The purpose of this research study is to determine if the botanical product kratom changes the effects and/or breakdown of a drug of interest. This study will consist of four study arms. During Arm 1, you will be given a single low dose of kratom tea. During Arm 2, you will be given a single dose of the drug. During Arm 3, you will be given both kratom tea and the drug. During Arm 4, you will drink kratom tea daily at home for 4 days (pre-measured doses and detailed instructions on how to prepare the tea each day will be provided). You will then return to the clinical study site, where you will be given kratom tea and the drug. Your pupil diameter will be measured by the research staff at time intervals throughout the day. Blood will be drawn from an intravenous line during Arms 2, 3, and 4. Urine samples will also be collected during those arms. The inpatient days for Arms 2, 3, and 4 will be followed by an outpatient visit the following morning, when blood will be drawn and pupil diameter will be measured; you will also return your urine jug(s) at this visit. You will receive a screening medical exam and will undergo routine blood and urine laboratory tests, as well as a urine toxicology screen for common drugs of abuse prior to participating in the study.