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SMOKERS may find it easier to kick the habit with the help of a drug
originally developed to treat psoriasis, say Canadian scientists. Edward Sellers
and his colleagues at the University of Toronto knew that people whose bodies
have trouble breaking down nicotine are less likely to smoke. After screening
more than 200 compounds, they found one, methoxsalen, that blocks the enzyme the
body uses to metabolise nicotine.

Smokers get withdrawal symptoms when the level of nicotine in their blood
drops. So the Canadian team wanted to know if methoxsalen could delay the start
of withdrawal symptoms by preventing the breakdown of nicotine. They gave 17
smokers with normal nicotine metabolism either methoxsalen or a placebo,
together with a 4-milligram nicotine capsule, and then measured the nicotine in
their blood every 30 minutes for the next three hours. They found that people
who had been given at least 10 milligrams of methoxsalen had roughly twice as
much nicotine in their blood.

In a separate trial, the researchers gave 12 smokers either a placebo or 30
milligrams of methoxsalen together with nicotine. They found that smokers who
had taken methoxsalen and nicotine smoked 50 per cent less, waited longer
between cigarettes and took fewer puffs on each one.