Nicotine metabolizes faster in women than in men

NEW YORK (Reuters Health) – Women metabolize nicotine
faster than men do — especially women who are taking oral
contraceptives — according to a new report. The researchers
say this could affect women’s smoking behavior, as well as
their response to nicotine-based quitting aids.

Dr. Neal L. Benowitz from University of California, San
Francisco, and colleagues, compared nicotine metabolism in 88
men and 206 women, and compared the 53 women who used oral
contraceptives with the 153 who did not. For the investigation,
the subjects received an infusion of nicotine that was
“labeled” so it could be traced as it passed through the body,
which was followed by frequent blood sampling. The findings are
reported in the journal Clinical Pharmacology and Therapeutics

The rate of nicotine passage through the body was
significantly higher for women (18.8 mL/min/kg) than for men
(15.6 mL/min/kg), the investigators found. The rate was also
higher in women who were using oral contraceptives (22.5
mL/min/kg), compared with those who were not (17.6 mL/min/kg.)

By the same token, nicotine persisted in the body longer in
men (132 minutes) than in women not taking oral contraceptives
(118 minutes) and in women who were taking oral birth control
(96 minutes), the researchers note.

There seems to be a spectrum of nicotine metabolism time
that varies by level of female sex hormones, with metabolism
times progressing from slower in men, to intermediate in women
not on oral contraceptives, to faster in women taking oral
contraceptives, Benowitz and colleagues observed.

“Further research is needed to examine the question of
whether oral contraceptive use influences either smoking
behavior or intake of tobacco smoke from cigarettes (or both)
among women,” the team points out.

Because some studies have shown that the “success rates
with nicotine replacement therapies are lower in women than
men,” the researchers suggest that future studies should try to
identify the optimal dose of nicotine these products should
contain for women users.

SOURCE: Clinical Pharmacology and Therapeutics, May 2006.

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