Opioid Use and Dropout in Patients Receiving Oral Naltrexone With or Without Single Administration of Injection Naltrexone

Maria A Sullivan, Adam Bisaga, Andrew Glass, Kaitlyn Mishlen, Martina Pavlicova, Kenneth M Carpenter, John J Mariani, Frances R Levin, Edward V Nunes

BACKGROUND: Adherence to oral naltrexone has been poor and can be improved somewhat with behavioral therapy. We compared behavioral naltrexone therapy (BNT) to compliance enhancement (CE) and tested efficacy of single-dose injection naltrexone (XR-NTX; 384 mg) with behavioral therapies at further improving adherence to oral naltrexone.

METHODS: A 24-week, randomized, placebo-controlled trial (n=125) compared four treatment conditions following inpatient detoxification and oral naltrexone induction: (1) BNT+XR-NTX; (2) BNT+placebo injection; (3) CE+XR-NTX; and (4) CE+placebo injection. All participants were maintained on oral naltrexone throughout the trial. Primary outcome was retention in treatment.

RESULTS: Of 89 randomized participants, 78.7% (70/89) completed 4 weeks, 58.2% (54/89) completed 8 weeks, 47.2% (42/89) completed 12 weeks, and 25.8% (23/89) completed 24 weeks. A Cox proportional hazards regression modeled time to dropout as a function of treatment condition, baseline opioid dependence severity (bags per day of heroin use), and their interaction. Interaction of conditions by baseline severity was significant (X3(2)=9.19, p=0.027). For low-severity patients (≤ 6 bags/day), retention was highest in the BNT-XR-NTX group (60% at 6 months), as hypothesized. For high-severity (>6 bags/day) patients, BNT-XR-NTX did not perform as well, due to high early attrition.

CONCLUSION: For low-severity heroin users, single-dose XR-NTX improved long-term treatment retention when combined with behavioral therapy. In higher-severity opioid-dependent patients, XR-NTX was less helpful, perhaps because, combined with oral naltrexone, it produced higher blood levels and more withdrawal discomfort. When cost considerations recommend oral naltrexone following XR-NTX, the latter should be phased in slowly.