A Cochrane review included 1 trial (n=60) for effectiveness and 17 trials (6 RCTs) for adverse events. 2 dosages of high-dose naltrexone depot injections (384 mg) significantly increased days in treatment compared to placebo (WMD 21.00, 95% CI 10.68 to 31.32, p<0.0001). High-dose compared to low-dose (192mg) significantly increased days in treatment (WMD 12.00, 95% CI 1.69 to 22.31, p=0.02). Number of patients retained in treatment did not show significant differences between groups. Side effects were significantly more frequent in naltrexone depot groups compared to placebo. In alcohol dependent samples only, adverse effects appeared to be more frequent in the low-dose naltrexone depot groups compared to placebo (RR 1.18, 95% CI 1.02 to 1.36). In the opioid dependent sample, group differences were not statistically significant. Reports on systematic assessment of side effects and adverse events were scarce.