Long-acting depot formulations of naltrexone for heroin dependence: a review

Evaluating preferences for medication formulation and treatment model among people who use opioids non-medically: A web-based cross-sectional study

INTRODUCTION

Over the past decade, treatment for opioid use disorder has expanded to include long-acting injectable and implantable formulations of medication for opioid use disorder (MOUD), and integrated treatment models systematically addressing both behavioral and physical health. Patient preference for these treatment options has been underexplored. Gathering data on OUD treatment preferences is critical to guide the development of patient-centered treatment for OUD. This cross-sectional study assessed preferences for long-acting MOUD and integrated treatment using an online survey.

METHODS

An online Qualtrics survey assessed preferences for MOUD formulation and integrated treatment models. The study recruited participants (n = 851) in October and November 2019 through advertisements or posts on Facebook, Google AdWords, Reddit, and Amazon Mechanical Turk (mTurk). Eligible participants scored a two or higher on the opioid pain reliever or heroin scales of the Tobacco, Alcohol Prescription Medication and other Substance Use (TAPS) Tool. Structured survey items obtained patient preference for MOUD formulation and treatment model. Using stated preference methods, the study assessed preference via comparison of preferred options for MOUD and treatment model.

RESULTS

In the past year, 824 (96.8 %) participants reported non-prescribed use of opioid pain relievers (mean TAPS score = 2.72, SD = 0.46) and 552 (64.9 %) reported heroin or fentanyl use (mean TAPS score = 2.73, SD = 0.51). Seventy-four percent of participants (n = 631) reported currently or previously receiving OUD treatment, with 407 (48.4 %) receiving MOUD. When asked about preferences for type of MOUD formulation, 452 (53.1 %) preferred a daily oral formulation, 115 (13.5 %) preferred an implant, 114 (13.4 %) preferred a monthly injection and 95 (11.2 %) preferred a weekly injection. Approximately 8.8 % (n = 75) would not consider MOUD regardless of formulation. The majority of participants (65.2 %, n = 555) preferred receiving treatment in a specialized substance use treatment program distinct from their medical care, compared with receiving care in an integrated model (n = 296, 34.8 %).

CONCLUSIONS

Though most participants expressed willingness to try long-acting MOUD formulations, the majority preferred short-acting formulations. Likewise, the majority preferred non-integrated treatment in specialty substance use settings. Reasons for these preferences provide insight on developing effective educational tools for patients and suggesting targets for intervention to develop a more acceptable treatment system.

Overcoming barriers to patient adherence: the case for developing innovative drug delivery systems

Poor medication adherence is a pervasive issue with considerable health and socioeconomic consequences. Although the underlying reasons are generally understood, traditional intervention strategies rooted in patient-centric education and empowerment have proved to be prohibitively complex and/or ineffective. Formulating a pharmaceutical in a drug delivery system (DDS) is a promising alternative that can directly mitigate many common impediments to adherence, including frequent dosing, adverse effects and a delayed onset of action. Existing DDSs have already positively influenced patient acceptability and improved rates of adherence across various disease and intervention types. The next generation of systems have the potential to instate an even more radical paradigm shift by, for example, permitting oral delivery of biomacromolecules, allowing for autonomous dose regulation and enabling several doses to be mimicked with a single administration. Their success, however, is contingent on their ability to address the problems that have made DDSs unsuccessful in the past.

Nanoparticle delivery systems for substance use disorder

Innovative breakthroughs in nanotechnology are having a substantial impact in healthcare, especially for brain diseases where effective therapeutic delivery systems are desperately needed. Nanoparticle delivery systems offer an unmatched ability of not only conveying a diverse array of diagnostic and therapeutic agents across complex biological barriers, but also possess the ability to transport payloads to targeted cell types over a sustained period. In substance use disorder (SUD), many therapeutic targets have been identified in preclinical studies, yet few of these findings have been translated to effective clinical treatments. The lack of success is, in part, due to the significant challenge of delivering novel therapies to the brain and specific brain cells. In this review, we evaluate the potential approaches and limitations of nanotherapeutic brain delivery systems. We also highlight the examples of promising strategies and future directions of nanocarrier-based treatments for SUD.

Time-dependent regional brain distribution of methadone and naltrexone in the treatment of opioid addiction

Opioid addiction is a serious public health concern with severe health and social implications; therefore, extensive therapeutic efforts are required to keep users drug free. The two main pharmacological interventions, in the treatment of addiction, involve management with methadone an mu (μ)-opioid agonist and treatment with naltrexone, μ-opioid, kappa (κ)-opioid and delta (δ)-opioid antagonist. MET and NAL are believed to help individuals to derive maximum benefit from treatment and undergo a full recovery. The aim of this study was to determine the localization and distribution of MET and NAL, over a 24-hour period in rodent brain, in order to investigate the differences in their respective regional brain distributions. This would provide a better understanding of the role of each individual drug in the treatment of addiction, especially NAL, whose efficacy is controversial. Tissue distribution was determined by using mass spectrometric imaging (MSI), in combination with quantification via liquid chromatography tandem mass spectrometry. MSI image analysis showed that MET was highly localized in the striatal and hippocampal regions, including the nucleus caudate, putamen and the upper cortex. NAL was distributed with high intensities in the mesocorticolimbic system including areas of the cortex, caudate putamen and ventral pallidum regions. Our results demonstrate that MET and NAL are highly localized in the brain regions with a high density of μ-receptors, the primary sites of heroin binding. These areas are strongly implicated in the development of addiction and are the major pathways that mediate brain stimulation during reward.

