Research subjects will undergo a screening visit at the Massachusetts General Hospital Center for Addiction Medicine. If they meet inclusion criteria, they will be invited for the baseline visit when they will have their first MRS and will begin taking the study drug/placebo. The randomization will be done in blocks of four. The study drug/placebo is prescribed to take 2 capsules of 500 mg each, two times per day, with or without food. They will continue weekly visits for six weeks and will receive new supplies of the study drug/placebo on weeks 2 and 4. On week 6, they will have the second MRS. On weeks 8 and 16, subjects will undergo follow up visits. On several of these visits, study staff will assess for the presence of adverse events (with the UKU instrument), cigarettes use (with carbon monoxide monitoring), and abnormal involuntary movements (with the abnormal involuntary movement scale, the barnes akathisia scale, and the sympson angus scale).
