The purpose of this study is to examine the effect of varenicline and prazosin on smoking, drinking, and sleep among cigarette smokers who report heavy alcohol use. Varenicline is an FDA approved smoking cessation medication. Some smokers report sleep problems when taking varenicline. This study will test whether using prazosin, which is an FDA-approved blood pressure medication, in combination with varenicline reduces sleep problems that can be associated with using varenicline for smoking cessation. In addition, the study will examine the combined effects of these medications on smoking and drinking.