Management of Opioid Use Disorder Treatment: An Overview

It is important for nurses not working in the area of addictions to be informed of the diagnosis and treatment of opioid use disorder so that they may serve as a resource, educate others, and influence and refer individuals to seek treatment on the basis of best evidence. In this article, we provide an overview of the postscreening diagnosis and treatment of opioid use disorders with an emphasis on medication-assisted treatment, starting with the definition of substance use disorder, tolerance, dependence, and addiction.

Amphiphilic Block Copolymer Microspheres Derived from Castor Oil, Poly(ε-carpolactone), and Poly(ethylene glycol): Preparation, Characterization and Application in Naltrexone Drug Delivery

In the present study, the newly synthesized castor oil-derived thioether-containing ω-hydroxyacid (TEHA) block copolymers with polycaprolactone (TEHA-b-PCL), with methoxypoly(ethylene glycol) (mPEG), (TEHA-b-mPEG) and with poly(ethylene glycol) (PEG) (TEHA-b-PEG-b-TEHA), were investigated as polymeric carriers for fabrication of naltrexone (NLX)-loaded microspheres by the single emulsion solvent evaporation technique. These microspheres are appropriate for the long-term treatment of opioid/alcohol dependence. Physical properties of the obtained microspheres were characterized in terms of size, morphology, drug loading capacity, and drug release. A scanning electron microscopy study revealed that the desired NLX-loaded uniform microspheres with a mean particle size of 5⁻10 µm were obtained in all cases. The maximum percentage encapsulation efficiency was found to be about 25.9% for the microspheres obtained from the TEHA-b-PEG-b-TEHA copolymer. Differential scanning calorimetry and X-ray diffractometry analysis confirmed the drug entrapment within microspheres in the amorphous state. In vitro dissolution studies revealed that all NLX-loaded formulations had a similar drug release profile: An initial burst release after 24 h, followed by a sustained and slower drug release for up to 50 days. The analysis of the release kinetic data, which were fitted into the Korsmeyer⁻Peppas release model, indicated that diffusion is the main release mechanism of NLX from TEHA-b-PCL and TEHA-b-mPEG microspheres, while microspheres obtained from TEHA-b-PEG-b-TEHA exhibited a drug release closer to an erosion process.

A qualitative assessment of attitudes about and preferences for extended-release naltrexone, a new pharmacotherapy to treat opioid use disorders in Ukraine

Numerous individual barriers, including negative attitudes toward opioid agonist therapies (OAT), have undermined HIV prevention efforts in Ukraine where the epidemic is concentrated in people who inject drugs (PWID). The recent availability of extended-release naltrexone (XR-NTX), an opioid antagonist, provides new opportunities for treatment and prevention, but little is known about patient preferences. We conducted qualitative analysis using focus groups (FG) of PWID recruited based on OAT experience: currently, previously, and never on OAT in five Ukrainian cities. FG included 199 PWID in 25 focus groups. Focus group transcripts were coded and analyzed using a modified grounded theory approach to identify common themes and domains related to attitudes about and preferences for XR-NTX, relative to other treatments. Interest in XR-NTX was supported if supervised opioid withdrawal and psychological support were assured. Other factors supporting XR-NTX included a focus on younger PWID early in their injection career and motivated for recovery. Perceptions of recovery included not receiving psychoactive medications like methadone or buprenorphine. With more information, XR-NTX could be a viable option for PWID in Ukraine, especially if concerns regarding withdrawal and psychological support are adequately addressed.

Sustained opioid antagonism modulates striatal sensitivity to baby schema in opioid use disorder

BACKGROUND

Chronic opioid misuse is associated with reduced sensitivity to natural rewards and social motivation deficits that include impaired caregiving. The neurobiological mechanisms underlying these deficits and their response to treatment are not well understood. Baby schema (Kindchenschema) is a set of juvenile physical features, which is perceived as "cute" and triggers motivation for caregiving. Recent studies suggest that the "baby schema effect" is mediated by the brain "reward" network. We studied the impact of opioid antagonist treatment on the baby schema response in patients with opioid use disorder.

METHODS

Forty-seven (24 F) recently detoxified patients with opioid use disorder underwent functional magnetic resonance imaging (fMRI) while viewing infant portraits that were parametrically manipulated for baby schema content and rating them for cuteness, at baseline and during treatment with the injectable extended release opioid antagonist naltrexone (XRNTX). The study was not placebo-controlled.

RESULTS

The behavioral effect of baby schema, indexed by "cuteness" ratings, was present and unaffected by XRNTX. The brain response to baby schema was absent at baseline, but present in the bilateral ventral striatum after two weeks of XRNTX treatment. The decline in self-reported craving for opioids was positively correlated with the brain fMRI response to baby schema in the bilateral ventral striatum.

CONCLUSIONS

Opioid antagonist treatment modulated the brain reward system response to a marker of caregiving motivation in patients with opioid use disorder. Neural response to baby schema may offer a novel probe of social motivation and affiliative behaviors in this population.

