Koren Gideon, Blanchette Phillip, Lubetzky Angelika, Kramer Michael
Division of Clinical Pharmacology/Toxicology, The Hospital for Sick Children, Toronto, Ontario, Canada.
Ther Drug Monit. 2008 Apr;30(2):246-8. doi: 10.1097/FTD.0b013e318167d05b.
A large number of smoking women cannot quit their habit when they become pregnant. Preliminary evidence suggests an enhanced nicotine clearance rate in late pregnancy. To evaluate the change in nicotine metabolism in late pregnancy, we undertook a prospective cohort study of a large, diverse group of pregnant women recruited from four Montreal maternal hospitals. Smoking histories were obtained by structured questionnaires administered at 24 to 26 weeks of gestation and postpartum. Hair concentrations of nicotine and cotinine were measured by immunoassays for each trimester based on sectioning the hair and assuming average hair growth of 1 cm per month. A strong correlation was observed between average number of cigarettes smoked per day and hair nicotine and cotinine in all three trimesters. A significant decrease in hair nicotine was observed among steady smokers from the first to third trimester paralleled by a significant increase in hair cotinine. The ratio of hair nicotine:cotinine decreased significantly from the first to the third trimester. Increased nicotine metabolism in late pregnancy results in lower systemic exposure to nicotine. This phenomenon may explain why many pregnant women feel the urge to continue smoking and why standard-dose nicotine replacement therapy has not been effective in reducing smoking during pregnancy in several clinical trials.
许多吸烟女性在怀孕后无法戒掉吸烟习惯。初步证据表明，妊娠晚期尼古丁清除率有所提高。为了评估妊娠晚期尼古丁代谢的变化，我们对从蒙特利尔四家妇产医院招募的一大群、多样化的孕妇进行了一项前瞻性队列研究。通过在妊娠24至26周及产后进行的结构化问卷调查获取吸烟史。根据每月1厘米的平均头发生长速度，将头发分段，通过免疫测定法测量每个孕期头发中尼古丁和可替宁的浓度。在所有三个孕期中，每天吸烟的平均数量与头发中的尼古丁和可替宁之间均观察到强烈的相关性。稳定吸烟者从孕早期到孕晚期，头发中的尼古丁显著减少，与此同时，头发中的可替宁显著增加。头发中尼古丁与可替宁的比例从孕早期到孕晚期显著下降。妊娠晚期尼古丁代谢增加导致全身对尼古丁的暴露减少。这种现象可能解释了为什么许多孕妇有继续吸烟的冲动，以及为什么在几项临床试验中，标准剂量的尼古丁替代疗法在减少孕期吸烟方面没有效果。
