Fifteen RCTs (n=1,071) were included in the review.
The quality of the studies was mixed, with SBU scores ranging from 21 to 30 and Jadad scores (where applicable) ranging from 1 to 4 (most assessed studies scored 3 or 4 on the Jadad scale).
Naltrexone versus control.
Efficacy outcomes (opioid-positive urines, craving and psychiatric symptoms) (10 RCTs).
Overall, there was no statistically significant difference in retention levels between naltrexone groups and comparison groups (SMD 0.15, 95% confidence interval, CI: -0.7, 0.36). The subgroup analysis showed that retention level was significantly better in the naltrexone groups in high retention studies (SMD 0.31, 95% CI: 0.08, 0.53), while there was no difference between groups in the low retention studies. The outcome of opioid-positive urines (10 RCTs) showed a result which favoured naltrexone (SMD 0.44, 95% CI: 0.07, 0.82). This was significant only in the subgroup of 6 trials with high retention. There was significant heterogeneity (p<0.05) for both the total and the high retention group results. For opioid abuse (6 RCTs) there was no difference between the groups, either overall (SMD 0.25, 95% CI: -0.12, 0.62) or in either of the retention subgroups, but there was evidence of significant overall heterogeneity. An analysis of variance showed that naltrexone was significantly more effective in studies with high retention levels than in studies with low retention levels for all outcomes except psychiatric symptoms.
Contingency management (3 RCTs).
The contingency management groups had significantly better outcomes than the control groups during naltrexone maintenance for retention (SMD 0.46, 95% CI: 0.18, 0.73), opioid-positive urines (SMD 0.33, 95% CI: 0.06, 0.60) and naltrexone ingestion (SMD 0.55, 95% CI: 0.21, 0.89). There was no evidence of statistical heterogeneity between the studies.
One study compared family versus individual therapy during naltrexone maintenance and found significant differences favouring family therapy for retention, opioid-positive urines, naltrexone ingestion and percentage of days abstinent.
One study compared behaviour therapy versus no behavioural therapy during naltrexone maintenance and found no significant differences between the groups for any outcome.
One study compared naltrexone plus fluoxetine with naltrexone alone and found that the combination therapy group had significantly better retention over 6 months (risk difference 0.23, 95% CI: 0.06, 0.42).
Results were also reported for the outcomes of craving, success and rearrests (single study of each). In each case a significant result favouring naltrexone was reported.