Injectable, sustained-release naltrexone for the treatment of opioid dependence: a randomized, placebo-controlled trial

Ultra-Long-Term Delivery of Hydrophilic Drugs Using Injectable In Situ Cross-Linked Depots

Achieving ultra-long-term release of hydrophilic drugs over several months remains a significant challenge for existing long-acting injectables (LAIs). Existing platforms, such as in situ forming implants (ISFI), exhibit high burst release due to solvent efflux and microsphere-based approaches lead to rapid drug diffusion due to significant water exchange and large pores. Addressing these challenges, we have developed an injectable platform that, for the first time, achieves ultra-long-term release of hydrophilic drugs for over six months. This system employs a methacrylated ultra-low molecular weight pre-polymer (polycaprolactone) to create in situ cross-linked depots (ISCD). The ISCD's solvent-free design and dense mesh network, both attributed to the ultra-low molecular weight of the pre-polymer, effectively minimizes burst release and water influx/efflux. In vivo studies in rats demonstrate that ISCD outperforms ISFI by achieving lower burst release and prolonged drug release. We demonstrated the versatility of ISCD by showcasing ultra-long-term delivery of several hydrophilic drugs, including antiretrovirals (tenofovir alafenamide, emtricitabine, abacavir, and lamivudine), antibiotics (vancomycin and amoxicillin) and an opioid antagonist naltrexone. Additionally, ISCD achieved ultra-long-term release of the hydrophobic drug tacrolimus and enabled co-delivery of hydrophilic drug combinations encapsulated in a single depot. We also identified design parameters to tailor the polymer network, tuning drug release kinetics and ISCD degradation. Pharmacokinetic modeling predicted over six months of drug release in humans, significantly surpassing the one-month standard achievable for hydrophilic drugs with existing LAIs. The platform's biodegradability, retrievability, and biocompatibility further underscore its potential for improving treatment adherence in chronic conditions.

Empirically contrasting urine drug screening-based opioid use disorder treatment outcome definitions

BACKGROUND AND AIMS

A lack of consensus on the optimal outcome measures to assess opioid use disorder (OUD) treatment efficacy and their precise definition and computation has hampered the pooling of research data for evidence synthesis and meta-analyses. This study aimed to empirically contrast multiple clinical trial definitions of treatment success by applying them to the same dataset.

METHODS

Data analysis used a suite of functions, developed as a software package for the R language, to operationalize 61 treatment outcome definitions based on urine drug screening (UDS) results. Outcome definitions were derived from clinical trials that are among the most influential in the OUD treatment field. Outcome functions were applied to a harmonized dataset from three large-scale National Drug Abuse Treatment Clinical Trials Network (CTN) studies, which tested various medication for OUD (MOUD) options (n = 2492). Hierarchical clustering was employed to empirically contrast outcome definitions.

RESULTS

The optimal number of clusters identified was three. Cluster 1, comprising eight definitions focused on detecting opioid-positive UDS, did not include missing UDS in outcome calculations, potentially resulting in inflated rates of treatment success. Cluster 2, with the highest variability, included 10 definitions characterized by strict criteria for treatment success, relying heavily on UDS results from either a brief period or a single study visit. The 43 definitions in Cluster 3 represented a diverse range of outcomes, conceptualized as measuring abstinence, use reduction and relapse. These definitions potentially offer more balanced measures of treatment success or failure, as they avoid the extreme methodologies characteristic of Clusters 1 and 2.

CONCLUSIONS

Clinical trials using urine drug screening (UDS) for objective substance use assessment in outcome definitions should consider (1) incorporating missing UDS data in outcome computation and (2) avoiding over-reliance on UDS data confined to a short time frame or the occurrence of a single positive urine test following a period of abstinence.

Rapid Initiation of Injection Naltrexone for Opioid Use Disorder: A Stepped-Wedge Cluster Randomized Clinical Trial

Importance

Injectable extended-release (XR)-naltrexone is an effective treatment option for opioid use disorder (OUD), but the need to withdraw patients from opioid treatment prior to initiation is a barrier to implementation.

Objective

To compare the effectiveness of the standard procedure (SP) with the rapid procedure (RP) for XR-naltrexone initiation.

Design, Setting, and Participants

The Surmounting Withdrawal to Initiate Fast Treatment with Naltrexone study was an optimized stepped-wedge cluster randomized trial conducted at 6 community-based inpatient addiction treatment units. Units using the SP were randomly assigned at 14-week intervals to implement the RP. Participants admitted with OUD received the procedure the unit was delivering at the time of their admission. Participant recruitment took place between March 16, 2021, and July 18, 2022. The last visit was September 21, 2022.

Interventions

Standard procedure, based on the XR-naltrexone package insert (approximately 5-day buprenorphine taper followed by a 7- to 10-day opioid-free period and RP, defined as 1 day of buprenorphine at minimum necessary dose, 1 opioid-free day, and ascending low doses of oral naltrexone and adjunctive medications (eg, clonidine, clonazepam, antiemetics) for opioid withdrawal.

Main Outcomes and Measures

Receipt of XR-naltrexone injection prior to inpatient discharge (primary outcome). Secondary outcomes included opioid withdrawal scores and targeted safety events and serious adverse events. All analyses were intention-to-treat.

Results

A total of 415 participants with OUD were enrolled (mean [SD] age, 33.6 [8.48] years; 205 [49.4%] identified sex as male); 54 [13.0%] individuals identified as Black, 91 [21.9%] as Hispanic, 290 [69.9%] as White, and 22 [5.3%] as multiracial. Rates of successful initiation of XR-naltrexone among the RP group (141 of 225 [62.7%]) were noninferior to those of the SP group (68 of 190 [35.8%]) (odds ratio [OR], 3.60; 95% CI, 2.12-6.10). Withdrawal did not differ significantly between conditions (proportion of days with a moderate or greater maximum Clinical Opiate Withdrawal Scale score (>12) for RP vs SP: OR, 1.25; 95% CI, 0.62-2.50). Targeted safety events (RP: 12 [5.3%]; SP: 4 [2.1%]) and serious adverse events (RP: 15 [6.7%]; SP: 3 [1.6%]) were infrequent but occurred more often with RP than SP.

Conclusions and Relevance

In this trial, the RP of XR-naltrexone initiation was noninferior to the standard approach and saved time, although it required more intensive medical management and safety monitoring. The results of this trial suggest that rapid initiation could make XR-naltrexone a more viable treatment for patients with OUD.

Trial Registration

ClinicalTrials.gov Identifier: NCT04762537.

Clinical Implications of the Relationship Between Naltrexone Plasma Levels and the Subjective Effects of Heroin in Humans

BACKGROUND

Extended-release naltrexone (NTX) is an opioid antagonist approved for relapse prevention after medical withdrawal. Its therapeutic effect is dependent on the NTX plasma level, and as it decreases, patients may lack protection against relapse and overdose. Therefore, identifying the minimally effective NTX level needed to block opioid-induced subjective effects has important clinical implications.

METHODS

This secondary, individual-level analysis of data collected in a human laboratory study was conducted to evaluate the relationship between NTX levels and subjective effects of an intravenously administered 25-mg challenge dose of heroin in non-treatment-seeking participants with opioid use disorder (N = 12). Subjective ratings of drug liking using a 100-mm visual analog scale (VAS) and NTX levels were measured across 6 weeks after participants received a single injection of either extended-release NTX 192 mg (N = 6) or 384 mg (N = 6). Cubic spline mixed-effects models were used to provide 95% prediction intervals for individual changes in liking scores as a function of NTX levels.

RESULTS

Naltrexone levels above 2 ng/mL blocked nearly all VAS ratings of drug liking after intravenous heroin administration. Participants with NTX levels ≥ 2 ng/mL had minimal (≤20 mm) changes from placebo in VAS ratings of drug liking based on 95% prediction intervals. In contrast, NTX levels < 2 ng/mL were associated with greater variability in individual-level subjective responses.

CONCLUSIONS

In clinical practice, a plasma level range of 1 to 2 ng/mL is considered to be therapeutic in providing heroin blockade. The current findings suggest that a higher level (>2 ng/mL) may be needed to produce a consistent blockade.

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. Trial registrationclinicaltrials.gov Identifier: NCT01717963.

Implementing contingency management for stimulant use in opioid treatment programs: protocol of a type III hybrid effectiveness-stepped-wedge trial

BACKGROUND

Contingency management (CM) is an evidence-based intervention for stimulant use and is highly effective in combination with medication for opioid use disorder. Yet, uptake of CM in opioid treatment programs that provide medication for opioid use disorder remains low. This paradox in which CM is one of the most effective interventions, yet one of the least available, represents one of the greatest research-to-practice gaps in the addiction health services field. Multi-level implementation strategies are needed to address barriers to CM implementation at both the provider- and organization-level. This type III hybrid effectiveness-implementation trial was funded by the National Institute on Drug Abuse to evaluate whether a multi-level implementation strategy, the Science of Service Laboratory (SSL), can effectively promote CM implementation in opioid treatment programs. Specific aims will test the effectiveness of the SSL on implementation outcomes (primary aim) and patient outcomes (secondary aim), as well as test putative mediators of implementation outcomes (exploratory aim).