Daily stressors as antecedents, correlates, and consequences of alcohol and drug use and cravings in community-based offenders

Justice-involved individuals with alcohol and drug use problems reoffend at higher rates than their nonusing counterparts, with alcohol and drug use serving as an important vector to recidivism. At the daily level, exposure to stressors may exacerbate problematic alcohol and drug use; at the individual level, prior treatment experiences may mitigate substance use as individuals adapt to and learn new coping mechanisms. We conducted a daily diary study using Interactive Voice Response technology over 14 consecutive days with 117 men on probation or parole participating in a community-based treatment program (n = 860 calls) and referred to medication-assisted treatment. Participants reported daily stressors, craving for alcohol and illegal drugs, and use of alcohol and illegal drugs 1 time each day. Results of multilevel models showed significant day-to-day fluctuation in alcohol and drug craving and use. In concurrent models, increases in daily stressors were associated with increases in cravings and use of illegal drugs. Prior treatment experience modified many of these relationships, and additional lagged models revealed that those with less treatment experience reported an increase in next-day alcohol craving when they experienced increases in stressors on the previous day compared to those with more treatment experience. Collectively, these findings highlight the importance of tailoring treatment as a function of individual differences, including prior treatment experiences, and targeting daily stressors and subsequent cravings among justice-involved adults with alcohol and drug use problems. (PsycINFO Database Record

Ethical and clinical safety considerations in the design of an effectiveness trial: A comparison of buprenorphine versus naltrexone treatment for opioid dependence

We examine ethical challenges encountered in the design of an effectiveness trial (CTN-0051; X:BOT), comparing sublingual buprenorphine-naloxone (BUP-NX), an established treatment for opioid dependence, to the newer extended-release injectable naltrexone (XR-NTX). Ethical issues surrounded: 1) known poor effectiveness of one possible, commonly used treatment as usual control condition-detoxification followed by counseling without medication; 2) the role of patients' preferences for treatments, given that treatments were clinically approved and available to the population; 3) differences between the optimal "usual treatment" clinical settings for different treatments making it challenging to design a fair comparison; 4) vested interest groups favoring different treatments exerting potential influence on the design process; 5) potentially vulnerable populations of substance users and prisoners; 6) potential therapeutic misconception in the implementation of safety procedures; and 7) high cost of a large trial limiting questions that could be addressed. We examine how the design features underlying these ethical issues are characteristic of effectiveness trials, which are often large trials that compare treatments with varying degrees of existing effectiveness data and familiarity to patients and clinicians, in community-based treatment settings, with minimal exclusion criteria that could involve vulnerable populations. Hence, investigators designing effectiveness trials may wish to remain alert to the possibility of similar ethical issues.

Correlates of retention on extended-release naltrexone among persons living with HIV infection transitioning to the community from the criminal justice system

BACKGROUND

The acceptability of and retention on extended-release naltrexone (XR-NTX), an FDA-approved medication for the treatment of alcohol and opioid use disorders, among persons living with HIV disease (PLH) under criminal justice setting (CJS) supervision has not been evaluated to date.

METHODS

Two double-blind placebo-controlled randomized trials of XR-NTX for inmates with HIV disease transitioning to the community with (1) alcohol use disorders (AUDs) or (2) opioid use disorders, are underway. Reasons for not accepting XR-NTX and an evaluation of differences in demographic features between those who were retained on study drug and those who did not return for their second injection post-release are discussed.

RESULTS

70% of eligible persons consented to participate; almost 90% received their first injection; and almost 60% returned for their first injection after release. Variables found to be associated (p<0.10) with returning for the second injection included: not meeting criteria for hazardous drinking (p=0.035; OR 0.424 (CI 0.191-0.941)); being prescribed antiretroviral therapy (p=0.068; OR 2.170 (CI 0.943-4.992)); expressing experiencing serious depression 30 days prior to incarceration (p=0.068; OR 1.889 (CI 0.955-3.737)); not having a positive cocaine urine screen on the day of release (DOR) (p=0.011; OR 0.258 (CI 0.091-0.729)); and not meeting criteria for an AUD plus any substance use disorder (p=0.068; OR 0.521 (CI 0.259-1.048)). Only positive cocaine urine test on DOR was statistically significant after multivariate regression analyses (p=0.005; OR 0.207 (CI 0.068-0.623)).

CONCLUSION

CJS based XR-NTX programs are highly acceptable among PLH, however retention on XR-NTX after release is negatively impacted by relapse to cocaine use.

[A double-blind randomized placebo-controlled study of the efficacy of the combined treatment with naltrexone and guanfacine for relapse prevention in opiate dependence]

OBJECTIVE

Authors studied the effect of α-2-adrenoreceptor agonist guanfacine on replace prevention in opiate addicts.

MATERIAL AND METHODS

Three hundred and one recently detoxified opiate addicts were randomized under the double-blind double-dummy conditions into one of four treatment groups: naltrexone 50 mg/day+guanfacine 1 mg/day (N+G), naltrexone+guanfacine placebo (N+GP), naltrexone placebo+guanfacine (NP+G), and double placebo (NP+GP). The primary outcome was retention in treatment. The secondary outcomes were perceived stress (Perceived Stress Scale) and craving.

RESULTS

At the end of six months, 20 (26.7%) patients in the N+G group and 15 (19.7%) (p=0.26 to N+G) in N+GP group were retained in treatment compared to 5 (6.7%) in the NP+G group (p=0.002 to N+G group and p=0.017 to N+GP group) and 8 (10.7%) in the double placebo group (p=0.013 to N+G group). There is no significant difference in retention between the N+G group and N+GP group at the end of treatment.

CONCLUSION

Guanfacine had significant craving and stress reducing effect. Naltrexone was more effective than placebo for relapse prevention in opioid dependent patients. The efficacy of the combination of naltrexone and guanfacine was comparable to naltrexone alone. Guanfacine moderately reduced both stress and craving.

