Participants undergo blood sample collection periodically. Lymphocytes are isolated and analyzed for baseline GST activity and level. Serum is analyzed to determine bilirubin levels to be used as surrogate UGT 1A1 activity. Analyses of CYP probe drugs will be performed using high performance liquid chromatography (HPLC) assays. A sensitive ELISA assay will be used for quantitative analyses. Urine samples are collected periodically and drug and metabolite levels will be analyzed.