Cytisine for Smoking Cessation

Inclusion Criteria: * Aged 18-65 years; * Have TUD assessed by structured clinical interview for DSM-5; * Have past year AUD (active) assessed by structured clinical interview for DSM-5; * Report daily cigarette consumption in past month and expired carbon monoxide (CO) measurement ≥10ppm at screening; * Have Fagerstrom Test of Nicotine Dependence (FTND55) score ≥4; * Have motivation to quit within 30 days i.e. Contemplation Ladder56 score ≥7; * Be willing and able to comply with all study procedural and assessment demands; * Be able to provide voluntary written informed consent. Exclusion Criteria: * Report prolonged smoking abstinence in the past month preceding screening; * Be using other smoking cessation aids * Enrolled in another smoking cessation program * Be pregnant, breastfeeding, or intending to become pregnant or breastfeed; * Exhibit suicidal thoughts or behavior in the past month; * Enrolled in another study which would interfere with study procedures or represent a potential risk to the participant * Have a serious unstable psychiatric or medical condition preventing participation in the trial. This includes some forms of schizophrenia, ischemic heart disease, heart failure, arterial hypertension (systolic BP above 150; diastolic BP above 100), cerebrovascular diseases, occlusion of blood vessels, kidney and/or liver disease, hyperthyroidism, ulcer, diabetes, Chromaffin tumours of the adrenal medulla, and gastroesophageal reflux disease (GERD)