Effect of extended-release naltrexone on striatal dopamine transporter availability, depression and anhedonia in heroin-dependent patients

RATIONALE

Extended-release naltrexone (XRNT), an opioid receptor antagonist, is successfully used in the treatment of opioid dependence. However, naltrexone treatment of opioid-dependent patients may reduce striatal dopamine transporter (DAT) availability and cause depression and anhedonia.

OBJECTIVES

The aim of this study is to investigate changes in striatal DAT availability and symptoms of depression (Beck Depression Inventory (BDI)) and anhedonia (Snaith Hamilton Pleasure Scale (SHAPS)) before and during XRNT treatment.

METHODS

At baseline, ten detoxified heroin-dependent patients and 11 matched healthy controls underwent [(123)I]FP-CIT single photon emission computed tomography (SPECT) imaging to assess striatal DAT binding. Patients underwent a second SPECT scan 2 weeks after an intramuscular injection with XRNT.

RESULTS

At baseline, the mean binding potential (BPND) in the putamen was at a trend level lower and the mean BDI score was significantly higher in heroin patients (n = 10) than in controls (n = 11) (3.45 ± 0.88 vs. 3.80 ± 0.61, p = 0.067, d = -0.48 and 12.75 ± 7.40 vs. 5.20 ± 4.83, p = 0.019, d = 1.24, respectively). Post hoc analyses in subgroups with negative urine analyses for opioids and cocaine showed significantly lower baseline putamen BPND in heroin patients (n = 8) than controls (n = 10) (3.19 ± 0.43 vs. 3.80 ± 0.64, p = 0.049, d = -1.03). XRNT treatment in heroin patients was not significantly associated with changes in striatal DAT availability (p = 0.348, d = 0.48), but the mean BDI score after XRNT treatment was significantly lower than before treatment (7.75 ± 7.21 vs. 12.75 ± 7.40, p = 0.004, d = -0.68).

CONCLUSIONS

The results of this study suggest that XRNT treatment does not reduce striatal DAT availability and has no significant effect on anhedonia, but is associated with a significant reduction of depressive symptoms.

Factors associated with willingness to take extended release naltrexone among injection drug users

BACKGROUND

Although opioid-agonist therapy with methadone or buprenorphine/naloxone is currently the mainstay of medical treatment for opioid use disorder, these medications often are not well accepted or tolerated by patients. Recently, extended release naltrexone (XR-NTX), an opioid antagonist, has been advanced as an alternative treatment. The willingness of opioid-addicted patients to take XR-NTX has not been well described.

METHODS

Opioid-using persons enrolled in a community-recruited cohort in Vancouver, Canada, were asked whether or not they would be willing to take XR-NTX. Logistic regression was used to independently identify factors associated with willingness to take the medication.

RESULTS

Among the 657 participants surveyed between June 1, 2013, and November 30, 2013, 342 (52.1%) were willing to take XR-NTX. One factor positively associated with willingness was daily heroin injection (adjusted odds ratio [AOR] = 1.53; 95% confidence interval [CI] = 1.02-2.31), whereas Caucasian ethnicity was negatively associated (AOR = 0.59; 95% CI = 0.43-0.82). Satisfaction with agonist therapy (13.4%) and unwillingness to stop opioids being used for pain (26.9%) were the most common reasons for being unwilling to take XR-NTX.

CONCLUSIONS

A high level of willingness to take XR-NTX was observed in this setting. Interestingly, daily injection heroin use was positively associated with willingness, whereas Caucasian participants were less willing to take XR-NTX. Although explanations for unwillingness were described in this study, further research is needed to investigate real-world acceptability of XR-NTX as an additional option for the treatment of opioid use disorder.

Treating Opioid Dependence With Injectable Extended-Release Naltrexone (XR-NTX): Who Will Respond?

OBJECTIVES

Once-monthly intramuscular extended-release naltrexone (XR-NTX) has demonstrated efficacy for the prevention of relapse in opioid dependence, providing an alternative to agonist or partial agonist maintenance (ie, methadone and buprenorphine). The question remains, for whom is this unique treatment most efficacious and can patient-treatment matching factors be identified?

METHODS

A moderator analysis was conducted on a previously reported 24-week, placebo-controlled, multisite, randomized controlled trial of XR-NTX (n = 126) versus placebo (n = 124) among recently detoxified opioid-dependent adults in Russia, which showed XR-NTX superior to placebo in proportion of opioid abstinent weeks. The moderator analysis examined a dichotomous indicator of good clinical response-achieving at least 90% of weeks abstinent over the 24-week trial. A series of logistic regression models were fit for this outcome as functions of treatment (XR-NTX vs placebo), each baseline moderator variable, and their interactions. The 25 baseline variables included demographics, clinical severity (Addiction Severity Index, SF-36, and Clinical Global Impression-Severity), functioning (EQ-5D), craving, and HIV serostatus (HIV+).

RESULTS

More XR-NTX patients achieved 90% abstinence (64/126, 51%) versus placebo (39/124, 31%; P = 0.002). There were no significant interactions between baseline variables and treatment. There was a significant main effect of Clinical Global Impression-Severity score (P = 0.02), such that higher severity score was associated with a lower rate of Good Clinical Response.

CONCLUSIONS

The absence of significant baseline by treatment interactions indicates that no patient-treatment matching variables could be identified. This suggests that XR-NTX was effective in promoting abstinence from opioids across a range of demographic and severity characteristics.

[Stabilization of remission in patients with opioid dependence with naltrexone implant: a pharmacogenetic approach]

AIM

To evaluate the effect of opioid receptor genes and dopamine system genes polymorphisms on treatment outcomes of opioid dependence with implantable and oral naltrexone.

