"A randomized, double-blind, placebo-controlled trial examined the treatment efficacy of long-acting injectable naltrexone (Naltrel, DrugAbuse Sciences) for relapse prevention in 60 heroin-dependent individuals. Patients were stratified by sex and years of heroin use and randomized to receive placebo, 192 mg, or 384 mg of long-acting naltrexone intramuscular injections dosed on weeks 1 and 5. In addition to medication, patients received relapse prevention therapy and had urine monitored for drug relapse. At the end of 2 months, 39%, 60% and 68% of the placebo, 192 mg naltrexone and 384 mg naltrexone groups, respectively were still in treatment. Mean treatment drop-out occurred in 27 days, 36 days, and 48 days for the placebo, 192 mg naltrexone and 384 mg naltrexone groups. Assuming that missing urine samples were positive, patients receiving placebo had the lowest mean percentage of negative urine samples (25.3%), with the highest mean percentage of negative urine samples in the patient group receiving 384 mg of naltrexone (61.9%). There was a significant main effect of group (P = 0.03), but without assumption of missing urines being positive, was no longer significant. This study highlighted the issues of treatment retention with long-acting injectable naltrexone, but was limited by small sample size, and direct comparison to treatment retention with oral naltrexone.40"
Kjome, Kimberly L. and Moeller, F. Gerard, "Long-Acting Injectable Naltrexone for the Management of Patients with Opioid Dependence," Substance Abuse: Research and Treatment 2011:5 1–9, doi: 10.4137/SART.S5452.