This trial will compare the effectiveness of a new drug combination to treating opioid addiction with extended release naltrexone alone. It is a double-blind, placebo-controlled study, meaning neither the participants nor the researchers will know who is receiving the new treatment or the placebo. The study will last 24 weeks, during which participants will receive six injections of either the new treatment or a placebo. The study's goal is to see if the new treatment can improve treatment retention, reduce opioid craving, and improve mood.