METHODS

Utilizing a fully powered type III hybrid effectiveness-implementation trial with a stepped wedge design, we propose to randomize a cohort of 10 opioid treatment programs to receive the SSL across four steps. Each step, an additional 2-3 opioid treatment programs will receive the SSL implementation strategy, which has three core components: didactic training, performance feedback, and external facilitation. At six intervals, each of the 10 opioid treatment programs will provide de-identified electronic medical record data from all available patient charts on CM delivery and patient outcomes. Staff from each opioid treatment program will provide feedback on contextual determinants influencing implementation at three timepoints.

DISCUSSION

Between planning of this protocol and receipt of funding, the landscape for CM in the USA changed dramatically, with multiple Departments of Health launching state-wide CM initiatives. We therefore accelerated the protocol timeline and offered some cursory training resources to all sites as a preparation activity. We also began partnering with multiple Departments of Health to evaluate their rollout of CM using the measures outlined in this protocol.

TRIAL REGISTRATION

This study protocol is registered via ClinicalTrials.gov Identifier: NCT05702021. Date of registration: January 27, 2023.

Metabolic profiles associated with opioid use and opioid use disorder: a narrative review of the literature

Purpose of Review

Opioid use disorder (OUD) is a chronic, relapsing condition that is epidemic in the USA. OUD is associated with serious adverse consequences, including higher incarceration rates, impaired medical and mental health, and overdose-related fatalities. Several medications with demonstrated clinical efficacy in reducing opioid use are approved to treat OUD. However, there is evidence that medications for OUD cause metabolic impairments, which raises concerns over the long-term metabolic health of individuals recovering from OUD. Here, we summarize the scientific literature on the metabolic effects of the use of opioids, including medications for treating OUD.

Recent Findings

Our findings showed lower body weight and adiposity, and better lipid profiles in individuals with OUD. In individuals with diabetes mellitus, opioid use was associated with lower blood glucose levels. In contrast, among individuals without underlying metabolic conditions, opioids promoted insulin resistance. Treatment of OUD patients with the agonists methadone or buprenorphine caused weight gain, increased liking and intake of sugar, and impaired lipid profile and glucose metabolism, whereas treatment with the antagonist naltrexone demonstrated evidence for reduced sweet preferences.

Summary

Our findings highlighted a gap in knowledge regarding the safety of medications for OUD. Further research is needed to determine how best to reduce the risk of metabolic disorder in the treatment of OUD with opioid agonists versus antagonists.

A Case of Acute Opioid Withdrawal after Liposuction Surgery in a Patient on Extended-release Buprenorphine

BACKGROUND

The US Food and Drug Administration approved the once-monthly injectable extended-release buprenorphine product to treat moderate-to-severe opioid use disorders. The patient in our case report had a liposuction procedure and immediately started having opioid withdrawal symptoms after the procedure.

CASE DESCRIPTION

The patient is a 27-year-old African-American woman who injects drugs and has morbid obesity. She enrolled in a medications for addiction treatment program and opted to get treated with extended-release buprenorphine monthly injections. She tolerated them well for a span of 6 months. In one clinic visit, she reported opioid withdrawal symptoms and started purchasing and using sublingual buprenorphine from her acquaintances. On review of history, she underwent liposuction surgery and this triggered the opioid withdrawal symptoms. Examining her abdomen revealed surgical scars at the site of the buprenorphine injection and the residual buprenorphine depot was not palpable.A subcutaneous injection of 300-mg extended release buprenorphine was administered in the right periumbilical area in this clinic visit. The following week, she was doing well and denied any withdrawal symptoms.

DISCUSSION

This is a unique case of "iatrogenic opioid withdrawal" after a fairly common surgical procedure. The extended-release buprenorphine formulation solidifies when it comes into contact with bodily fluids forming a depot. The depot and surrounding adipose tissue may have been removed during the patient's liposuction procedure, causing an immediate drop in buprenorphine levels leading to acute opioid withdrawal.This case report highlights the precautions that need to be taken before patients go for a surgical procedure like liposuction.

Noninvasive Vagal Nerve Stimulation for Opioid Use Disorder

Background

Opioid Use Disorder (OUD) is an escalating public health problem with over 100,000 drug overdose-related deaths last year most of them related to opioid overdose, yet treatment options remain limited. Non-invasive Vagal Nerve Stimulation (nVNS) can be delivered via the ear or the neck and is a non-medication alternative to treatment of opioid withdrawal and OUD with potentially widespread applications.

Methods

This paper reviews the neurobiology of opioid withdrawal and OUD and the emerging literature of nVNS for the application of OUD. Literature databases for Pubmed, Psychinfo, and Medline were queried for these topics for 1982-present.

Results

Opioid withdrawal in the context of OUD is associated with activation of peripheral sympathetic and inflammatory systems as well as alterations in central brain regions including anterior cingulate, basal ganglia, and amygdala. NVNS has the potential to reduce sympathetic and inflammatory activation and counter the effects of opioid withdrawal in initial pilot studies. Preliminary studies show that it is potentially effective at acting through sympathetic pathways to reduce the effects of opioid withdrawal, in addition to reducing pain and distress.

Conclusions

NVNS shows promise as a non-medication approach to OUD, both in terms of its known effect on neurobiology as well as pilot data showing a reduction in withdrawal symptoms as well as physiological manifestations of opioid withdrawal.

Personal recovery among people with opioid use disorder during treatment with extended-release naltrexone

Background and aims

Recovery from substance use disorders (SUD) has traditionally been equated with abstinence. "Personal recovery" however emphasizes recovery as a unique and personal process, supported by changes in connectedness, hope, identity, meaning and empowerment. This study aimed to examine personal recovery in people receiving extended-release naltrexone (XR-NTX); specifically investigate changes in personal recovery during treatment, identify groups of participants following distinct trajectories of recovery, and characteristics predicting group-belonging.

Methods

Overall change in recovery (Questionnaire about the Process of Recovery, QPR) score was assessed by linear mixed model in a subsample of 135 people with opioid use disorder (OUD) participating in a 24 + 28-week trial of XR-NTX. Growth mixture model was used to identify potential groups of people following distinct trajectories of personal recovery.

Results

Overall, there was a significant change in QPR score during treatment. Four groups with distinct recovery trajectories were identified: "initially low- increase" (G1), "initially average- no change" (G2), "initially high- no change" (G3) and "initially high- increase" (G4). The groups were different with regards to level of psychological distress, social support, and the use of benzodiazepines. In addition, previous participation in opioid agonist treatment programs, current pain, life satisfaction, employment, heroin craving and previous use of heroin also differed between groups.

Conclusions

Personal recovery among people receiving XR-NTX follows different trajectories, and various factors are associated with personal recovery. Particular attention regarding psychological distress, social support and heroin use among patients commencing XR-NTX treatment is important to facilitate successful recovery trajectories.

Surmounting Withdrawal to Initiate Fast Treatment with Naltrexone (SWIFT): A stepped wedge hybrid type 1 effectiveness-implementation study

BACKGROUND

Extended-release injectable naltrexone (XR-NTX) is an effective treatment for opioid use disorder (OUD), but initiation remains a barrier to implementation. Standard practice requires a 10- to 15-day inpatient admission prior to XR-NTX initiation and involves a methadone or buprenorphine taper followed by a 7- to 10-day washout, as recommended in the Prescribing Information for XR-NTX. A 5- to 7-day rapid induction approach was developed that utilizes low-dose oral naltrexone and non-opioid medications.

METHODS

The CTN-0097 Surmounting Withdrawal to Initiate Fast Treatment with Naltrexone (SWIFT) study was a hybrid type I effectiveness-implementation trial that compared the effectiveness of the standard procedure (SP) to the rapid procedure (RP) for XR-NTX initiation across six community inpatient addiction treatment units, and evaluated the implementation process. Sites were randomized to RP every 14 weeks in an optimized stepped wedge design. Participants (target recruitment = 450) received the procedure (SP or RP) that the site was implementing at time of admission. The hypothesis was RP will be non-inferior to SP on proportion of inpatients who receive XR-NTX, with a shorter admission time for RP. Superiority testing of RP was planned if the null hypothesis of inferiority of RP to SP was rejected.

DISCUSSION

If RP for XR-NTX initiation is shown to be effective, the shorter inpatient stay could make XR-NTX more feasible and have an important public health impact expanding access to OUD pharmacotherapy. Further, a better understanding of facilitators and barriers to RP implementation can help with future translatability and uptake to other community programs.

TRIAL REGISTRATION

NCT04762537 Registered February 21, 2021.

The role of opioid receptors in modulating Alzheimer's Disease

Alzheimer's disease (AD) is a complex neurological disorder characterized by accumulation of amyloid plaques and neurofibrillary tangles. Long term investigation of AD pathogenesis suggests that β-site amyloid precursor protein [APP] cleaving enzyme 1 (BACE1) and γ-secretase enzymes promote the amyloidogenic pathway and produce toxic Aβ peptides that are predisposed to aggregate in the brain. Hence, the targeted inhibition of BACE1/γ-secretase expression and function is a promising approach for AD therapy. Several reports have suggested that the opioid family of G-protein coupled receptors modulate the etiology of AD progression. It has also been found that changes in the signaling pathways of opioid receptors increased the expression of BACE1 and γ-secretase, and is strongly correlated with abnormal production of Aβ and pathogenesis of AD. Thus, the opioid receptor family is a promising candidate for targeted drug development to treat AD. In this review, we outline the involvement and mechanisms of opioid receptor signaling modulation in Alzheimer's Disease progression.

