Study	Reason for exclusion
Brandon 2011	Short‐term (15 days) RCT, to test craving and psychological reward; cessation was not an outcome. Previously included but excluded for 2023 update
Bullen 2018	Study tested effect of e‐cigarettes as an adjunct to varenicline
Burstein 2006	RCT of tolerability and safety of varenicline in 24 elderly (≥ 65) smokers for 1 week. Not a cessation trial
Chantix 2006	Tested NRT alone or varenicline + NRT for 12 days to test safety and side effects of co‐administration. Not a cessation trial
Cui 2012	Open‐label non‐randomised pre/post study of 36 HIV+ participants; all received varenicline
Dezee 2013	RCT in which all participants were given varenicline; intervention tested was in‐person vs internet counselling
Dutra 2012	53 participants with schizophrenia given varenicline + cognitive behavioural therapy. Abstinence assessed at 12 weeks (end of treatment)
Ebbert 2009a	Open‐label, single‐arm Phase II study, for safety and efficacy of varenicline plus bupropion
Ebbert 2009b	Cohort analysis of 104 participants on varenicline + NRT and 135 participants treated prior to release of varenicline (93% used NRT)
Ebbert 2011b	Pilot study of varenicline for smokeless tobacco users. 12‐week outcome (EoT) reported, not long‐term post‐treatment. Previously included but excluded for 2023 update
Ebbert 2014	RCT in which all participants were given varenicline; the intervention being tested was bupropion vs placebo. See also Hong 2011
Evins 2014	Relapse prevention study that recruited already abstinence participants. Previously included but excluded for 2023 update
Faessel 2009	Outcomes were safety, tolerability and pharmacokinetics, not smoking cessation. Previously included but excluded for 2023 update
Fagerström 2010	431 smokeless tobacco users in Norway and Sweden, randomised to varenicline or placebo; CAR assessed at 12 and 26 weeks. Previously included but excluded for 2023 update
Falk 2014	Varenicline was used for alcohol reduction, not for smoking
Fatemi 2013	3‐arm RCT of varenicline, bupropion and placebo; only assessed to end of treatment (12 weeks).
Ferketich 2012	Pilot study of varenicline vs NRT; participants could choose their treatment; intervention being tested was the addition of a lung cancer screening programme
Ferketich 2013	Safety of varenicline among smokers enrolled in the Lung HIV study. Participants could choose varenicline or NRT, and were only followed for 3 months.
Fertig 2015	Study testing effect of varenicline on alcohol dependence
Frye 2013	Participants followed only until EoT (12 weeks)
Fucito 2011	Primary outcome was effects on drinking behaviour. Smoking status only measured at end of study (8 weeks)
Garza 2011	110 abstinent smokers treated with varenicline or placebo, to assess incidence and severity of neuropsychiatric symptoms; not a cessation trial. Previously included but excluded for 2023 update
Granatowicz 1976	No control group
Gray 2012	Pilot study of varenicline vs bupropion in older adolescents; outcome was reduction rather than cessation, and participants were only followed for 3 months.
Hajek 2011	101 smokers randomised to preloaded varenicline or placebo; abstinence not measured beyond 12 weeks
Hajek 2013	All were given varenicline, with the intervention tested being the addition of a NRT patch. Only followed to 3 months
Hajek 2015	Follow‐up under 6 months. Previously included but excluded for 2023 update
Hartwell 2014	Varenicline for drinking and smoking; smoking topography and pharmacogenetics rather than smoking cessation
Hawk 2012	RCT of extended pre‐TQD varenicline vs standard regimen; all participants got varenicline, and were followed only until end of treatment (12 weeks)
Hong 2011	Secondary analysis to Ebbert 2014, looking at depression in recipients of varenicline + bupropion vs varenicline alone
Hoogsteder 2014	All participants were given open‐label varenicline; the intervention being tested was the addition of NicVAX.
Hsueh 2014	Open‐label cohort study of smokers taking varenicline or NRT
Hsueh 2021	Study not randomized. Participants chose their own treatment.
Hughes 2011	218 smokers not ready to quit assigned to varenicline or placebo for 2‐8 weeks for cigarette reduction. Previously included but excluded for 2023 update
IRCT20100127003210N	Study not randomised
Jain 2014	RCT of smokeless tobacco users. Follow‐up of 12 weeks
Jennings 2014	Only followed to 16 weeks
Jiménez‐Ruiz 2013	Not an RCT
Kempe 1967	Observational uncontrolled study
Koegelenberg 2014	All participants took varenicline; the intervention being tested was the addition of NRT.
