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Does the nicotine metabolite ratio moderate smoking cessation treatment outcomes in real‐world settings? A prospective study
Author(s) -
Shahab Lion,
Bauld Linda,
McNeill Ann,
Tyndale Rachel F.
Publication year - 2019
Publication title -
addiction
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.424
H-Index - 193
eISSN - 1360-0443
pISSN - 0965-2140
DOI - 10.1111/add.14450
Subject(s) - varenicline , medicine , smoking cessation , cotinine , nicotine replacement therapy , abstinence , confidence interval , prospective cohort study , nicotine , psychiatry , pathology
Background and aims In smoking treatment trials comparing varenicline with transdermal nicotine replacement therapy (NRT), stratified by nicotine metabolite (3‐hydroxycotinine/cotinine) ratio (NMR), the relative benefit of varenicline is greater among normal rather than slow metabolizers. This study tested if the relative effectiveness of varenicline and NRT is associated with NMR status in a natural treatment setting. A secondary aim was to test if this relationship is moderated by behavioural support. Design Prospective observational multi‐centre study with 4‐week and 52‐week follow‐up. Setting Nine English Stop Smoking Services (SSS). Participants Data came from 1556 smokers (aged ≥ 16 years) attending SSS between March 2012 and March 2013. Interventions Participants received pharmacotherapy together with behavioural support. Measurements The primary outcome was carbon monoxide‐verified continuous abstinence at both follow‐up times. Main explanatory variables were (1) NMR status [slow (NMR < 0.31, n = 451) versus normal (NMR ≥ 0.31, n = 1105) metabolizers]; (2) pharmacotherapy (varenicline versus NRT) and (3) behavioural support (individual versus group‐based treatment). Analyses adjusted for baseline socio‐demographic, SSS, mental/physical health and smoking characteristics. Findings Of participants, 44.2% [95% confidence interval (CI) = 41.7–46.6%] and 8.0% (95% CI = 6.8–9.5%) were continuously abstinent at 4 and 52 weeks. Varenicline was more effective than NRT at 4 weeks ( P < 0.001) but only marginally so at 52 weeks ( P = 0.061). There was no or inclusive evidence that NMR status moderated relative efficacy of varenicline and NRT at 4‐ [ P = 0.60, Bayes factor (BF) = 0.25] or 52‐week follow‐ups ( P = 0.74, BF = 0.73). However, this relationship was moderated by behavioural support ( p = 0.012): the relative benefit of varenicline over NRT at 52‐week follow‐up was greater in slow, not normal, metabolizers receiving group rather than individual support ( P = 0.012). Conclusions In a real‐world setting, the nicotine metabolite ratio status of treatment‐seeking smokers does not appear to contribute substantially to the differential effectiveness of varenicline and nicotine replacement therapy in Stop Smoking Services, when both pharmacotherapy and behavioural support are self‐selected.