The Effect of Varenicline (Chantix) and Bupropion (Zyban) on Smoking Lapse Behavior

Inclusion Criteria: * ages 18-55 * able to read and write in English * Smokers Exclusion Criteria: * any significant current medical or psychiatric conditions that would contraindicate smoking * current Diagnostic and Statistical Manual IV abuse or dependence of other substances, other than nicotine dependence or alcohol abuse * positive test result at intake appointments on urine drug screens conducted for opiates, cocaine, or benzodiazepines * women who are pregnant or nursing * suicidal, homicidal, or evidence of current severe mental illness * participants prescribed any psychotropic drug in the 30 days prior to study enrollment * blood donation within the past 6 weeks * individuals seeking treatment for smoking cessation or have attempted to quit smoking within the past 3 months * specific exclusions for bupropion administration not already specified, including: have taken monoamine inhibitors in the past 6 weeks; history of anorexia or bulimia; previous hypersensitivity to bupropion; history of alcohol or drug dependence in the past year; history of seizure disorder of any etiology * known allergy to varenicline or taking H2blockers * participation within the past 8 weeks in other studies that involve additive blood sampling and/or interventional measures that would be considered excessive in combination with the current study