MATERIAL AND METHODS

Authors carried out a randomized double-blind, double-dummy, placebo-controlled clinical trial. Three hundred and six patients with opioid dependence were randomized into 3 equal treatment groups. The first group received implantation of 1000 mg naltrexone every 2 months during 6 months + oral naltrexone placebo; the second group - placebo implant every 2 months + oral naltrexone (50mg/day) and the third group - placebo implant + oral naltrexone placebo. It was genotyped polymorphisms in the following genes: mu-opioid receptor (OPRM1), kappa-opioid receptor (OPRK1), catechol-O-methyltransferase (COMT), dopamine receptors types 2 (DRD2) and 4 (DRD4), dopamine-beta-hydroxylase, and dopamine transporter (DAT1).

RESULTS

Regardless of treatment several polymorphisms of these genes were associated with high risk of relapse: an allele L (2R) DRD4 120bp (p=0.05; OR (95% CI)=3.3(1.1-10.1)); an allele С DRD2 NcoI (р=0,051; OR (95% CI)=2,86 (1,09-7,52)); the genotype 9.9 DAT VNTR 40bp (р=0,04; OR (95% CI)=1,4 (1,3-1,5)); on the contrary, (СС+СТ)-(ТТ)) variants of OPRK1-DRD2Ncol increased a chance to complete treatment program (р=0,004; OR (95% CI)=7.4 (1.8-30.4)), Kaplan-Meier survival analysis (р=0,016). The probability of completing treatment program by the carriers of these variants was higher in the oral naltrexone group (p=0.016), lower in the double placebo group (p=0.015), but did not influence on treatment outcomes in the naltrexone-implant group.

CONCLUSION

Naltrexone-implant is a highly effective medication for treatment of opioid dependence and its effectiveness exceeds that of oral naltrexone and placebo. The study has shown the joint influence of opioid receptor genes and genes of dopaminergic system on treatment outcomes of opioid dependence. Genetic analysis is useful for determining potential responders to naltrexone treatment of opioid dependence.

Design and methods of a double blind randomized placebo-controlled trial of extended-release naltrexone for HIV-infected, opioid dependent prisoners and jail detainees who are transitioning to the community

BACKGROUND

People with opioid dependence and HIV are concentrated within criminal justice settings (CJS). Upon release, however, drug relapse is common and contributes to poor HIV treatment outcomes, increased HIV transmission risk, reincarceration and mortality. Extended-release naltrexone (XR-NTX) is an evidence-based treatment for opioid dependence, yet is not routinely available for CJS populations.

METHODS

A randomized, double-blind, placebo-controlled trial of XR-NTX for HIV-infected inmates transitioning from correctional to community settings is underway to assess its impact on HIV and opioid-relapse outcomes.

RESULTS

We describe the methods and early acceptability of this trial. In addition we provide protocol details to safely administer XR-NTX near community release and describe logistical implementation issues identified. Study acceptability was modest, with 132 (66%) persons who consented to participate from 199 total referrals. Overall, 79% of the participants had previously received opioid agonist treatment before this incarceration. Thus far, 65 (49%) of those agreeing to participate in the trial have initiated XR-NTX or placebo. Of the 134 referred patients who ultimately did not receive a first injection, the main reasons included a preference for an alternative opioid agonist treatment (37%), being ineligible (32%), not yet released (10%), and lost upon release before receiving their injection (14%).

CONCLUSIONS

Study findings should provide high internal validity about HIV and opioid treatment outcomes for HIV-infected prisoners transitioning to the community. The large number of patients who ultimately did not receive the study medication may raise external validity concerns due to XR-NTX acceptability and interest in opioid agonist treatments.

CLINICAL TRIAL NUMBER

NCT01246401.

The latest achievements in the pharmacotherapy of gambling disorder

Gambling disorder (GD) is becoming increasingly prevalent both among adults and adolescents. Unfortunately, this disorder is largely underestimated, while it can still lead to serious social and personal consequences, including criminal behavior or suicide attempts. In the past, the only means of treating gambling were psychobehavioral therapies. Nowadays, this disorder could also respond to many drugs from different classes such as opioid antagonists, serotonin selective reuptake inhibitors, mood stabilizers, atypical antipsychotics or glutamatergic agents. This review presents current pharmacological strategies and the results of clinical trials evaluating the efficacy of pharmacotherapy for GD. It also discusses the importance of distinguishing different pathological gambler subtypes such as impulsive, obsessive-compulsive and addictive subtypes as this may have serious pharmacological implications.

Naltrexone: a review of existing sustained drug delivery systems and emerging nano-based systems

Narcotic antagonists such as naltrexone (NTX) have shown some efficiency in the treatment of both opiate addiction and alcohol dependence. A few review articles have focused on clinical findings and pharmacogenetics of NTX, advantages and limitations of sustained release systems as well as pharmacological studies of NTX depot formulations for the treatment of alcohol and opioid dependency. To date, three NTX implant systems have been developed and tested in humans. In this review, we summarize the latest clinical data on commercially available injectable and implantable NTX-sustained release systems and discuss their safety and tolerability aspects. Emphasis is also laid on recent developments in the area of nanodrug delivery such as NTX-loaded micelles and nanogels as well as related research avenues. Due to their ability to increase the therapeutic index and to improve the selectivity of drugs (targeted delivery), nanodrug delivery systems are considered as promising sustainable drug carriers for NTX in addressing opiate and alcohol dependence.

