Evaluation of the Safety and Effects of Psychoactive Substances in People With Past Opioid Use

The purpose of this study is to understand how kratom affects people. In this study, kratom will be compared with another substance and a placebo (an inactive substance). Researchers will also study how the substances move through and affect the body. This includes examining how the body absorbs, processes, and eliminates the drug (pharmacokinetics), as well as how the drug affects the body and how it may make you feel (pharmacodynamics). The information collected will help researchers better understand the effects and potential risks of kratom.