We aimed to assess the efficacy and safety of an injectable, once monthly extended-release formulation of the opioid antagonist naltrexone (XR-NTX) for treatment of patients with opioid dependence after detoxification. Two hundreds and fifty patients with opioid dependence were enrolled into the double-blind, placebo-controlled, randomized, 24-week trial. Patients aged 18 years or over who had inpatient detoxification and 7 days or more off all opioids were enrolled at 13 clinical sites in Russia. We randomly assigned patients (1:1) to either 380 mg XR-NTX (n=124) or placebo (n=126). Participants also received 12 biweekly counseling sessions. The primary endpoint was the response profile for confirmed abstinence during weeks 5-24 assessed by urine drug tests and self report of non-use. Secondary endpoints were self-reported opioid- free days, opioid craving scores, number of days of retention, and relapse to physiological opioid dependence. In conclusion: XR-NTX represents a new treatment option. XR-NTX in conjunction with psychosocial treatment was more effective for treatment of opioid dependence compare to psychosocial support and placebo.