Extended-release naltrexone modulates brain response to drug cues in abstinent heroin-dependent patients

Drug cues play an important role in relapse to drug use. Naltrexone is an opioid antagonist that is used to prevent relapse in opioid dependence. Central opioidergic pathways may be implicated in the heightened drug cue-reactivity, but the effects of the opioid receptors' blockade on the brain responses to drug cues in opioid dependence are unknown. To pursue this question, we studied 17 abstinent i.v. heroin users with brain functional magnetic resonance imaging (fMRI) during exposure to visual heroin-related cues and matched neutral images before and 10-14 days after an injection of extended-release naltrexone (XRNTX). Whole brain analysis of variance of fMRI data showed main effect of XRNTX in the medial frontal gyrus, precentral gyrus, cuneus, precuneus, caudate and the amygdala. fMRI response was decreased in the amygdala, cuneus, caudate and the precentral gyrus and increased in the medial frontal gyrus and the precuneus. Higher plasma levels of naltrexone's major metabolite, 6-beta-naltrexol, were associated with larger reduction in the fMRI response to drug cues after XRNTX in the precentral, caudate and amygdala clusters. The present data suggest that XRNTX pharmacotherapy of opioid-dependent patients may, respectively, decrease and potentiate prefrontal and limbic cortical responses to drug cues and that this effect might be related to the XRNTX metabolism. Our findings call for further evaluation of the brain fMRI response to drug-related cues and of the 6-beta-naltrexol levels as potential biomarkers of XRNTX therapeutic effects in patients with opioid dependence.

Phase I study of injectable, depot naltrexone for the relapse prevention treatment of opioid dependence

BACKGROUND AND OBJECTIVES

We tested long-acting injectable depot naltrexone for its tolerability, pharmacokinetics, and safety in Phase I.

METHODS

The Phase I trial enrolled 36 healthy participants in two panels (A, B). In Panel A, 24 subjects were randomly assigned to the high-dosage group (400 mg naltrexone, n=6; placebo, n=6) or low-dosage group (200 mg naltrexone, n=6; placebo, n=6). In Panel B, 12 subjects were randomized to take six doses of monthly injectable naltrexone (400 mg) or placebo.

RESULTS

After a single injection of naltrexone 200 and 400 mg, means (SD) of naltrexone plasma concentrations were .57 (.28) ng/ml and 1.5 (.8) ng/ml 30 days post-injection. There was no effect of accumulation after multiple dosing. Eleven of 30 subjects (36.67%) who were administered injectable depot naltrexone reported a total of 12 adverse events (AEs). Seven of these 11 AEs were coded as possibly related with study medication. All treatment-related AEs were mild in severity. No serious treatment-related AEs occurred.

DISCUSSION AND CONCLUSIONS

This long-acting formulation of injectable depot naltrexone is well tolerated, results in constant plasma concentration of naltrexone for at least 1 month.

SCIENTIFIC SIGNIFICANCE

The tolerability and safety of long-acting injectable depot naltrexone are good.

Naltrexone with or without guanfacine for preventing relapse to opiate addiction in St.-Petersburg, Russia

BACKGROUND

Stress is a key precipitant to discontinuing naltrexone and relapsing to opiate abuse. Alpha-2 adrenergic agonists like guanfacine may reduce stress induced craving and have reduced opiate relapse in small clinical trials.

METHODS

This randomized, double blind double dummy placebo-controlled 6-month trial tested oral naltrexone with or without guanfacine for reducing stress and preventing opiate relapse. We randomized 301 patients to: naltrexone 50 mg/day+guanfacine 1 mg/day (n=75) (N/G), naltrexone+guanfacine placebo (N/P) (n=76), naltrexone placebo+guanfacine (n=75) (P/G), and double placebo (n=75) (P/P).

RESULTS

Among the 75 patients in each group the percentage still retained on naltrexone treatment at six months was: N/G 26.7%, N/P 19.7% (p=0.258 to N/G), P/G 6.7% (p<0.05 to both N groups), and P/P 10.7% (p=0.013 to N+G). Guanfacine reduced the severity of stress particularly at weeks 10 and 18. Adverse events (AE) were infrequent (4.7%) without group differences, with most common AEs: headache, poor appetite, insomnia, and dizziness.

CONCLUSIONS

Adding guanfacine to naltrexone did not improve treatment retention or opiate free urines, but it reduced both stress and craving at later time points in treatment, which may be related to stress-induced craving and the animal model of incubation of reinstatement. During treatment, HIV risk, anxiety, and depression reduced among all patients in treatment, regardless of group.

Long-acting Preparations in Substance Abuse Management: A Review and Update

Many pharmacological approaches have been used in managing substance use disorders. Conventional pharmacological agents have relatively short durations of action which make them vulnerable to non-adherence and relapse to substance use disorder. To overcome this problem, long-acting preparations have been developed with the aim of reducing the frequency of use and hence improving adherence. This review takes a broad overview of the long-acting preparations available for the management of substance use disorders. The pharmacology, advantages and disadvantages of these preparations are discussed. Many of these preparations hold promise for improving patient outcomes.

The science and practice of medication-assisted treatments for opioid dependence

This paper briefly reviews the evolution of opioid addiction treatment from humanitarian to scientific and evidence-based, the evidence bases supporting major medication-assisted treatments and adjunctive psychosocial techniques, as well as challenges faced by clinicians and treatment providers seeking to provide those treatments. Attitudes, politics, policy, and financial issues are discussed.

