Varenicline alone or with nicotine e-cigarettes for smoking cessation in people with mental illness and drug and/or alcohol dependence.

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People with mental illnesses or alcohol and/or other drug addictions are a group that needs to quit smoking: smoking prevalence is high among this population. They also have a high burden of tobacco-related illness. Current cessation treatments adopt a ‘one size fits all’ approach, overlooking considerable between-person variation in response to medication: the one third of smokers who reduce the amount they smoke by at least 50% (‘responders’) during the first two weeks after starting varenicline or nicotine replacement treatment (NRT) are 2.5 times more likely to quit smoking than those who do not (‘non-responders’). Trials (total N=557) showed NRT non-responders without a dual diagnosis can experience quit rates at 6 months identical to NRT responders by switching to varenicline or adding bupropion to NRT. Combining varenicline with either bupropion or NRT increased quit rates over varenicline alone, whilst the efficacy of nicotine e-cigarettes may be enhanced when used in addition to varenicline. These approaches to treatment have neither been integrated nor trialed among people with a dual diagnosis who are varenicline non-responders (a group with great opportunity to benefit should such simple changes to the use of available treatments lead to improved cessation efficacy). Aims : To determine whether adding a nicotine e-cigarette to varenicline plus behavioural support improves 6 month smoking cessation outcomes, relative to remaining on varenicline alone plus behavioural support, in people with a dual diagnosis who are varenicline non-responders. Design: An open label, pragmatic 3 arm, randomised controlled trial with the study population adult (18 years and older) outpatients currently receiving treatment who want to stop smoking. Exclusion criteria: contra-indications to trial medications and uncontrolled dual diagnosis symptoms (assessed by case doctor). Interventions: Participants will be prescribed varenicline by their case doctor, and receive telephone behavioural support from smoking cessation specialists for 2 weeks; those reporting a reduction in baseline cigarettes smoked per day of >50% by day 14 will continue on varenicline with referral to local cessation services. Varenicline non-responders will be randomised to one of 2 treatment arms for 12 weeks: 1) varenicline + nicotine e-cigarette; 2) varenicline only. All participants will set a target quit date for 2 weeks later and receive 6 more support calls over the next 6 weeks; the primary outcome will be measured at 24 weeks after randomisation.