Risk of relapse to non-opioid addictive substances among opioid dependent patients treated with an opioid receptor antagonist or a partial agonist: A randomized clinical trial

Background and objective First study to assess any compensatory increase in use of non-opioid illicit substances and alcohol in opioid dependent patients randomized to treatment with extended-release naltrexone (XR-NTX) or buprenorphine-naloxone (BP-NLX) and in longer term treatment with extended-release naltrexone. Method A multicenter, outpatient, open-label randomized clinical trial where patients received intramuscular extended-release naltrexone hydrochloride, 380 mg/month, or daily sublingual buprenorphine-naloxone 8–24/2–6 mg for 12 weeks, and an option to continue with extended-release naltrexone for an additional 36 week follow-up. The study was conducted at five urban addiction clinics and detoxification units in Norway between November 2012, and July 2016. Results Among the 143 patients, 106 men and 37 women, there were no significant differences between those randomized to XR-NTX or BP-NLX in the risk of first relapse to alcohol (HR 1.31; 0.68–2.53), amphetamines (HR 0.88; 0.43–1.80), benzodiazepines (HR 1.24; 0.74–2.09) or cannabis (HR 1.55; 0.83–2.89). Also in the 36-week (12–48 weeks) follow-up period we found no significant differences between patients continuing with XR-NTX compared to those switching to XR-NTX after the randomized period in risk of first relapse to any non-opioid substance. In both study periods, the mean time in the study were longer among those relapsing to non-opioid addictive substances than those who did not. There was no significant association between first relapse to illicit opioids and first relapse to non-opioid addictive substances. Conclusion There was no increase in the risk of relapse to non-opioid addictive substances neither in short term nor longer-term treatment with extended-release naltrexone.