-boosting drugs such as buproprion, Walton says. Smokers without the mutations are more likely to be fast metabolisers of nicotine, and could be given nicotine patches. Nicotine replacement therapy is currently the most popular form of anti-smoking treatment, says Walton. "It's the most effective treatment, but the success rate is still only about 20 per cent. So if it doesn't work for you, you get pretty disheartened." In one study, the team found they could predict which of 800 smokers would respond to the patches. They are currently writing up these results for publication. Walton hopes the DNA test could be widely available in two to three years' time.

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