Opioid detoxification and naltrexone induction strategies: recommendations for clinical practice

BACKGROUND

Opioid dependence is a significant public health problem associated with high risk for relapse if treatment is not ongoing. While maintenance on opioid agonists (i.e., methadone, buprenorphine) often produces favorable outcomes, detoxification followed by treatment with the μ-opioid receptor antagonist naltrexone may offer a potentially useful alternative to agonist maintenance for some patients.

METHOD

Treatment approaches for making this transition are described here based on a literature review and solicitation of opinions from several expert clinicians and scientists regarding patient selection, level of care, and detoxification strategies.

CONCLUSION

Among the current detoxification regimens, the available clinical and scientific data suggest that the best approach may be using an initial 2-4 mg dose of buprenorphine combined with clonidine, other ancillary medications, and progressively increasing doses of oral naltrexone over 3-5 days up to the target dose of naltrexone. However, more research is needed to empirically validate the best approach for making this transition.

Depot naltrexone decreases rewarding properties of sugar in patients with opioid dependence

BACKGROUND

Opioid neurotransmission mediates hedonic value of sweet tastants; their intake may be exaggerated by the consumption of exogenous opioids (e.g., opioid dependence). Sweet Taste Test (STT) is a validated quantitative instrument assessing taste perception and hedonic features of sugar (sucrose) using a randomized and double-blind administration at five different sucrose concentrations ranging from 0.05 to 0.83 M.

METHODS

The STT and cue-induced craving procedure were administered to opioid-dependent patients (n = 15) before and 1 week after the injection of a long-acting depot naltrexone (XRNT) preparation.

RESULTS

Analyses of covariance, employing sucrose concentration and its perceived taste as covariates, showed that XRNT therapy significantly reduced the self-reported hedonic and motivational characteristics of sucrose. Greater reductions in both these characteristics were associated with more diminution in the cue-induced opioid craving.

CONCLUSIONS

Opioid antagonism in opioid-dependent subjects leads to a smaller sweet taste reward, which, in turn, may be proportional to decreased opioid craving. These pilot results support the heuristic value of the STT as a potential marker of the XRNT treatment response and call for further inquiry into potential clinical applications of the test.

Current and potential pharmacological treatment options for maintenance therapy in opioid-dependent individuals

Opioid dependence, manifesting as addiction to heroin and pharmaceutical opioids is increasing. Internationally, there are an estimated 15.6 million illicit opioid users. The global economic burden of opioid dependence is profound both in terms of HIV and hepatitis C virus transmission, direct healthcare costs, and indirectly through criminal activity, absenteeism and lost productivity. Opioid agonist medications, such as methadone and buprenorphine, that stabilize neuronal systems and provide narcotic blockade are the most effective treatments. Prolonged provision of these medications, defined as maintenance treatment, typically produces improved outcomes when compared with short-duration tapers and withdrawal. The benefits of opioid agonist maintenance include decreased illicit drug use, improved retention in treatment, decreased HIV risk behaviours and decreased criminal behaviour. While regulations vary by country, these medications are becoming increasingly available internationally, especially in regions experiencing rapid transmission of HIV due to injection drug use. In this review, we describe the rationale for maintenance treatment of opioid dependence, discuss emerging uses of opioid antagonists such as naltrexone and sustained-release formulations of naltrexone and buprenorphine, and provide a description of the experimental therapies.

Epidemiologic and Molecular Pathophysiology of Chronic Opioid Dependence and the Place of Naltrexone Extended-Release Formulations in its Clinical Management

Naltrexone implants and depot injections (NI) are a novel form of treatment for opiate dependence (OD). Major questions relate to their absolute and relative efficacy and safety. Opportunely, six recent clinical trial data from several continents have uniformly provided dramatic evidence of the potent, dose-related and highly significant efficacy of NI, with minimal or manageable accompanying toxicity and safety concerns. The opiate-free lifestyle is attained significantly more often with NI adjusted O.R. = 6.00 (95% C.I. 3.86–9.50), P < 10⁻¹⁰. Other drug use and drug craving are also rapidly reduced. The optimum manner in which to commence NI remains to be established. Of particular relevance is the relative safety of NI compared to the chronic opiate agonists (COA) usually employed, as the long-term toxicity of COA is only just being elucidated. Large population-based studies have found elevated rates of cardiovascular disease, six cancers, liver and respiratory disease, and all-cause mortality in COA. Whilst opiates have been shown to trigger numerous molecular pathways, the most interesting is the demonstration that the opiate morphinan’s nucleus binds to the endotoxin groove of the TLR4-MD2 heterodimer. This has the effect of triggering a low grade endotoxaemic-like state, which over time may account for these protean clinical findings, an effect which is reversed by opiate antagonists. This emerging evidence suggests an exciting new treatment paradigm for OD and a corresponding increase in the role of NI in treatment.

Medication-assisted treatment research with criminal justice populations: challenges of implementation

Creating, implementing and evaluating substance abuse interventions, especially medication-assisted treatments, for prisoners, parolees, and probationers with histories of heroin addiction is an especially challenging endeavor because of the difficulty in coordinating and achieving cooperation among diverse criminal justice, substance abuse treatment, research, and social service agencies, each with its own priorities and agenda. In addition, there are special rules that must be followed when conducting research with criminal justice-involved populations, particularly prisoners. The following case studies will explore the authors' experience of over 10 years conducting pharmacotherapy research using methadone, buprenorphine, and naltrexone with criminal justice populations. The major obstacles and how they were overcome are presented. Finally, recommendations are provided with regard to implementing and conducting research with criminal justice populations.

