EVIDENCE SUMMARY
Two recent multicenter, open-label RCTs, 1 in the United States and 1 in Norway, compared monthly XR-NTX with daily BUP-NX.1,2 Both studies evaluated effectiveness (defined by either the number of people who relapsed or self-reported opioid use), cravings, and safety (defined as the absence of serious adverse events such as medically complex withdrawal or fatal overdose).
The participant populations were similar in both mean age and mean age of onset of opioid use. Duration of opioid use was reported differently (total duration or years of heavy heroin or other opioid use) and couldn’t be compared directly.
Naltrexone and buprenorphine-naloxone are similarly effective
The US study enrolled 570 opioid-dependent participants in a 24-week comparative effectiveness trial.1 The 8 study sites were community treatment programs, and the participants were recruited during voluntary inpatient detoxification admissions. Some participants were randomized while on methadone or buprenorphine tapers and some after complete detoxification.
The intention-to-treat analysis included 283 patients in the XR-NTX group and 287 in the BUP-NX group. At 24 weeks, the number of participants who’d had a relapse event (self-reported use or positive urine drug test for nonstudy opioids or refusal to provide a urine sample) was 185 (65%) for XR-NTX compared with 163 (57%) for BUP-NX (odds ratio [OR] = 1.44, 95% confidence interval [CI], 1.02 to 2.01; P = .036).
The 12-week Norwegian noninferiority trial enrolled 159 participants.2 In contrast to the US study, all participants were required to complete inpatient detoxification before randomization and induction onto the study medication.
Patients on BUP-NX reported 3.6 more days of heroin use within the previous 28 days than patients in the XR-NTX group (95% CI, 1.2 to 6; P = .003). For other illicit opioids, self-reported use was 2.4 days greater in the BUP-NX group (95% CI, −0.1 to 4.9; P = .06). Retention with XR-NTX was noninferior to BUP-NX (mean days in therapy [standard deviation], 69.3 [25.9] and 63.7 [29.9]; P = .33).
Randomizing after complete detox reduces induction failures
Naltrexone, a full opioid antagonist, precipitates withdrawal when a full or partial opioid agonist is engaging the opioid receptor. For this reason, an opioid-free interval of 7 to 10 days is generally recommended before initiating naltrexone, raising the risk for relapse during the induction process.
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