TORONTO, Sept. 17 /CNW/ - Whether a smoking-cessation drug will enable
you to quit smoking may depend on your genes, according to new genotyping
research from the Centre for Addiction and Mental Health (CAMH). The study,
published in the September issue of the journal Biological Psychiatry, found
that the enzyme known to metabolize both the smoking cessation drug bupropion
and nicotine is highly genetically variable in all ethnicities and influences
smoking cessation. This finding is a step toward being able to tailor smoking
cessation treatment to individuals based on their unique genetic make-up.
"This first study identifies a very common genetic variant (present in
anywhere from 25 to 50 percent of world populations) that appears to affect
the outcome of smoking cessation treatment," said Rachel Tyndale, Section Head
of Pharmacogenetics at CAMH and lead researcher on the study, adding that the
results would have to be replicated.
Tyndale and colleagues performed genotyping on smokers for CYP2B6, a gene
known to be highly variable and whose enzyme metabolizes bupropion, nicotine
and serotonin. Participants were then provided with either placebo or
bupropion treatment for ten weeks and followed up for 6 months.
The research project, supported by the Canadian Institutes of Health
Research and the National Institute of Health, found that 45% of individuals
with a specific variant of the gene benefited from bupropion treatment and
maintained abstinence longer while doing poorly on placebo, with a 32.5%
abstinence rate vs. 14.3%, respectively. In contrast, the 55% with a different
variant of the gene (wild type variant) had good abstinence rates on placebo
and gained no additional benefit from Bupropion, suggesting no benefit from
treating these individuals with Bupropion. Of note, this group was able to
quit smoking very well in the absence of an active drug (on placebo).
What percentage of people fall into the group that appeared to benefit?
Previous studies have shown that 45%, 50% and 25% of White, African and Asian
North Americans have the former specific variant form of the CYP2B6 gene.
The current study looked only at people of European ancestry, says Dr.
Tyndale, but she and her colleagues have begun a similar study in African
American smokers. They hypothesize that the variant form of the CYP2B6 gene
will influence the effectiveness of bupropion treatment and ability to quit
smoking in the same way in African Americans as in those of European descent.
The Centre for Addiction and Mental Health (CAMH) is Canada's leading
addiction and mental health teaching hospital. Integrating clinical care,
scientific research, education, policy development and health promotion, CAMH
transforms the lives of people impacted by mental health and addiction issues.
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For further information: or to arrange interviews please contact Michael
Torres, Media Relations, CAMH at (416) 595-6015