Extended-Release Injectable Naltrexone (Xr-Ntx) With Intensive Psychosocial Therapy For Amphetamine-Dependent Persons Seeking Treatment: A Placebo-Controlled Trial

Objective: Explore the efficacy of extended-release injectable naltrexone (XR-NTX) for preventing relapse to amphetamine use.Method: Clinical trial of 100 amphetamine-dependent, treatment seeking patients who were randomized to 6 monthly 380 mg doses of XR-NTX or matching placebo before entering intensive outpatient after varying lengths of inpatient treatment in Reykjavik, Iceland. Weekly urine drug tests, retention, and standardized instruments assessed efficacy.Results: Of 169 approached, 100 were randomized. Although amphetamine dependence was the main reason for seeking treatment, three-quarters or more of participants had 1 or more other substance dependencies. Of 51 randomized to XR-NTX, 20 received 4 or more injections; of 49 assigned to placebo, 26 received 4 or more injections. Of the planned 2400 weekly urine drug tests, 1247 were collected (52%); 4% of these were positive for amphetamine, 8% for benzodiazepine, 7% for marijuana, 1% for cocaine, and 1% for opioid. XR-NTX had no effect on amphetamine-positive tests, retention, or other outcomes. Those providing half or more of their tests attended more weeks of treatment than those providing less than half of their tests (m = 10.76 vs 3.31; t ( 92) = 5.91, P< 0.0001), and 92 participants provided at least 1 test.Conclusions: Adding XR-NTX to the usual combination of inpatient and intensive outpatient treatment did not reduce amphetamine use. The low prevalence of substance use among collected urine