Medications for opioid use disorder during incarceration and post-release outcomes

BACKGROUND

Continuation or initiation of MOUDs during incarceration could improve post-release outcomes by preventing return to opioid use and reducing risk of overdose. People with OUD involved in the criminal legal system are a vulnerable population, yet little research has comprehensively examined post-release outcomes associated with receiving MOUDs in jail and prison settings.

METHODS

The authors conducted a review of published peer-reviewed literature on post-release outcomes associated with the use of MOUDs in correctional settings to determine implications for further research and policy.

RESULTS

Results showed compelling evidence supporting the use of MOUDs for currently incarcerated populations, with almost all studies showing that MOUDs provided during incarceration increased community-based treatment engagement post-release. There is also evidence that initiating or continuing MOUDs during incarceration is associated with decreased opioid use and overdoses post-release, without increasing criminal involvement.

CONCLUSIONS

Findings indicate that forcing tapering and withdrawal during incarceration can have dire consequences upon release into the community. Initiating or continuing MOUDs during incarceration reduces the risk for opioid use and overdose upon release by maintaining opioid tolerance and increasing community treatment engagement.

Mechanistic modeling-guided optimization of microneedle-based skin patch for rapid transdermal delivery of naloxone for opioid overdose treatment

Naloxone, an FDA-approved opioid inhibitor, used to reverse opioid overdose complications has up till date faced challenges associated with its delivery. Limitations include the use of invasive delivery forms and the need for frequent redosing due to its short half-life. The goal of the current study was to design a transdermal rapidly dissolving polymeric microneedle (MN) patch with delivery and pharmacokinetic properties comparable to that seen with the commercially available NAL products, eliminating their delivery limitations. Patches of varying dimensions (500 µm; 100 array,800 µm; 100array, and 600 µm; 225 array) were fabricated to evaluate the effect of increasing MN length, and density (no. of needles/unit area) on drug release. Drug dose in each of these patches was 17.89 ± 0.23 mg, 17.2 ± 0.77 mg, and 17.8 ± 1.01 mg, respectively. Furthermore, the insertion efficiency of each of the MN patches was 94 ± 4.8%, 90.6 ± 1.69%, and 96 ± 1.29%, respectively. Compared to passive permeation, a reduced lag time of about 5-15 min was observed with a significant drug flux of 15.09 ± 7.68 g[Formula: see text]/cm²/h seen in the first 1 h (p < 0.05) with the array of 100 needles (500 µm long). Over 24 h, a four and ten-fold increase in permeation was seen with the longer length and larger density MN patch, respectively, when compared to the 500 µm (100 array) patch. Model simulations and analyses revealed the significance of needle base diameter and needle count in improving systemic pharmacokinetics of NAL.

Negative allosteric modulation of CB1 cannabinoid receptor signaling suppresses opioid-mediated reward

Blockade of cannabinoid type 1 (CB₁)-receptor signaling decreases the rewarding properties of many drugs of abuse and has been proposed as an anti-addiction strategy. However, psychiatric side-effects limit the clinical potential of orthosteric CB₁ antagonists. Negative allosteric modulators (NAMs) represent a novel and indirect approach to attenuate CB₁ signaling by decreasing affinity and/or efficacy of CB₁ ligands. We hypothesized that a CB₁-NAM would block opioid reward while avoiding the unwanted effects of orthosteric CB₁ antagonists. GAT358, a CB₁-NAM, failed to elicit cardinal signs of direct CB₁ activation or inactivation when administered by itself. GAT358 decreased catalepsy and hypothermia but not antinociception produced by the orthosteric CB₁ agonist CP55,940, suggesting that a CB₁-NAM blocked cardinal signs of CB₁ activation. Next, GAT358 was evaluated using in vivo assays of opioid-induced dopamine release and reward in male rodents. In the nucleus accumbens shell, a key component of the mesocorticolimbic reward pathway, morphine increased electrically-evoked dopamine efflux and this effect was blocked by a dose of GAT358 that lacked intrinsic effects on evoked dopamine efflux. Moreover, GAT358 blocked morphine-induced reward in a conditioned place preference (CPP) assay without producing reward or aversion alone. GAT358-induced blockade of morphine CPP was also occluded by GAT229, a CB₁ positive allosteric modulator (CB₁-PAM), and absent in CB₁-knockout mice. Finally, GAT358 also reduced oral oxycodone (but not water) consumption in a two-bottle choice paradigm. Our results support the therapeutic potential of CB₁-NAMs as novel drug candidates aimed at preventing opioid reward and treating opioid abuse while avoiding unwanted side-effects.

Transcutaneous cervical vagus nerve stimulation reduces behavioral and physiological manifestations of withdrawal in patients with opioid use disorder: A double-blind, randomized, sham-controlled pilot study

BACKGROUND

Opioid Use Disorder (OUD) is a serious public health problem, and the behavioral and physiological effects of opioid withdrawal can be a major impediment to recovery. Medication for OUD is currently the mainstay of treatment; however, it has limitations and alternative approaches are needed.

OBJECTIVE

The purpose of this study was to assess the effects of transcutaneous cervical vagus nerve stimulation (tcVNS) on behavioral and physiological manifestations of acute opioid withdrawal.

METHODS

Patients with OUD undergoing acute opioid withdrawal were randomly assigned to receive double blind active tcVNS (N = 10) or sham stimulation (N = 11) while watching neutral and opioid cue videos. Subjective opioid withdrawal, opioid craving, and anxiety were measured using a Visual Analogue Scale (VAS). Distress was measured using the Subjective Units of Distress Scale (SUDS), and pain was measured using the Numerical Rating Scale (NRS) for pain. Electrocardiogram signals were measured to compute heart rate. The primary outcomes of this initial phase of the clinical trial (ClinicalTrials.gov NCT04556552) were heart rate and craving.

RESULTS

tcVNS compared to sham resulted in statistically significant reductions in subjective opioid withdrawal (p = .047), pain (p = .045), and distress (p = .004). In addition, tcVNS was associated with lower heart rate compared to sham (p = .026). Craving did not significantly differ between groups (p = .11).

CONCLUSIONS

tcVNS reduces behavioral and physiological manifestations of opioid withdrawal, and should be evaluated in future studies as a possible non-pharmacologic, easily implemented approach for adjunctive OUD treatment.

Delivering transcutaneous auricular neurostimulation (tAN) to improve symptoms associated with opioid withdrawal: results from a prospective clinical trial

Background

As pharmacological treatments are the primary option for opioid use disorder, neuromodulation has recently demonstrated efficacy in managing opioid withdrawal syndrome (OWS). This study investigated the safety and effectiveness of transcutaneous auricular neurostimulation (tAN) for managing OWS.

Methods

This prospective inpatient trial included a 30-minute randomized, sham-controlled, double-blind period followed by a 5-day open-label period. Adults with physical dependence on opioids were randomized to receive active or sham tAN following abrupt opioid discontinuation. The Clinical Opiate Withdrawal Scale (COWS) was used to determine withdrawal level, and participants were required to have a baseline COWS score ≥ 13 before enrollment. The double-blind period of the study occurred during the first 30-minutes to assess the acute effects of tAN therapy compared to a sham control. Group 1 received active tAN during both the 30-minute double-blind period and the 5-day open-label period. Group 2 received passive sham tAN (no stimulation) during the double-blind period, followed by active tAN during the 5-day open-label period. The primary outcome was change in COWS from baseline to 60-minutes of active tAN (pooled across groups, accounting for 30-minute delay). Secondary outcomes included difference in change in COWS scores between groups after 30-minutes of active or sham tAN, change in COWS scores after 120-minutes of active tAN, and change in COWS scores on Days 2–5. Non-opioid comfort medications were administered during the trial.

Results

Across all thirty-one participants, the mean (SD) COWS scores relative to baseline were reduced by 7.0 (4.7) points after 60-minutes of active tAN across both groups (p < 0.0001; Cohen’s d = 2.0), demonstrating a significant and clinically meaningful reduction of 45.9%. After 30-minutes of active tAN (Group 1) or sham tAN (Group 2), the active tAN group demonstrated a significantly greater COWS score reduction than the sham tAN group (41.7% vs. 24.1%; p = 0.036). Participants across both groups achieved an average COWS reduction up to 74.7% on Days 2–5.

Conclusion

Results demonstrate tAN is a safe and effective non-opioid approach for reducing symptoms of OWS. This study supported an FDA clearance.

Clinical trial registration

clinicaltrials.gov/ct2/show/NCT04075214, Identifier: NCT04075214, Release Date: August 28, 2019.

How access to addictive drugs affects the supply of substance abuse treatment: Evidence from Medicare Part D

This paper documents how substance abuse treatment (SAT) providers and services respond to increases in population-level opioid addiction. I do this by exploiting the implementation of Medicare Part D as an exogenous increase in the availability of prescription opioids. Starting in 2006, states with higher shares of the population eligible for Medicare Part D experienced increases in residential and hospital inpatient SAT facilities, beds dedicated to SAT, and SAT facilities offering medication-assisted treatment, relative to states with lower shares. These results suggest that the supply of SAT in the United States is capable of responding significantly to changes in demand.

