Saliva cotinine concentrations in pregnant women who smoke and use nicotine patches

Abstract

Background and aims: Due to concerns about increased exposure to nicotine, pregnant women using nicotine replacement therapy (NRT) to stop smoking are usually advised to stop using NRT if they relapse to smoking. This study investigated whether this is justified. We compared changes in saliva cotinine from baseline to 2 weeks post-target quit date pregnant smokers who relapsed to smoking and continued to use their patches having been assigned to use nicotine patches or placebo.

Design and setting: Controlled pre-post design stratified by intervention condition from the 'Study of Nicotine Patch in Pregnancy', a randomized, placebo-controlled trial.

Participants: A sample of 268 pregnant women, assigned placebo (n = 122) or nicotine (n = 146) patches, who returned for further supplies of patches and who reported any smoking in the week prior to a visit at 2 weeks after their target quit date.

Measurements: Saliva cotinine concentrations were measured at baseline and 2 weeks after participants' target quit dates. Any smoking in the previous week was assessed by self-report, validated by expired air carbon monoxide (CO).

Findings: There was no change in saliva cotinine concentrations between baseline and 2 weeks post-target quit date in saliva cotinine concentration in the nicotine patch group [ratio of geometric means = 0.94, 95% confidence interval (CI) = 0.83 to 1.07; P = 0.37, Bayes factor = 0.15]. However, there was a reduction in reported number of cigarettes smoked/day (mean difference -6, 95% CIs -7 to -5, P < 0.001) and in CO concentrations (mean difference -3.0 parts per million, 95% CIs -4.2 to -1.9, P < 0.001). These changes were not significantly different from changes in the placebo group except for cigarette consumption, which reduced more in the nicotine group (P = 0.046).

Conclusions: In women trying to stop smoking with the aid of a nicotine patch but having smoked at 2 weeks post-target quit, their nicotine concentration did not change from baseline, but they reported smoking fewer cigarettes and had lower carbon monoxide concentrations.

Keywords: Cotinine; nicotine; nicotine replacement therapy; pregnancy; smoking; smoking cessation.

Figure 1

Flow‐chart to show each planned visit in the ‘Study of Nicotine Patch in Pregnancy’ relevant to the current study

Figure 2

Graph to show interaction of nicotine patches on cotinine concentrations at 2 weeks with increasing baseline cotinine concentrations. The shaded area represents the 95% confidence intervals. As the shaded area for log cotinine > 4.5 is above 0, there is a significant interaction of nicotine patches for an increase in cotinine at 2 weeks in women with log cotinine concentrations of greater than 4.5 (back‐transformed to 90 ng/ml), compared with placebo. [Colour figure can be viewed at wileyonlinelibrary.com]