Aim: To investigate the efficacy of low doses of naltrexone in relapse prevention for heroin dependence.
Design: Double blind, randomised comparison of three groups-Group 1 taking 50mg per day, Group 2: 0.5mg per day, and Group 3: 0.05 mg per day.
Participants: Sixty-six dependent heroin users.
Interventions: After detoxification followed by 1 week on 50mg per day naltrexone, participants were randomised to trial medication. All were offered counselling and monitored with weekly clinical reviews. Research interviews were conducted at three and 6 months.
Outcome measures: Retention in treatment and heroin use at 3 and 6 months. Secondary outcome measures were side effects and craving.
Findings: Mean days retained in randomised treatment were-Group 1: 58.9 days; Group 2: 46.6 days; and Group 3: 47.8 days. Differences in retention were not significant using survival analysis. However, nine of the first 60 participants, transferred to the 50 mg dose, and one transferred to a lower dose (chi-square = 0.142; P = 0.018). At follow-up, there was no relationship between abstinence from heroin and naltrexone dose, nor between level of heroin use and dose. There were no differences between groups in craving or depression.
Conclusion: Low doses of naltrexone had no discernible advantage, and participants preferred 50mg per day. Despite preference for blocking doses of naltrexone, outcomes appeared to be independent of naltrexone dose.