Patients' experiences of continued treatment with extended-release naltrexone: a Norwegian qualitative study

BACKGROUND

The opioid antagonist extended-release naltrexone (XR-NTX) in the treatment of opioid use disorder (OUD) is effective in terms of safety, abstinence from opioid use and retention in treatment. However, it is unclear how patients experience and adjust to losing the possibility of achieving an opioid effect. This qualitative study is the first to explore how people with opioid dependence experience XR-NTX treatment, focusing on the process of treatment over time.

METHODS

Using a purposive sampling strategy, semi-structured interviews were undertaken with 19 persons with opioid use disorder (15 men, four women, 22-55 years of age) participating in a clinical trial of XR-NTX in Norway. The interviewees had received at least three XR-NTX injections. Qualitative content analysis with an inductive approach was used.

FINDINGS

Participants described that XR-NTX treatment had many advantages. However they still faced multiple challenges, some of which they were not prepared for. Having to find a new foothold and adapt to no longer gaining an effect from opioids due to the antagonist medication was challenging. This was especially true for those struggling emotionally and transitioning into the harmful use of non-opioid substances. Additional support was considered crucial. Even so, the treatment led to an opportunity to participate in society and reclaim identity. Participants had strong goals for the future and described that XR-NTX enabled a more meaningful life. Expectations of a better life could however turn into broken hopes. Although participants were largely optimistic about the future, thinking about the end of treatment could cause apprehension.

CONCLUSIONS

XR-NTX treatment offers freedom from opioids and can facilitate the recovery process for people with OUD. However, our findings also highlight several challenges associated with XR-NTX treatment, emphasizing the importance of monitoring emotional difficulties and increase of non-opioid substances during treatment. As opioid abstinence in itself does not necessarily equal recovery, our findings underscore the importance of seeing XR-NTX as part of a comprehensive, individualized treatment approach.

TRIAL REGISTRATION

Clinicaltrials.gov # NCT03647774, first Registered: Aug 28, 2018.

Sustained drug delivery strategies for treatment of common substance use disorders: Promises and challenges

Substance use disorders (SUDs) are a leading cause of death and other ill health effects in the United States and other countries in the world. Several approaches ranging from detoxification, behavioral therapy, and the use of antagonists or drugs with counter effects are currently being applied for its management. Amongst these, drug therapy is the mainstay for some drug abuse incidences, as is in place specifically for opioid abuse or alcohol dependence. The severity of the havocs observed with the SUDs has triggered constant interest in the discovery and development of novel medications as well as suitable or most appropriate methods for the delivery of these agents. The chronic need of such drugs in users warrants the need for their prolonged or sustained systemic availability. Further, the need to improve patient tolerance to medication, limit invasive drug use and overall treatment outcome are pertinent considerations for embracing sustained release designs for medications used in managing SUDs. This review aims to provide an overview on up-to-date advances made with regards to sustained delivery systems for the drugs for treatment of different types of SUDs such as opioid, alcohol, tobacco, cocaine, and cannabis use disorders. The clinical relevance, promises and the limitations of deployed sustained release approaches along with future opportunities are discussed.

Relative effectiveness of medications for opioid-related disorders: A systematic review and network meta-analysis of randomized controlled trials

INTRODUCTION

Several pharmacotherapeutic interventions are available for maintenance treatment for opioid-related disorders. However, previous meta-analyses have been limited to pairwise comparisons of these interventions, and their efficacy relative to all others remains unclear. Our objective was to unify findings from different healthcare practices and generate evidence to strengthen clinical treatment protocols for the most widely prescribed medications for opioid-use disorders.

METHODS

We searched Medline, EMBASE, PsycINFO, CENTRAL, and ClinicalTrials.gov for all relevant randomized controlled trials (RCT) from database inception to February 12, 2022. Primary outcome was treatment retention, and secondary outcome was opioid use measured by urinalysis. We calculated risk ratios (RR) and 95% credible interval (CrI) using Bayesian network meta-analysis (NMA) for available evidence. We assessed the credibility of the NMA using the Confidence in Network Meta-Analysis tool.

RESULTS

Seventy-nine RCTs met the inclusion criteria. Due to heterogeneity in measuring opioid use and reporting format between studies, we conducted NMA only for treatment retention. Methadone was the highest ranked intervention (Surface Under the Cumulative Ranking [SUCRA] = 0.901) in the network with control being the lowest (SUCRA = 0.000). Methadone was superior to buprenorphine for treatment retention (RR = 1.22; 95% CrI = 1.06-1.40) and buprenorphine superior to naltrexone (RR = 1.39; 95% CrI = 1.10-1.80). However, due to a limited number of high-quality trials, confidence in the network estimates of other treatment pairs involving naltrexone and slow-release oral morphine (SROM) remains low.

CONCLUSION

All treatments had higher retention than the non-pharmacotherapeutic control group. However, additional high-quality RCTs are needed to estimate more accurately the extent of efficacy of naltrexone and SROM relative to other medications. For pharmacotherapies with established efficacy profiles, assessment of their long-term comparative effectiveness may be warranted.

TRIAL REGISTRATION

This systematic review has been registered with PROSPERO (https://www.crd.york.ac.uk/prospero) (identifier CRD42021256212).

Comparison of naltrexone implant and oral buprenorphine-naloxone in the treatment of opiate use disorder

OBJECTIVE

We aimed to compare the effectiveness of extended-release naltrexone (XR-NTX) implant and sublingual buprenorphine-naloxone (BUP-NX) in relapse prevention in opiate use disorder (OUD).

METHODS

Medical records of 400 patients who were treated for OUD between 2016 and 2020 were retrospectively evaluated concerning sociodemographic and clinical characteristics and abstinence duration with either BUP-NX (192 patients) or XR-NTX (208 patients) as maintenance treatments.

RESULTS

The median age of patients using BUP-NX was 25.00, and the median age of patients using XR-NTX was 25.50 (p = .785). The ratio of female patients in the BUP-NX group and the XR-NTX group was 7.3% (n = 14) and 6.7% (n = 14), respectively. A significantly higher abstinence time was observed in the BUP-NX group (median = 4 months) than in the XR-NTX group (median = 3 months) (p = .015). Liver function tests were within the normal ranges at the three time points, which were just before the beginning and in the first and third months of treatment.

CONCLUSIONS

These findings suggest that BUP-NX might be more effective than XR-NTX in preventing relapse in OUD and both drugs are safe for the liver. Prospective randomized studies are needed to replicate our results.

The Role of Primary Care in the Initiation of Opioid Use Disorder Treatment in Statewide Public and Private Insurance

OBJECTIVE

To determine if individuals newly diagnosed with opioid use disorder (OUD) who saw a primary care provider (PCP) before or on the date of diagnosis had higher rates of medication treatment for OUD (MOUD).

METHODS

Observational study using logistic regression with claims data from Medicaid and a large private insurer in North Carolina from January 2014 to July 2017.

KEY RESULTS

Between 2014 and 2017, the prevalence of diagnosed OUD increased by 47% among Medicaid enrollees and by 76% among the privately insured. Over the same time period, the percent of people with an OUD who received MOUD fell among both groups, while PCP involvement in treatment increased. Of Medicaid enrollees receiving buprenorphine, the percent receiving buprenorphine from a PCP increased from 32% in 2014 to 39% in 2017. Approximately 82% of people newly diagnosed with OUD had a PCP visit in the 12 months before diagnosis in Medicaid and private insurance. Those with a prior PCP visit were not more likely to receive MOUD. Seeing a PCP at diagnosis was associated with a higher probability of receiving MOUD than seeing an emergency provider but a lower probability than seeing a behavioral health specialist or other provider type.

CONCLUSIONS

People newly diagnosed with OUD had high rates of contact with PCPs before diagnosis, supporting the importance of PCPs in diagnosing OUD and connecting people to MOUD. Policies and programs to increase access to MOUD and improve PCPs' ability to connect people to evidence-based treatment are needed.

The effects of naltrexone on retention in treatment and being opioid-free in opioid-dependent people: A systematic review and meta-analysis

BACKGROUND

Opioid dependency is a chronic relapsing disorder for which different therapeutically interventions have been developed. Naltrexone is a non-selective opioid antagonist that can be utilized for maintenance therapy in opioid dependency. In this systematic review, we aimed to evaluate the effects of naltrexone on retention in treatment and being opioid-free.

METHODS

We systematically searched PubMed and EMBASE databases up to February 5, 2022, using the following keywords: "Naltrexone," "Substance abuse," "Drug abuse," "Opiate-related disorder," and "Opioid dependence." Studies that included opiate-dependent individuals who were treated with naltrexone and assessed retention in treatment or being opioid-free were included. Two authors independently used the Cochrane risk-of-bias tool for quality assessment. A random effect model in Comprehensive Meta-Analysis software was used for the conduction of the meta-analysis. We performed subgroup analysis to evaluate the effects of naltrexone types on outcomes.

RESULTS

Eighteen studies, including 2,280 participants met our inclusion criteria. The duration of treatment ranged from 21 days to 24 months. The retention in treatment with naltrexone was 63% higher than controls (odds ratio (OR): 1.64 [95% confidence interval (CI), 0.78-3.44]. The OR for being opioid-free was 1.63 (95% CI, 0.57-4.72). Injectable naltrexone was significantly effective on retention in treatment (OR 1.86; 95% CI, 1.17-2.98).

