Trends in NHS prescribing of dual NRT (DNRT) and varenicline in pregnancy and effects on infants

Date of Approval: 
2016-10-24 00:00:00
Lay Summary: 
Nicotine replacement therapy (NRT) can help smokers quit. However, NRT works less well in smokers who are pregnant, potentially because during pregnancy biological changes mean that standard doses of NRT are less good at reducing withdrawal symptoms and so pregnant women may be more likely to re-start smoking. A higher dose of NRT might increase the chances of pregnant smokers quitting, which might be achieved by prescribing pregnant women dual NRT (DNRT), a patch to provide a steady background dose of nicotine, plus a fast-acting form such as chewing gum which women can use to top-up their dose to alleviate withdrawal symptoms. Varenicline is another medication that increases the chances of quitting smoking. However, although there is no evidence that it is harmful to a growing foetus, varenicline is not currently licensed for use during pregnancy. It is possible though that some women will inadvertently take varenicline before realising they are pregnant. This study will use GP medical records to investigate how many women in the UK are currently being prescribed DNRT or varenicline during pregnancy, and will investigate how frequently adverse outcomes occur in these women compared to pregnant smokers not prescribed any stop smoking medications.
Technical Summary: 
Nicotine replacement therapy (NRT) is an effective smoking cessation aid in non-pregnant smokers, but there is evidence of only borderline effectiveness during pregnancy. Low adherence to NRT during pregnancy is the most plausible reason for NRT appearing less effective; nicotine metabolism is much faster in pregnancy and thus NRT is less likely to ameliorate withdrawal symptoms and pregnant smokers are more likely to re-start smoking. Prescribing a higher dose of NRT is a potential way to improve adherence and effectiveness, which might be achieved by use of dual NRT (DNRT), a patch to provide a steady background dose, plus a fast-acting form such as chewing gum to alleviate withdrawal symptoms as they arise. Varenicline is also an effective smoking cessation therapy when used outside of pregnancy. There is currently no evidence that varenicline is teratogenic, but despite this it is not currently licensed for use during pregnancy. It is possible though that some women will inadvertently take varenicline before realising they are pregnant. This study will investigate how many women in the UK are currently being prescribed DNRT or varenicline during pregnancy, and will investigate how frequently adverse outcomes occur in these women compared to pregnant smokers who are not prescribed any stop smoking medications.
Health Outcomes to be Measured: 
For Study 1 (description of DNRT and varenicline prescribing) and Study 2 (exploration of characteristics of women prescribed DNRT and varenicline) the outcome is prescribing as described above. For Study 3 (comparison of rates of adverse outcomes) the outcome measures which will be assessed are: low birth weight (<2.5kg); preterm birth (<37 weeks gestation); mode of delivery; presence of major congenital abnormality (using the same classifications as in our previous work). We will also present figures for the mean or median (as appropriate) birthweight in kg and gestation in weeks for the different exposure groups. Initially, we will use outcome data as recorded in mothers' and children's primary care records, but for the subset of English practices with linked secondary care HES data we will explore whether outcome data recorded in HES can be used to supplement these. In addition, from HES data we will ascertain whether children were admitted to a neonatal intensive care unit (NICU) at birth and present absolute risks for this outcome.
Application Number: 
16_151
Collaborators: 

Lisa Szatkowski - Chief Investigator - University of Nottingham
Lisa Szatkowski - Corresponding Applicant - University of Nottingham
Laila Tata - Collaborator - University of Nottingham
Timothy Coleman - Collaborator - University of Nottingham

Linkages: 
CPRD Mother-Baby Link;HES Admitted Patient Care;Patient Level Index of Multiple Deprivation;Practice Level Index of Multiple Deprivation