Varenicline treatment will start one week prior to the patient's target quit date at 0.5 mg/day for days 1-3, 0.5 mg twice daily for days 4-7. On the target quit date (day 8), the dose will be increased to 1 mg twice daily and maintained for day 8-week 12. Patients will receive weekly calls during the first 4 weeks and at weeks 8, 12, and 24 to inquire about medication adherence and smoking status, motivate the patient to take the medication, encourage them not to smoke, and ask about possible side effects or other issues.

Patients will be asked to reduce their smoking during the first 4 days of treatment with aim to quit on the 5th day (target quit date). Cytisine treatment will follow standard manufacturer's dosing protocol of one tablet every 2 hours through the waking day (up to 6 tablets per day) for days 1-3, one tablet every 2.5 hours (up to 5 tablets per day) for days 4-12, one tablet every 3 hours (up to 4 tablets per day) for days 13-16, one tablet every 4-5 hours (3 tablets per day) for days 17-20, and one tablet every 6 hours (2 tablets per day) for days 21-25.

191 patients will receive varenicline for 12 weeks and regular phone calls with brief counseling Tabex: 188 patients will receive cytisine for 25 days and regular phone calls with brief counseling

Proportion of patients in the varenicline and cytisine groups who self-report seven-day abstinence from tobacco.

Proportion of patients in the varenicline and cytisine groups who self-report seven-day abstinence from tobacco.