CONCLUSIONS

We found that naltrexone could be useful for retention in treatment and being opioid-free, however, the findings were not significant. Further high-quality and large-scale observational studies are recommended.

Patient Characteristics Associated with Opioid Abstinence after Participation in a Trial of Buprenorphine versus Injectable Naltrexone

Background and Objectives: Better understanding of predictors of opioid abstinence among patients with opioid use disorder (OUD) may help to inform interventions and personalize treatment plans. This analysis examined patient characteristics associated with opioid abstinence in the X:BOT (Extended-Release Naltrexone versus Buprenorphine for Opioid Treatment) trial. Methods: This post-hoc analysis examined factors associated with past-month opioid abstinence at the 36-week follow-up visit among participants in the X:BOT study. 428 participants (75% of original sample) attended the visit at 36 weeks. Logistic regression models were used to estimate the probability of opioid abstinence across various baseline sociodemographics, clinical characteristics, and treatment variables. Results: Of the 428 participants, 143 (33%) reported abstinence from non-prescribed opioids at the 36-week follow-up. Participants were more likely to be opioid abstinent if randomized to XR-NTX (compared to BUP-NX), were on XR-NTX at week 36 (compared to those off OUD pharmacotherapy), successfully inducted onto either study medication, had longer time on study medication, reported a greater number of abstinent weeks, or had longer time to relapse during the 24-week treatment trial. Participants were less likely to be abstinent if Hispanic, had a severe baseline Hamilton Depression Rating (HAM-D) score, or had baseline sedative use. Conclusions: A substantial proportion of participants was available at follow-up (75%), was on OUD pharmacotherapy (53%), and reported past-month opioid abstinence (33%) at 36 weeks. A minority of patients off medication for OUD reported abstinence and additional research is needed exploring patient characteristics that may be associated with successful treatment outcomes.

Naltrexone Implant for Opioid Use Disorder

The continued rise in the availability of illicit opioids and opioid-related deaths in the United States has left physicians, researchers, and lawmakers desperate for solutions to this ongoing epidemic. The research into therapeutic options for the treatment of opioid use disorder (OUD) began with the introduction of methadone in the 1960s. The approval of oral naltrexone initially showed much promise, as the drug was observed to be highly potent in antagonizing the effects of opioids while producing no opioid agonist effects of its own and having a favorable side effect profile. Patients that routinely take their naltrexone reported fewer days of heroin use and had more negative drug tests than those without treatment. Poor outcomes in OUD patients treated with naltrexone have been directly tied to short treatment time. Studies have shown that naltrexone given orally vs. as an implant at the 6-month interval showed a higher non-compliance rate among those who used oral medications at the 6-month mark and a slower return to use rate. There were concerns that naltrexone could possibly worsen negative symptoms seen in opiate use disorder related to blockade of endogenous opioids that are important for pleasurable stimuli. Studies have shown that naltrexone demonstrated no increase in levels of anxiety, depression and anhedonia in participants and another study found that those treated with naltrexone had a significant reduction in mental health-related hospitalizations. The latter study also concluded that there was no increased risk for mental health-related incidents in patients taking naltrexone via a long-acting implant. Although not yet FDA approved in the United States, naltrexone implant has shown promising results in Europe and Australia and may provide a novel treatment option for opioid addiction.

Is extended release naltrexone superior to buprenorphine-naloxone to reduce drinking among outpatients receiving treatment for opioid use disorder? A secondary analysis of the CTN X:BOT trial

BACKGROUND

The comparative effectiveness of extended-release naltrexone versus buprenorphine-naloxone for opioid relapse prevention (X:BOT) trial showed that following induction, treatment with the sublingual agonist (buprenorphine-naloxone, BUP-NX) or injected antagonist (extended release naltrexone, XR-NTX) produced similar reductions in opioid relapse in injection users with opioid use disorder (OUD). Because XR-NTX reduces drinking in alcohol use disorder (AUD), we conducted a secondary analysis of the X:BOT sample of patients successfully inducted onto treatment to determine whether XR-NTX (n = 204) was superior to BUP-NX (n = 270) in reducing drinking or heavy drinking in patients with OUD.

METHODS

Standard drink units consumed were measured using the Timeline Follow-back method. Mixed-models regression was used to examine the monthly frequency of any drinking and heavy drinking over 6 months of treatment. We used a proportional hazard survival analysis to examine the time to first drink.

RESULTS

Both treatment groups reduced drinking from baseline to posttreatment (small to medium effect), but no differences between groups were detected. However, only 29% (n = 136) of the sample had AUD and 19% (n = 26/136) of those were abstinent before treatment. Analysis of a subsample enriched for possible drinking included 136 individuals with an AUD diagnosis plus 43 who did not have AUD, but reported at least one day of heavy drinking prior to the study. However, this subsample reported only 32% of days of any drinking with a median of only 13% of days designated as "heavy." Within this subsample, at baseline, the BUP-NX group reported more mean drinks per drinking day than the XR-NTX group (p = 0.03); however, there were no other significant group differences on drinking observed before, during, or at the end of treatment.

CONCLUSIONS

There was an overall reduction in drinking during treatment of OUD using both agonist and antagonist medications, so that the hypothesis that XR-NTX would be superior to BUP-NX was not supported. The study is limited by low levels of comorbid AUD or heavy drinking observed in X:BOT trial participants seeking treatment for OUD.

Naturalistic follow-up after a trial of medications for opioid use disorder: Medication status, opioid use, and relapse

AIM

This report examined naturalistic opioid use outcomes and utilization of medications for opioid use disorder (MOUD) 36 weeks post-randomization in the National Drug Abuse Treatment Clinical Trials Network (CTN) Extended-Release Naltrexone (XR-NTX) versus Buprenorphine-Naloxone (BUP-NX) for Opioid Treatment trial (CTN-0051, X:BOT).

DESIGN

X:BOT was a multisite, randomized, 24-week comparative effectiveness trial of BUP-NX (N = 287) and XR-NTX (N = 283). Study medications were discontinued following treatment completion, relapse, or dropout. Participants were encouraged to continue MOUD. This report examined opioid use outcomes in 428 (75%) of the 570 participants who attended the 36-week follow-up visit.

SETTING AND PARTICIPANTS

Adults with opioid use disorder recruited from 8 community treatment programs across the United States.

MEASUREMENTS

Outcomes included medication status (on/off MOUD), type of MOUD (BUP-NX, XR-NTX, or methadone), abstinence from non-prescribed opioids, opioid use days, relapse, and other substance use 30 days prior to the 36-week visit. Relapse was defined as opioid use for 4 consecutive weeks or 7 consecutive days in the past month. Baseline and clinical variables included opioid use severity, intravenous drug use, study medication assignment, and induction status.

FINDINGS

Of the 428 participants who completed the 36-week visit, 225 (53%) of participants were receiving MOUD and 203 (47%) were not. Compared to those off medication, participants on medication had fewer opioid use days (4.4 days (SD 9.0) versus 9.8 days (SD 12.1)), fewer met relapse criteria (37 (16.4%) versus 79 (38.9%)), and reported less stimulant use (34 (15.2%) versus 56 (27.7%)) and sedative use (14 (6.3%) versus 31 (15.3%)). There was no difference in abstinence rates between those on or off MOUD. A greater proportion of participants on XR-NTX (47 (53.4%) of 88 participants) were abstinent from non-prescribed opioids compared to those on buprenorphine (28 (23.3%) of 120 participants).

CONCLUSIONS

Naturalistic outcomes data showed that despite potential barriers to continuing treatment in the community, about half of individuals were on opioid use disorder pharmacotherapy at follow-up and those on medication generally had better outcomes. Future research should explore barriers and facilitators to treatment retention in community settings; and developing interventions tailored to improve treatment engagement and adherence.

Diversity inclusion in United States opioid pharmacological treatment trials: A systematic review

Pharmacological treatments for opioid use disorders (OUDs) may have mixed efficacy across diverse groups, i.e., sex/gender, race/ethnicity, and socioeconomic status (SES). The present systematic review aims to examine how diverse groups have been included in U.S. randomized clinical trials examining pharmacological treatments (i.e., methadone, buprenorphine, or naltrexone) for OUDs. PubMed was systematically searched according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The initial search yielded 567 articles. After exclusion of ineligible articles, 50 remained for the present review. Of the included articles, 14.0% (n = 7) reported both full (i.e., accounting for all participants) sex/gender and race/ethnicity information; only two of those articles also included information about any SES indicators. Moreover, only 22.0% (n = 11) reported full sex/gender information, and 42.0% (n = 21) reported full racial/ethnic information. Furthermore, only 10.0% (n = 5) reported that their lack of subgroup analyses or diverse samples was a limitation to their studies. Particularly underrepresented were American Indian/Alaska Native (AI/AN), Asian, Native Hawaiian/Other Pacific Islander (NH/OPI), and multiracial individuals. These results also varied by medication type; Black individuals were underrepresented in buprenorphine randomized controlled trials (RCTs) but were well represented in RCTs for methadone and/or naltrexone. In conclusion, it is critical that all people receive efficacious pharmacological care for OUDs given the ongoing opioid epidemic. Findings from the present review, however, support that participants from diverse or marginalized backgrounds are underrepresented in treatment trials, despite being at increased risk for disparities related to OUDs. Suggestions for future research are advanced. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Management of Sedation and Analgesia in Critically Ill Patients Receiving Long-Acting Naltrexone Therapy for Opioid Use Disorder

The explosion of the opioid epidemic in the United States and across the world has been met with advances in pharmacologic therapy for the treatment of opioid use disorder. Long-acting naltrexone is a promising strategy, but its use has important implications for critical care, as it may interfere with or complicate sedation and analgesia. Currently, there are two available formulations of long-acting naltrexone, which are distinguished by different administration routes and distinct pharmacokinetics. The use of long-acting naltrexone may be identified through a variety of strategies (such as physical examination, laboratory testing, and medical record review), and is key to the safe provision of sedation and analgesia during critical illness. Perioperative experience caring for patients receiving long-acting naltrexone informs management in the intensive care unit. Important lessons include the use of multimodal analgesia strategies and anticipating patients' demonstrating variable sensitivity to opioids. For the critically ill patient, however, there are important distinctions to emphasize, including changes in drug metabolism and medication interactions. By compiling and incorporating the currently available literature, we provide critical care physicians with recommendations for the sedation and analgesia for critically ill patients receiving long-acting naltrexone therapy.