Selective review and commentary on emerging pharmacotherapies for opioid addiction

Pharmacotherapies for opioid addiction under active development in the US include lofexidine (primarily for managing withdrawal symptoms) and Probuphine®, a distinctive mode of delivering buprenorphine for six months, thus relieving patients, clinicians, and regulatory personnel from most concerns about diversion, misuse, and unintended exposure in children. In addition, two recently approved formulations of previously proven medications are in early phases of implementation. The sublingual film form of buprenorphine + naloxone (Suboxone®) provides a less divertible, more quickly administered, more child-proof version than the buprenorphine + naloxone sublingual tablet. The injectable depot form of naltrexone (Vivitrol®) ensures consistent opioid receptor blockade for one month between administrations, removing concerns about medication compliance. The clinical implications of these developments have attracted increasing attention from clinicians and policymakers in the US and around the world, especially given that human immunodeficiency virus/acquired immunodeficiency syndrome and other infectious diseases are recognized as companions to opioid addiction, commanding more efforts to reduce opioid addiction. While research and practice improvement efforts continue, reluctance to adopt new medications and procedures can be expected, especially considerations in the regulatory process and in the course of implementation. Best practices and improved outcomes will ultimately emerge from continued development efforts that reflect input from many quarters.

Improving public health through access to and utilization of medication assisted treatment

Providing access to and utilization of medication assisted treatment (MAT) for the treatment of opioid abuse and dependence provides an important opportunity to improve public health. Access to health services comprising MAT in the community is fundamental to achieve broad service coverage. The type and placement of the health services comprising MAT and integration with primary medical care including human immunodeficiency virus (HIV) prevention, care and treatment services are optimal for addressing both substance abuse and co-occurring infectious diseases. As an HIV prevention intervention, integrated (same medical record for HIV services and MAT services) MAT with HIV prevention, care and treatment programs provides the best "one stop shopping" approach for health service utilization. Alternatively, MAT, medical and HIV services can be separately managed but co-located to allow convenient utilization of primary care, MAT and HIV services. A third approach is coordinated care and treatment, where primary care, MAT and HIV services are provided at distinct locations and case managers, peer facilitators, or others promote direct service utilization at the various locations. Developing a continuum of care for patients with opioid dependence throughout the stages MAT enhances the public health and Recovery from opioid dependence. As a stigmatized and medical disenfranchised population with multiple medical, psychological and social needs, people who inject drugs and are opioid dependent have difficulty accessing services and navigating medical systems of coordinated care. MAT programs that offer comprehensive services and medical care options can best contribute to improving the health of these individuals thereby enhancing the health of the community.

Chronic treatment with the opioid antagonist naltrexone favours the coupling of spinal cord μ-opioid receptors to Gαz protein subunits

Sustained administration of opioid antagonists to rodents results in an enhanced antinociceptive response to agonists. We investigated the changes in spinal μ-opioid receptor signalling underlying this phenomenon. Rats received naltrexone (120 μg/h; 7 days) via osmotic minipumps. The antinociceptive response to the μ-agonist sufentanil was tested 24 h after naltrexone withdrawal. In spinal cord samples, we determined the interaction of μ-receptors with Gα proteins (agonist-stimulated [(35)S]GTPγS binding and immunoprecipitation of [(35)S]GTPγS-labelled Gα subunits) as well as μ-opioid receptor-dependent inhibition of the adenylyl cyclase (AC) activity. Chronic naltrexone treatment augmented DAMGO-stimulated [(35)S]GTPγS binding, potentiated the inhibitory effect of DAMGO on the AC/cAMP pathway, and increased the inverse agonist effect of naltrexone on cAMP accumulation. In control rats, the inhibitory effect of DAMGO on cAMP production was antagonized by pertussis toxin (PTX) whereas, after chronic naltrexone, the effect became resistant to the toxin, suggesting a coupling of μ-receptors to PTX-insensitive Gα(z) subunits. Immunoprecipitation assays confirmed the transduction switch from Gα(i/o) to Gα(z) proteins. The consequence was an enhancement of the antinociceptive response to sufentanil that, in consonance with the neurochemical data, was prevented by Gα(z)-antisense oligodeoxyribonucleotides but not by PTX. Such changes in opioid receptor signalling can be a double-edged sword. On the one hand, they may have potential applicability to the optimisation of the analgesic effects of opioid drugs for the control of pain. On the other hand, they represent an important homeostatic dysregulation of the endogenous opioid system that might account for undesirable effects in patients chronically treated with opioid antagonists. This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'.

Use of naltrexone to treat opioid addiction in a country in which methadone and buprenorphine are not available

Opioid dependence is one of the most severe drug dependencies. Naltrexone is a medication that completely blocks the subjective and other effects of opioids and, when administered to detoxified opioid addicts and taken as directed, prevents relapse and helps maintain abstinence. The major problem with naltrexone is poor compliance, particularly in countries in which there is a treatment alternative based on substitution of illicit opioids such as heroin with orally administered opioid agonists (methadone) or partial agonist/antagonists (buprenorphine). In Russia, substitution therapy is forbidden by law, and naltrexone is the only available pharmacotherapy for heroin dependence. Due to the lack of alternatives to naltrexone and stronger family control of compliance (adherence), naltrexone is more effective for relapse prevention and abstinence stabilization in Russia than in Western countries. Long-acting, sustained-release formulations (injectable and implantable) seem particularly effective compared with oral formulations. This article summarizes the results of studies conducted in Russia during the past 10 years that demonstrate these points.