[Show abstract][Hide abstract] ABSTRACT: While oral naltrexone is effective in treating alcohol and opiate dependencies, poor patient adherence and widely fluctuating plasma levels limit its efficacy. To overcome these problems, an extended-release formulation of naltrexone (Vivitrex) was developed by encapsulating naltrexone into injectable, biodegradable polymer microspheres. Pharmacokinetic studies in rats demonstrated that this formulation produced stable, pharmacologically relevant plasma levels of naltrexone for approximately 1 month following either subcutaneous or intramuscular injections. While rats receiving placebo microspheres demonstrated a pronounced analgesic response to morphine in the hot-plate test, morphine analgesia was completely blocked in rats treated with extended-release naltrexone. This antagonism began on day 1 following administration and lasted for 28 days. Rats reinjected with extended-release naltrexone 34 days after the initial dose and tested for another 35 days showed consistent suppression of morphine analgesia for an additional 28 days. mu-Opioid receptor density, as measured by [(3)H]DAMGO autoradiography, increased up to two-fold following a single injection of extended-release naltrexone. Saturation binding assays using [(3)H]DAMGO showed changes in the midbrain and striatum at 1 week after extended-release naltrexone administration, and after 1 month in the neocortex. These receptor increases persisted for 2-4 weeks after dissipation of the morphine antagonist actions of naltrexone. These data suggest that therapeutically relevant plasma levels of naltrexone can be maintained using monthly injections of an extended-release microsphere formulation, and that changes in mu-opioid receptor density do not impact its efficacy in suppressing morphine-induced analgesia in the rat. Clinical trials of extended release naltrexone for treating alcohol and opiate dependency are currently ongoing.
[Show abstract][Hide abstract] ABSTRACT: Problem: Rates of adoption of evidenced-based practices, including the use of medications, to treat opioid dependence are low and severely limit secondary prevention efforts to curtail the prescription drug epidemic.Purpose: The goal of this article was to describe how involvement in a research clinical trials network (CTN) facilitated the adoption of medications to treat opioid dependence at two community-based treatment programs (CTPs) affiliated with the Ohio Valley Node (OVN) of the National Institute on Drug Abuse's (NIDA) CTN.Key Points: Participation in a CTN may facilitate adoption by providing the infrastructure for trialability and observability, but the most critical function may be the knowledge translation that occurs through the individual-level professional relationships that develop.Conclusion: Community-based treatment providers' involvement in research networks may increase the rate of evidence-based practice (EBP) adoption and improve outcomes for patients with opioid dependence.
Progress in Community Health Partnerships Research Education and Action 01/2014; 8(1):99-107. DOI:10.1353/cpr.2014.0002
[Show abstract][Hide abstract] ABSTRACT: Impulse control disorders (ICDs) in Parkinson disease (PD) are common and can be difficult to manage. The objective of this study was to determine the efficacy and tolerability of naltrexone, an opioid antagonist, for the treatment of ICDs in PD.METHODS: Patients with PD (n = 50) and an ICD were enrolled in an 8-week, randomized (1:1), double-blind, placebo-controlled study of naltrexone 50-100 mg/d (flexible dosing). The primary outcome measure was response based on the Clinical Global Impression-Change score, and the secondary outcome measure was change in symptom severity using the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease-Rating Scale (QUIP-RS) ICD score.RESULTS: Forty-five patients (90%) completed the study. The Clinical Global Impression-Change response rate difference favoring naltrexone in completers was 19.8% (95% confidence interval [CI] -8.7% to 44.2%). While this difference was not significant (odds ratio = 1.6, 95% CI 0.5-5.2, Wald χ(2) [df] = 0.5 , p = 0.5), naltrexone treatment led to a significantly greater decrease in QUIP-RS ICD score over time compared with placebo (regression coefficient for interaction term in linear mixed-effects model = -7.37, F[df] = 4.3 [1, 49], p = 0.04). The estimated changes in QUIP-RS ICD scores from baseline to week 8 were 14.9 points (95% CI 9.9-19.9) for naltrexone and 7.5 points (95% CI 2.5-12.6) for placebo.CONCLUSIONS: Naltrexone treatment was not efficacious for the treatment of ICDs in PD using a global assessment of response, but findings using a PD-specific ICD rating scale support further evaluation of opioid antagonists for the treatment of ICD symptoms in PD.CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that in patients with PD and an ICD, naltrexone does not significantly increase the probability of achieving response. However, the study lacked the precision to exclude an important difference in response rates.
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