Sleep moderates the relationship between stress and craving in individuals with opioid use disorder

Opioid use disorder (OUD) is a national public health concern. Craving, stress, and exposure to conditioned drug cues are implicated in risk of relapse to opioids. Although impaired sleep has been implicated in risk of relapse to other substances of misuse, little research to date has examined the relationship between sleep and craving in individuals with OUD. The present study examined sleep as a moderator of the relationship between craving and stress in a randomized controlled human laboratory study. Individuals with current OUD (N = 39) completed a 1-night hospital stay to control for factors that may affect craving, stress, and sleep. Sleep was monitored via an actigraphy watch and the Pittsburgh Sleep Quality Index. The next morning, participants were randomized to a 15-min laboratory stress task or a no-stress condition. All participants were then exposed to a 15-min opioid cue paradigm, and craving was measured via self-report. Moderation models were conducted to evaluate whether the sleep indices moderated the relationship between stress condition (independent variable) and craving (dependent variable). Average self-reported nightly sleep duration moderated the relationship between stress condition and craving for participants in the no-stress condition (b = 0.95, p < .05). Specifically, participants in the no-stress condition with lower average nightly sleep duration exhibited significantly greater craving following the opioid cue paradigm. Although preliminary, the findings add to the literature on craving, stress, and sleep among individuals with OUD. Sleep impairment may be an important target of a comprehensive, long-term treatment plan for some patients with OUD. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Enablers and hindrances for longer-term abstinence in opioid dependent individuals receiving treatment with extended-release naltrexone: A Norwegian longitudinal recovery trial (NaltRec study)

Opioid-dependence is a comprehensive, relapsing disorder with negative individual, - family, - and societal consequences. Recovery is difficult to achieve. Research has shown reduced substance use and improved health- and psychosocial factors with extended-release naltrexone (XR-NTX) treatment. Pharmacological treatment should include psychosocial interventions to improve longer-term recovery. This study explores how voluntary monthly treatment with extended-release naltrexone hydrochloride (Vivitrol®) will influence longer-term recovery, health and psychosocial relationships in opioid-dependent patients. Close relatives' experiences and societal costs will be assessed. This Norwegian naturalistic, multicenter, open-label study includes 150 opioiddependent patients. Patients are assessed every four weeks for 24 weeks, with 28 weeks optional follow-up treatment-period, and at three, six and 12 months posttreatment. Controls are opioid-dependent patients enrolled in Opioid Maintenance Treatment programs (n = 150). Data on recovery will be collected from participants, close relatives, and community health service providers. Genetic analyses of major signaling pathways and national registries on prescriptions and health care use will be analyzed. Recruitment period is September 2018 to September 2020. The assessment of medical, psychological, relational and societal factors may provide novel in-depth knowledge on the complexity of personal recovery-processes. The results are expected to have impact on priorities in treatment and follow-up for opioid dependent patients.

The changing opioid crisis: development, challenges and opportunities

The current opioid epidemic is one of the most severe public health crisis in US history. Responding to it has been difficult due to its rapidly changing nature and the severity of its associated outcomes. This review examines the origin and evolution of the crisis, the pharmacological properties of opioids, the neurobiology of opioid use and opioid use disorder (OUD), medications for opioid use disorder (MOUD), and existing and promising approaches to prevention. The results of the review indicate that the opioid epidemic is a complex, evolving phenomenon that involves neurobiological vulnerabilities and social determinants of health. Successfully addressing the epidemic will require advances in basic science, development of more acceptable and effective treatments, and implementation of public health approaches, including prevention. The advances achieved in addressing the current crisis should also serve to advance the science and treatment of other substance use disorders.

It's not just the money: The role of treatment ideology in publicly funded substance use disorder treatment

Medications for opioid use disorder (MOUD) are a first-line treatment for opioid use disorder, yet national surveys indicate that most substance use treatment facilities do not offer MOUD. This article presents the results of a qualitative analysis of interviews with leaders from 25 treatment organizations in Philadelphia, Pennsylvania, that investigated attitudes and barriers toward MOUD. Most treatment organizations that we interviewed are adopting at least one MOUD, suggesting that Philadelphia exceeds the national average of organizations with MOUD capacity. Leaders indicated that both practical resources and ideological barriers thwart adoption and implementation of MOUD in publicly funded substance use disorder treatment agencies. Organizations that had recently adopted MOUDs revealed facilitators to MOUD adoption, such as strong leadership that champions the implementation to staff and redefining recovery from substance use disorders throughout the organization. This study's findings highlight that clients, clinicians, and leadership need to address both practical and ideological barriers to expanding MOUD use.

Adapting treatment length to opioid-dependent individuals' needs and preferences: A 2-year follow-up to a 1-year study of extended-release naltrexone

BACKGROUND AND AIM

Extended-release naltrexone (XR-NTX) is an underused treatment option for opioid dependence, today only available in a few countries in the world. Although effective, safe and feasible in short-term treatment, long-term data are scarce and there is no recommendation for required treatment length. The aims of the study were to determine the perceived need of long-term XR-NTX treatment and to examine long-term treatment outcomes.

DESIGN

In this prospective cohort study, following a parent 1-year study of XR-NTX, participants received treatment with XR-NTX at their own discretion for a maximum of 104 weeks.

SETTING

Five urban, outpatient addiction clinics in Norway.

PARTICIPANTS

Opioid-dependent adults 18-60 years old (n=50) already participating in the parent study.

INTERVENTION

XR-NTX administrated as intra-muscular injections (380 mg) every 4 weeks.

MEASUREMENTS

Time in the study, use of opioids and other illicit substances, opioid craving, and treatment satisfaction reported every 4 weeks.

FINDINGS

Among 58 participants who completed the 1-year parent study, 50 chose to continue the treatment with XR-NTX. Median prolonged treatment time was 44.0 weeks (95% CI: 25.5-62.5), ranging from 8 to 104 weeks. Most participants (35, 70%) reported no relapse to opioid use during treatment while a subgroup (15, 30%) reported relapses to opioids during the study. Scores for mean treatment satisfaction and recommending treatment to others were very high (>9) and mean opioid craving score was very low (<1) on a scale ranging from 0 to 10.

CONCLUSIONS

Extended-release naltrexone (XR-NTX) was well tolerated in long-term treatment of opioid dependent individuals in Norway already in XR-NTX treatment. On average, the participants chose to continue treatment for almost 1 year beyond the initial 9 to 12 months of treatment. Participants reported high treatment satisfaction and 70% showed no relapse to opioids during the treatment period.

Types of Medication-Assisted Treatment for Opioid Use Disorder in Turkey: The Perceptions of Inpatients about Treatment Success

OBJECTIVE

The aim of this study was the following. When the different dynamics of agonist or antagonist treatments considered it is assumed that the eligible treatment to the individual may be maintained with high efficacy. Thus, we aimed to examine the difference between treatment methods, considering sociodemographics and positive perception for treatment success.

METHODS

The number of 136 individuals which their ages range between 19-50 and have been getting agonist (buprenorphine/naloxone) or antagonist (naltrexone) treatment because of opioid use disorder while resting in clinics have been evaluated to reveal the factors that may alter their perception about treatment and have been compared with sociodemographic variables and characteristics such as sociotropic and autonomic. Therefore, "Sociodemographic Data Evaluation Form," "Predictive Factors for The Addiction Treatment Success Scale," and "Sociotropy-Autonomy Scale" were used to assess the sociodemographic data, the perception towards factors which have been affected to the treatment and characteristics. The data of the individuals have been collected by the researcher via face-to-face interviews while patients were residential in the clinic.

RESULTS

According to results of our study, it has been detected that there are some differences in the perception of treatment success between individuals who have been getting agonist or antagonist treatments such as treatment method (p<0.05), treatment frequency (p<0.01) and parents' vital statuses (p<0.05).

CONCLUSION

At the end of the study it has been understood that medical and social benefits after the selection of eligible treatment methods which is suitable for individual's perception and characteristics have to be considered.