Maliszewski 1972	Uncontrolled study of 14 smokers on a 25‐day course of cytisine (Tabex); followed up for 2 weeks
Marakulin 1984	Follow‐up 6 weeks
McClure 2013	Laboratory study following an RCT of varenicline in a programmed lapse; abstinence only to 4 weeks. Previously included but excluded for 2023 update
McColl 2008	RCT of varenicline's potential as an abuse drug in smokers and non‐smokers; not a smoking cessation trial
McNaughton 2013	All participants received varenicline; the intervention being tested, as a relapse prevention aid, was interactive voice response phone calls
Meszaros 2013	Pilot study (10 participants, only 4 completers), only followed to 3 months; objective was reduction, not cessation. Previously included but excluded for 2023 update
Metelitsa 1987	Uncontrolled study
Mitchell 2012	Varenicline was for drinking reduction, not smoking cessation; only followed for 12 weeks. Previously included but excluded for 2023 update
Mocking 2013	7‐day administration of varenicline for emotional and cognitive processing in non‐smokers
Monova 2004	Follow‐up was 60 days
Nahvi 2014b	Follow‐up under 6 months
Nahvi 2020	Study tested an intervention for improving adherence to varenicline
NCT00387946	Follow‐up under 6 months
NCT00502216	Study of varenicline and naltrexone for tolerability and weight gain in smokers, not cessation
NCT00554840	Follow‐up under 6 months
NCT00828113	Relapse prevention study that recruited already abstinent participants. Previously included but excluded for 2023 update
NCT01093937	Follow‐up under 6 months
NCT01413516	Follow‐up under 6 months
NCT01532232	Study terminated
NCT01574703	Tobacco abstinence not measured
NCT01592695	Different levels of behavioural support between study arms
NCT01639560	Follow‐up under 6 months
NCT01771627	Follow‐up under 6 months
NCT01772641	Follow‐up under 6 months
NCT01806779	All participants got varenicline; the addition of bupropion was the intervention being tested.
NCT01892813	Different levels of behavioural support between study arms
NCT02048917	Follow‐up under 6 months
NCT02147132	Cross‐over trial
NCT02271919	Follow‐up under 6 months
NCT02501265	Study testing the addition of bupropion to a subset of participants receiving varenicline
NCT03709823	Follow‐up under 6 months
Nides 2021	Follow‐up under 6 months
Nollen 2011	All participants received varenicline, but half received extended counselling and half a single session. Cessation only measured to 3 month end point
Ostrovskaia 1994	Uncontrolled study
Park 2011	RCT of 49 smokers with lung cancer randomised to varenicline or placebo; follow‐up only for 12 weeks to EoT
Patterson 2010	Short‐term (3‐week) study of propensity to relapse with working memory deficits after 10 days of varenicline
Paun 1968	Controlled trial of cytisine (Tabex) (366 smokers) vs placebo (239 smokers) but followed only for 8 weeks. Observational study of 230 cytisine‐users followed for 26 weeks, but no comparator group
Pfeifer 2019	Did not measure smoking cessation as an outcome
Pfizer 2006	Follow‐up under 6 months
Poling 2010	RCT of varenicline in 31 methadone‐maintained smokers; trial lasted 3 months, and reduction was an outcome of interest (only 3‐month abstinence was reported)
Ramon 2014	RCT in which all participants received varenicline; intervention being tested was the addition of NRT
Rose 2014	RCT of varenicline versus varenicline + bupropion, in smokers who had failed to quit on NRT. All got varenicline
Schlienz 2014	4 weeks treatment with varenicline; outcome was impact on behavioural economic indices, not smoking cessation
Schmidt 1974	Non‐randomised trial
Schnoll 2011	RCT of open‐label varenicline + counselling; intervention being tested was recruitment strategies, not smoking cessation
Shim 2011	60 smokers with schizophrenia randomised to varenicline or placebo for 8 weeks; assessment at end of treatment, reduction but not abstinence rates reported
Sicras‐Mainar 2010	Multicentre observational non‐randomised non‐controlled study
Smith 2013	Follow‐up under 6 months
Stapleton 2008	Non‐randomised trial
Stoyanov 1972	Observational study with no comparator group and short but unstated length of follow‐up
Swan 2010	All participants were given varenicline (treated as an included study for 2012 update)
Tonstad 2006	Relapse prevention study that recruited already abstinent participants. Previously included but excluded for 2023 update
Tønnesen 2013	Relapse prevention study that recruited already abstinent participants. Previously included but excluded for 2023 update.
Weiner 2011	Follow‐up under 6 months
Zatonski 2006	Uncontrolled observational study

CAR: Continuous Abstinence Rate; EoT: end of treatment; NRT: nicotine replacement therapy; RCT: randomised controlled trial; TQD: target quit date