This study is designed to evaluate the safety and effectiveness of using a combination of two different medications (extended release naltrexone and bupropion) compared to matching placebo (an inactive substance) in the treatment of methamphetamine use disorder. Participants will undergo screening, and if eligible, will receive study medications along with brief medication management for twelve weeks, with follow up visits at weeks 14 and 16. The total study duration is around 19 weeks.

In the current study, we will recruit individuals using addictive drugs (cocaine, cannabis, opioids, or methamphetamine) and non-drug use control individuals. The study participants will fill out questionnaires, consent, and donate samples (urine, saliva, nasal swab, and blood). These samples will be used to study the causes of unhealthy conditions during drug uses. Our goal is to prevent or treat the drug-associated unhealthy conditions (i.e., anxiety, memory impairment).