Continuous in-line homogenization process for scale-up production of naltrexone-loaded PLGA microparticles

Injectable, long-acting drug delivery systems provide effective drug concentrations in the blood for up to 6 months. Naltrexone-loaded poly(lactide-co-glycolide) (PLGA) microparticles were prepared using an in-line homogenization method. It allows the transition from a laboratory scale to scale-up production. This research was designed to understand how the processing parameters affect the properties of the microparticles, such as microparticle size distributions, surface and internal morphologies, drug loadings, and drug release kinetics, and thus, to control them. The in-line homogenization system was used at high flow rates for the oil- and water-phases, e.g., 100 mL/min and 400 mL/min, respectively, to continuously generate microparticles. A high molecular weight (148 kDa) PLGA at various concentrations was used to generate oil-phases with a range of viscosities and also to compare with a 64 and 79 kDa at a single, high concentration. The uniformity of the microparticles was found to be related to the viscosity of the oil-phase. As the viscosity of the oil-phase increased from 52.6 mPa∙s to 4046 mPa∙s, the span value (a measure of uniformity) increased from 1.24 to 3.1 for the microparticles generated at the homogenization speed of 2000 RPM. Increasing the PLGA concentration from 5.58% to 16.85% showed a corresponding rise in the encapsulation efficiency from 74.0% to 85.8% and drug loading (DL) from 27.4% to 31.7% for the microparticles made with the homogenization speed of 2000 RPM. These increases may be due to a faster shell formulation, enabling PLGA microparticles to entrap more naltrexone into the structure. A higher DL, however, shortened the drug release duration from 56 to 42 days. The changes in morphology of the microparticles during different phases of the in vitro release study were also studied for three types of microparticles made with different PLGA concentrations and molecular weights. As PLGA microparticles went through structural changes, the surface showed raisin-like wrinkled morphologies within the first 10 days. Then, the microparticles swelled to form smooth surfaces. The in-line approach produced PLGA microparticles with a highly reproducible size distribution, DL, and naltrexone release rate.

Evaluation of a Dual Fentanyl/Heroin Vaccine on the Antinociceptive and Reinforcing Effects of a Fentanyl/Heroin Mixture in Male and Female Rats

Opioid-targeted vaccines represent an emerging treatment strategy for opioid use disorder. To determine whether concurrent vaccination against two commonly abused opioids (fentanyl and heroin) would confer broader spectrum opioid coverage, the current study evaluated dual fentanyl/heroin conjugate vaccine effectiveness using a warm water tail-withdrawal and a fentanyl/heroin-vs-food choice procedure in male and female rats across a 105-day observation period. Vaccine administration generated titers of high-affinity antibodies to both fentanyl and heroin sufficient to decrease the antinociceptive potency of fentanyl (25-fold), heroin (4.6-fold), and a 1:27 fentanyl/heroin mixture (7.5-fold). Vaccination did not alter the antinociceptive potency of the structurally dissimilar opioid agonist methadone. For comparison, continuous treatment with a naltrexone dose (0.032 mg/kg/h) shown previously to produce clinically relevant plasma-naltrexone levels decreased the antinociceptive potency of fentanyl, heroin, and the 1:27 fentanyl/heroin mixture by approximately 20-fold. Naltrexone treatment also shifted the potency of 1:27 fentanyl/heroin mixture in a drug-vs-food choice self-administration procedure 4.3-fold. In contrast, vaccination did not attenuate 1:27 fentanyl/heroin mixture self-administration in the drug-vs-food choice procedure. These data demonstrate that a vaccine can simultaneously attenuate the thermal antinociceptive effects of two structurally dissimilar opioids. However, the vaccine did not attenuate fentanyl/heroin mixture self-administration, suggesting a greater magnitude of vaccine responsiveness is required to decrease opioid reinforcement relative to antinociception.

Effects of lorcaserin on oxycodone self-administration and subjective responses in participants with opioid use disorder

BACKGROUND

Lorcaserin, a high-affinity 5-HT_2C receptor agonist approved for treating obesity, decreased self-administration of oxycodone and cue-induced reinstatement of drug-seeking behavior in preclinical studies. The current investigation is the first clinical trial to evaluate the ability of lorcaserin to alter the reinforcing and subjective effects of oxycodone.

METHODS

In this 7-week inpatient trial, 12 non-treatment-seeking volunteers (11 males) with moderate-to-severe opioid use disorder were detoxified from opioids. In a randomized cross-over fashion, participants were first stabilized on lorcaserin (10 mg BID) or placebo (0 mg BID). Participants underwent a two-week testing period during which the reinforcing and subjective effects of intranasal oxycodone were examined in verbal choice, cue-exposure, and progressive-ratio choice sessions. The two testing weeks were identical with the exception that during the first week, active oxycodone (10 mg) was available during verbal choice (self-administration) sessions, and during the second week placebo oxycodone was available. Subsequently, participants were stabilized on the other medication condition (placebo or lorcaserin) and underwent the same testing procedures again.

RESULTS

Lorcaserin did not alter oxycodone self-administration. However, lorcaserin had a trend to increase "wanting heroin" when oxycodone was available, and to accentuate oxycodone-induced miosis.

CONCLUSION

Under the current experimental conditions, lorcaserin at a dose of 10 mg BID did not reliably decrease the abuse liability of oxycodone, even though the study was sufficiently powered (≥80 %) to detect clinically meaningful differences in the main outcome variables between the placebo and active lorcaserin condition. Future research could explore a wider dose range of lorcaserin and oxycodone.

Lorcaserin maintenance fails to attenuate heroin vs. food choice in rhesus monkeys

BACKGROUND

The current opioid crisis has reinvigorated preclinical research in the evaluation of non-opioid candidate treatments for opioid use disorder (OUD). Emerging evidence suggests 5-HT2C receptor agonists may attenuate the abuse-related effects of opioids. This study evaluated effectiveness of 7-day treatment with the clinically available 5-HT2C agonist lorcaserin (Belviq®) on heroin-vs.-food choice in rhesus monkeys. Lorcaserin effects were compared to effects produced by 7-day saline substitution and by 7-day treatment with the opioid antagonist naltrexone.

METHODS

Adult male (1) and female (6) rhesus monkeys were trained to respond under a concurrent schedule of food delivery (1 g pellets, fixed-ratio 100 schedule) and intravenous heroin injections (0-0.032 mg/kg/injection, fixed-ratio 10 schedule) during daily 2 h sessions. Heroin choice dose-effect functions were determined daily before and following 7-day saline substitution or 7-day continuous treatment with naltrexone (0.0032-0.032 mg/kg/h, IV) or lorcaserin (0.032-0.32 mg/kg/h, IV).

RESULTS

Under baseline conditions, increasing heroin doses maintained a dose-dependent increase in heroin choice. Both saline substitution and 7-day naltrexone treatment significantly attenuated heroin choice and produced a reciprocal increase in food choice. Continuous lorcaserin (0.32 mg/kg/h) treatment significantly increased heroin choice.

CONCLUSIONS

In contrast to saline substitution and naltrexone, lorcaserin treatment was ineffective to reduce heroin-vs.-food choice. These preclinical results do not support the therapeutic potential and continued evaluation of lorcaserin as a candidate OUD treatment.

Very low dose naltrexone in opioid detoxification: a double-blind, randomized clinical trial of efficacy and safety

Withdrawal syndrome is one of the initial focuses of opioid detoxification. Very low dose naltrexone (VLNTX) has been found to reduce opioid tolerance and dependence in animal and human clinical studies. The aim of this study was to determine the safety and efficacy of VLNTX during early stages of detoxification. In a multi-arm parallel, double-blind, randomized controlled trial, 63 opioid-dependent male participants referring to Imam Reza Rehabilitation Center were allocated to three equal groups using block randomization method. They received 0.125 mg, 0.250 mg of VLNTX or placebo daily for 10 days, together with the routine clonidine-based protocol. Self-reported and observer ratings of withdrawal severity and adverse events were measured on the 1st, 4th and 10th day of treatment. Runny eyes (p = 0.006), anxiety (p = 0.031) and dehydration (p = 0.014) were reduced during the whole 10 days in the 0.125 mg VLNTX-treated group compared to placebo. Only drowsiness (p = 0.043) and dysphoric mood (p < 0.001) were reduced in the 0.250 mg VLNTX-treated group. Results of 1st, 4th, and 10th-day assessment showed that most symptoms reductions were for the 0.125 mg VLNTX and the placebo group in the 1st and 4th days, respectively. On the 10th day, there was not any significant difference between 0.250 mg VLNTX-treated group and placebo group. No adverse effect was observed. In the starting days of detoxification, VLNTX can reduce the withdrawal symptoms, but the efficacy declined by passing time. Further studies are needed to test the utility of this new therapeutic approach.

Opioid use and dropout from extended-release naltrexone in a controlled trial: implications for mechanism

BACKGROUND AND AIMS

Extended-release formulations of naltrexone have emerged as effective treatment options for opioid use disorder. This post-hoc analysis examined the temporal relationship between episodes of opioid use and subsequent dropout in a placebo-controlled trial of extended-release injection naltrexone (XR-NTX) to draw inferences about the mechanism by which extended blockade of opioid receptors translates into clinical effectiveness.

DESIGN

This was a 24-week multiple-site, double-blind, randomized trial of monthly XR-NTX versus placebo injections. We analyzed time to dropout from treatment using survival analysis with an extended Cox model as a function of treatment (XR-NTX versus placebo) and with weekly urine drug test (UDT) results for opioids at each week as a time-dependent covariate.

