D-cycloserine (DCS) Pretreatment + CBT + Nicotine Replacement Therapy for Smoking Cessation (DCS)

The investigators will conduct a Stage 1 pilot feasibility study at McLean Hospital to develop a medication to treat nicotine dependence. In a randomized, double-blind, placebo-controlled trial, 40 nicotine-dependent participants ages 18-65 will receive cognitive behavioral therapy (CBT) and nicotine replacement therapy (NRT) over a 10- week period, with half receiving D-cycloserine (DCS) pretreatment and half receiving placebo. Participants will receive either 250 mg DCS or placebo prior to weekly CBT sessions in addition to NRT over a 10-week treatment period. The investigators also aim to determine the effects of DCS on performance on neuropsychological tests. A 10-week treatment period will be followed by follow-up assessments including neuropsychological tests at 1 and 3 months post-treatment. Primary outcomes will include smoking as measured by carbon monoxide levels and self-report measurements.