The study comprises an 8-week double-blind, within-subjects, crossover design of varenicline (up to 2mg per day) plus either prazosin (up to 8mg per day) (V+P) or placebo (V) with 20 heavy drinking smokers. Each medication phase is 3 weeks with a 2-week medication washout in between. Participants are asked to make a practice quit attempt for 3 days the last week of each medication phase.