SETTING

Thirteen addiction treatment programs in Russia, 2008-09.

PARTICIPANTS

A total of 250 adults with opioid use disorder who had completed in-patient detoxification.

INTERVENTION

XR-NTX injection or placebo injection every 4 weeks with weekly clinic visits and biweekly counseling.

MEASUREMENTS

Urine toxicology for opioids measured weekly and week of dropout from treatment.

FINDINGS

The Cox model yielded a significant interaction of time-dependent urine toxicology by treatment (P = 0.024). Among patients receiving placebo, a positive UDT in a given week increased the risk for dropout from treatment in the subsequent week [hazard ratio (HR) = 6.25; 95% confidence interval (CI) = 3.6-10.0], whereas among patients receiving XR-NTX, a positive UDT result showed no significant effect on risk for dropout (HR = 1.67; 95% CI = 0.6-4.5). The proportion of patients who completed all 24 weeks without any positive UDT result was 31% on XR-NTX compared with 20% on placebo (P = 0.051).

CONCLUSIONS

Extended-release injection naltrexone was effective at reducing the risk of dropout from opioid use disorder treatment after an episode of opioid use. Just under a third of patients (31%) on XR-NTX had no opioid-positive urine tests across the trial, but the hypothesis that this would differ from placebo (20%) was not confirmed.

A call for consensus in defining efficacy in clinical trials for opioid addiction: combined results from a systematic review and qualitative study in patients receiving pharmacological assisted therapy for opioid use disorder

Background

Given the complex nature of opioid addiction treatment and the rising number of available opioid substitution and antagonist therapies (OSAT), there is no ‘gold standard’ measure of treatment effectiveness, and each successive trial measures a different set of outcomes which reflect success in arbitrary or opportune terms. We sought to describe the variation in current outcomes employed across clinical trials for opioid addiction, as well as determine whether a discrepancy exists between the treatment targets that patients consider important and how treatment effectiveness is measured in the literature.

Methods

We searched nine commonly used databases (e.g., EMBASE, MEDLINE) from inception to August 1, 2015. Outcomes used across trials were extracted and categorized according to previously established domains. To evaluate patient-reported goals of treatment, semi-structured interviews were conducted with 18 adults undergoing methadone treatment.

Results

We identified 60 trials eligible for inclusion. Once outcomes were categorized into eight broad domains (e.g., abstinence/substance abuse), we identified 21 specific outcomes with furthermore 53 subdomains and 118 measurements. Continued opioid use and treatment retention were the most commonly reported measures (46%, n = 28). The majority of patients agreed that abstinence from opioids was a primary goal in their treatment, although they also stressed goals under-reported in clinical trials.

Conclusions

There is inconsistency in the measures used to evaluate the effectiveness of OSATs. Individual and population level decision making is being guided by a standard of effect considered useful to researchers yet in direct conflict with what patients deem important.

Trial registration

PROSPERO, CRD42013006507.

Availability of Medications for the Treatment of Alcohol and Opioid Use Disorder in the USA

Despite high mortality rates due to opioid overdose and excessive alcohol consumption, medications for the treatment of alcohol and opioid use disorder have not been widely used in the USA. This paper provides an overview of the literature on the availability of alcohol and opioid used disorder medications in the specialty substance use disorder treatment system, other treatment settings and systems, and among providers with a federal waiver to prescribe buprenorphine. We also present the most current data on the availability of alcohol and opioid use disorder medications in the USA. These estimates show steady growth in availability of opioid use disorder medications over the past decade and a decline in availability of alcohol use disorder medications. However, overall use of medications in the USA remains low. In 2017, only 16.3% of specialty treatment programs offered any single medication for alcohol use disorder treatment and 35.5% offered any single medication for opioid use disorder treatment. Availability of buprenorphine-waivered providers has increased significantly since 2002. However, geographic disparities in access to buprenorphine remain. Some of the most promising strategies to increase availability of alcohol and opioid use disorder medications include the following: incorporating substance use disorder training in healthcare education programs, educating the substance use disorder workforce about the benefits of medication treatment, reducing stigma surrounding the use of medications, implementing medications in primary care settings, implementing integrated care models, revising regulations on methadone and buprenorphine, improving health insurance coverage of medications, and developing novel medications for the treatment of substance use disorder.

Comparison of Rural vs Urban Direct-to-Physician Commercial Promotion of Medications for Treating Opioid Use Disorder

IMPORTANCE

In the United States, access to medications prescribed for opioid use disorder (OUD) is lower in rural counties than in urban counties. Considering the positive associations between direct-to-physician promotion of opiates and OUD medications and their prescribing rates, a study examining the association between pharmaceutical promotion of these medications and county-level rurality has merit.

OBJECTIVE

To assess whether rural counties received less pharmaceutical promotion of OUD medications compared with urban counties.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional county-level study used all reported direct-to-physician pharmaceutical payments from manufacturers of medications prescribed for OUD from January 1, 2014, through December 31, 2017, as well as demographic and economic data at the county level from 3140 US counties. Logistic regression was used with year and state-level fixed effects to compare rural county and urban county odds of receiving any promotion of OUD medications. A negative binomial model was used with year and state-level fixed effects to compare the mean pharmaceutical payments per physician and per population in rural vs urban counties.

MAIN OUTCOMES AND MEASURES

A binary indicator for whether physicians in a county received any promotion related to OUD medications in a year. The second outcome was the value of promotion (eg, meals), with dollar amount of payments for each county by year. Counties were separated into metropolitan, micropolitan, and rural categories using the National Center for Health Statistics Urban-Rural Classification Scheme.

RESULTS

Of 3140 US counties with 18 318 physicians to whom promotion of OUD medications was directed, 1166 (37.1%) were metropolitan (16 740 physicians [91.4%]), 641 (20.4%) were micropolitan (1049 physicians [5.7%]), and 1333 (42.5%) were rural (529 physicians [2.9%]). Compared with physicians in metropolitan counties, physicians in rural counties had reduced odds of receiving any promotion (adjusted odds ratio, 0.57; 95% CI, 0.44-0.74) and received lower payments (adjusted incidence rate ratio, 0.24; 95% CI, 0.17-0.34).

CONCLUSIONS AND RELEVANCE

The study findings suggest that promotion for OUD medications is less likely to occur in rural counties and that this difference in promotion of OUD medications may be associated with differential commercial costs and benefits of promotion in rural settings.

Responding to global stimulant use: challenges and opportunities

We did a global review to synthesise data on the prevalence, harms, and interventions for stimulant use, focusing specifically on the use of cocaine and amphetamines. Modelling estimated the effect of cocaine and amphetamine use on mortality, suicidality, and blood borne virus incidence. The estimated global prevalence of cocaine use was 0·4% and amphetamine use was 0·7%, with dependence affecting 16% of people who used cocaine and 11% of those who used amphetamine. Stimulant use was associated with elevated mortality, increased incidence of HIV and hepatitis C infection, poor mental health (suicidality, psychosis, depression, and violence), and increased risk of cardiovascular events. No effective pharmacotherapies are available that reduce stimulant use, and the available psychosocial interventions (except for contingency management) had a weak overall effect. Generic approaches can address mental health and blood borne virus infection risk if better tailored to mitigate the harms associated with stimulant use. Substantial and sustained investment is needed to develop more effective interventions to reduce stimulant use.

Effectiveness and selectivity of a heroin conjugate vaccine to attenuate heroin, 6-acetylmorphine, and morphine antinociception in rats: Comparison with naltrexone

BACKGROUND

One emerging strategy to address the opioid crisis includes opioid-targeted immunopharmacotherapies. This study compared effectiveness of a heroin-tetanus toxoid (TT) conjugate vaccine to antagonize heroin, 6-acetylmorphine (6-AM), morphine, and fentanyl antinociception in rats.

METHODS

Adult male and female Sprague Dawley rats received three doses of active or control vaccine at weeks 0, 2, and 4. Vaccine pharmacological selectivity was assessed by comparing opioid dose-effect curves in 50 °C  warm-water tail-withdrawal procedure before and after active or control heroin-TT vaccine. Route of heroin administration [subcutaneous (SC) vs. intravenous [IV)] was also examined as a determinant of vaccine effectiveness. Continuous naltrexone treatment (0.0032-0.032 mg/kg/h) effects on heroin, 6-AM, and morphine antinociceptive potency were also determined as a benchmark for minimal vaccine effectiveness.

RESULTS

The heroin-TT vaccine decreased potency of SC heroin (5-fold), IV heroin (3-fold), and IV 6-AM (3-fold) for several weeks without affecting IV morphine or SC and IV fentanyl potency. The control vaccine did not alter potency of any opioid. Naltrexone dose-dependently decreased antinociceptive potency of SC heroin, and treatment with 0.01 mg/kg/h naltrexone produced similar, approximate 8-fold decreases in potencies of SC and IV heroin, IV 6-AM, and IV morphine. The combination of naltrexone and active vaccine was more effective than naltrexone alone to antagonize SC heroin but not IV heroin.

CONCLUSIONS

The heroin-TT vaccine formulation examined is less effective, but more selective, than chronic naltrexone to attenuate heroin antinociception in rats. Furthermore, these results provide an empirical framework for future preclinical opioid vaccine research to benchmark effectiveness against naltrexone.