Smoking cessation medicine analysed in pregnant women

pregnancy smoking pregnant cigarette

Study finds varenicline use is more effective than nicotine patches in helping pregnant women to quit smoking—but more research on safety is needed

A retrospective cohort study has found pregnant women using varenicline were almost three times as likely to quit smoking than those using nicotine replacement therapy (NRT) patches.

Researchers compared quitting rates between 60 women who used varenicline and 60 who used nicotine patches during the first half of pregnancy, drawing from birth records across NSW and Western Australia between 2011 and 2012 as well as PBS data.

At the time of the study, only the patch formulation of NRT (7 mg/day, 14 mg/ day, 21 mg/day and 25 mg/day) was subsidised in Australia. While patches and other formulations such as lozenges and gums were available over the counter, use of these was not able to be measured in the study.

Varenicline was available in two preparations—a commencement pack (11 × 500 µg tablets and 42 × 1 mg tablets), and a continuation pack (56 × 1 mg tablets).

More varenicline users (33.3%) quit smoking during pregnancy than nicotine patch users (13.3%) in the cohort, researchers from the Centre for Big Data Research in Health and the National Drug and Alcohol Research Centre (NDARC) at UNSW Sydney found.

The adjusted rate difference was 24.2% (95% CI: 10.2%–38.2%) and the adjusted relative risk was 2.8 (95% CI: 1.4–5.7).

This finding is consistent with studies conducted in the non-pregnant population: the majority of prior randomised controlled trials and observational cohort studies have found smokers who used varenicline were more likely to quit smoking when compared to those who used any single form of NRT.

However this latest study, which is the first of its kind, calls for further research on the safety of varenicline during pregnancy.

“This study highlights that varenicline is more effective in pregnancy than NRT patches, where NRT is currently the only smoking cessation medicine recommended for use during pregnancy,” said lead researcher Dr Alys Havard.

“Varenicline is not currently recommended for use during pregnancy because of a lack of evidence regarding its safety when used by pregnant women,” she said.

“While we have previously shown that varenicline does not increase the risk of adverse birth outcomes such as premature birth and small baby size, we still don’t know enough about rare but serious outcomes like stillbirth and birth defects.”

There is an absence of evidence from randomised controlled trials on varenicline use during pregnancy, due to the ethical issues associated with including pregnant women in clinical trials of medicines of unknown safety, the researchers pointed out.

“Further studies are needed to corroborate these results, with evidence regarding the relative benefit of varenicline and NRT during pregnancy important for informing clinical decisions for women smoking during pregnancy,” said Dr Havard.

In Australia, 10% of women smoke during pregnancy, according to 2017 statistics from the Australian Institute of Health and Welfare.

“There is a necessity for effective smoking cessation strategies for pregnant women, especially as we know that three-quarters of pregnant smokers make at least one attempt to quit, but less than one-quarter succeed,” said Dr Havard.

Limitations for the study included the small number of pregnant smokers who used either varenicline or nicotine patches.

Adherence also appeared to be “suboptimal” among the cohort, and dispensing data did not provide information about the actual use of medications.

The study was published this week in Nicotine & Tobacco Research.

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