Efficacy and Tolerability of Long-Acting Injectable Formulation of Nalmefene (Nalmefene Consta 393.1 mg) for Opioid Relapse Prevention: A Multicentre, Open-Label, Randomised Controlled Trial

Abstract

Objective: To determine the efficacy and tolerability of a long-acting intramuscular formulation of Nalmefene (Nalmefene Consta 393.1 mg) for the treatment of opioid-dependent patients. Design, Setting, and Participants: A 12 weeks, open-label, randomised controlled trial conducted between June 2009-July 2011, at 14 Hospital-based drug clinics, in the 12 countries. Participants were 18 years or older, had Diagnostic and Statistical Manual of Mental Disorders-5 opioid use disorder. Of the 3200 individuals screened, 3000 (93.7%) adults were randomized 1500 participants to receive injections of Long-acting depot formulations ofNalmefene (Nalmefene Consta 393.1 mg) given intramuscularly once in 12 weeks and 1500participants to receive extended-release Naltrexone (Vivitrol 380 mg), administered intramuscularly every fourth week for 12 weeks. Main Outcomes and Measures: The primary endpoints (protocol) were: Confirmed Opioid abstinence (percentage i.e. the number of patients who achieved complete abstinence during week 12). Confirmed abstinence or “opioid-free” was defined as a negative urine drug test for opioids and no self-reported opioid use. Weeks 1 - 4 were omitted from this endpoint to allow for stabilization of abstinence. Secondary end points included a number of days in treatment, treatment retention and craving. The study also investigated, on 275 participants, degree and time course of mu-opioid receptor occupancy following single doses of Nalmefene extended-release injection (Nalmefene Consta 393.1 mg) as well as the plasma concentration of Nalmefene and Nalmefene-3-O-glucuronide. Safety was assessed by adverse event reporting. Results: Of 3000 participants, mean (SD) age was 27.1 (±4.8) years and 831 (27.7%) were women. 1500 individuals were randomized to receive injections of Long-acting depot formulations of Nalmefene (Nalmefene Consta 393.1 mg) and 1500 to receive injections of extended-release Naltrexone (Vivitrol 380 mg); 2088 participants (69.6.0%) completed the trial. Primary endpoints: Confirmed Opioid Abstinence: Complete abstinence was sustained by 86% (n = 1290) of Nalmefene patients (patients treated with Nalmefene Consta 393.1 mg, long-acting depot formulations) compared with 43% (n = 645) of patients treated with extended-release Naltrexone 380 mg (Vivitrol), during weeks 5 - 12 (χ2 = 672.34, P < 0.0001). Secondary Endpoint: Craving: A statistically and clinically significant reduction in opioid craving was observed with Nalmefene (Nalmefene Consta 393.1 mg, long-acting depot formulations) vs. Naltrexone (extended-release Naltrexone, Vivitrol 380 mg) by week 4 (P =0.0048), which persisted every week through 12 (P < 0.0001). Patients given Nalmefene (Nalmefene Consta 393.1 mg, long-acting depot formulations) had a 75% decrease in craving from baseline to week 12. Patients given a Naltrexone (extended-release Naltrexone, Vivitrol 380 mg) had a 3% increase in craving from baseline to week 12 (Mean change in self-reporting craving). Secondary Endpoint: Treatment Retention: Long-acting intramuscular formulation of Nalmefene (Nalmefene Consta 393.1 mg) helped significantly more patients complete 12 weeks treatment (n = 1245, 83%) compared with extended-release Naltrexone (Vivitrol 380 mg) (n = 570, 38%) (χ2 = 635.53, P < 0.0001). Patients on long-acting intramuscular formulation of Nalmefene (Nalmefene Consta 393.1 mg) had longer treatment retention than patients on extended-release Naltrexone (Vivitrol 380 mg). Concentrations of Nalmefene and Nalmefene-3-O-Glucuronide in Plasma: Analyses were made of 275 study sample. There was no statistically significant difference for plasma nalmefene concentrations between days 2 and 84 (p = 0.416). The plasma concentration of Nalmefene were 20.3 and 28.5 ng/ml and concentrations of nalmefene-3-O-glucuronide were 2.1 and 4.1 ng/ml, respectively. Plasma levels of Nalmefene remained above 20 ng/ml for approximately 12 weeks after administration of Nalmefene, long-acting depot formulations (Nalmefene Consta 393.1 mg). PET Assessments: Very high mu-opioid receptor occupancy by Nalmefene was detected 1 day after treatments at which time point the occupancy was 100.0% after Nalmefene injection (Nalmefene Consta 393.1 mg). Nalmefene Consta 393.1 mg injection (long-acting intramuscular formulation of Nalmefene) led to a very high occupancy ofmu-opioid receptors in all brain areas examined; the thalamus, caudate nucleus, and frontal cortex. Depending on the brain area mu-opioid receptor occupancy varied between 83.0% and 85.8% 84 days after dosing. Adverse Reactions: Adverse events were similar in opioid-dependent patients treated with long-acting intramuscular formulation of Nalmefene (Nalmefene Consta 393.1 mg) vs. patients treated with extended-release Naltrexone (Vivitrol 380 mg). Conclusions and Relevance: Long-acting depot formulations of Nalmefene (Nalmefene Consta 393.1 mg) was more effective then extended-release Naltrexone (Vivitrol 380 mg) in maintaining short-term abstinence from heroin and should be considered as a treatment option for opioid-dependent individuals.