Naltrexone implants can completely prevent early (1-month) relapse after opiate detoxification: a pilot study of two cohorts totalling 101 patients with a note on naltrexone blood levels

Monitoring and Improving Naltrexone Adherence in Patients with Substance Use Disorder

OBJECTIVE

Naltrexone is an opioid antagonist used for the treatment of patients with opioid use disorder and alcohol use disorder. This population often presents problems of follow-up and therapeutic efficacy related to adherence to treatment. The purpose of our study is to provide an exhaustive summary of the current evidence regarding naltrexone adherence in people with substance use disorders and to identify possible variables that may influence adherence to naltrexone.

METHODS

Two searches were performed in bibliographic databases (PubMed, Embase), and studies included in the systematic review were those published from January 1, 2011 to September 2020, with participants over 18 years of age, evaluating treatment with naltrexone in alcohol use disorder and opioid use disorder. From the total of 133 articles initially selected, 36 were included and analyzed in the systematic review.

RESULTS

Naltrexone has not demonstrated superiority over other available treatments in terms of adherence and abstinence, although reinforcement systems have obtained favorable results as an additional strategy to improve adherence.

CONCLUSION

It is necessary to study other psychosocial variables involved in improving adherence, in addition to taking patient preferences into account in order to improve the external validity of the results.

Medication-assisted therapies for opioid use disorders in patients with chronic pain

Opioids have been used to treat pain and invoke pleasure for centuries. Modern scientific advancements have led to more potent, synthetic opioids. While certainly more effective in treating pain, they can also be much more addictive. Over the years the scientific community has developed a clearer understanding of the role opioid receptors play in causing and treating opioid use disorders (OUD) and we now know that OUD can develop in individuals taking opioids for "legitimate" pain. Current guidelines suggest that all prescribers (especially those prescribing opioids) be capable treating OUD. Pharmacological advances have led to a wide array of safe and effective treatment options to address OUDs. This paper will discuss the history of opioid development, what is known about the transition from analgesic uses to addiction and modern evidenced based treatment strategies to address OUDs.

Medication-Assisted Treatment for Opioid-Use Disorder

The United States is in the midst of a national opioid epidemic. Physicians are encouraged both to prevent and treat opioid-use disorders (OUDs). Although there are 3 Food and Drug Administration-approved medications to treat OUD (methadone, buprenorphine, and naltrexone) and there is ample evidence of their efficacy, they are not used as often as they should. We provide a brief review of the 3 primary medications used in the treatment of OUD. Using data from available medical literature, we synthesize existing knowledge and provide a framework for how to determine the optimal approach for outpatient management of OUD with medication-assisted treatments.

Slow-release naltrexone implant versus oral naltrexone for improving treatment outcomes in people with HIV who are addicted to opioids: a double-blind, placebo-controlled, randomised trial

BACKGROUND

Untreated opioid addiction in people with HIV is associated with poor HIV treatment outcomes. Slow-release, long-acting, implantable naltrexone might improve these outcomes. Here, we present results of a study aimed to test this hypothesis.

METHODS

We did a 48 week double-blind, double-dummy, placebo-controlled, phase 3, randomised trial with men and women addicted to opioids who were starting antiretroviral therapy (ART) for HIV and whose viral loads were higher than 1000 copies per mL. Participants were seeking treatment at two HIV and two narcology programme centres in Saint Petersburg, Russia, and the surrounding Leningrad region. The Pavlov statistical department created a table with stratification on gender distribution, viral load, and CD4 cell count. We stratified participants according to gender, viral load, and CD4 cells per μL, and randomly assigned (1:1) them to addiction treatment with a naltrexone implant and oral naltrexone placebo (implant group) or oral naltrexone and placebo implant (oral group). The primary outcome was plasma viral load of less than 400 copies per mL at 24 weeks and 48 weeks. We included all randomly assigned participants in outcome analyses (intention to treat). Treatment staff and patients were masked to group assignment. The study is complete and registered at ClinicalTrials.gov, NCT01101815.

FINDINGS

Between July 14, 2011, and April 14, 2014, 238 potential participants were recruited and screened, 35 were excluded for not meeting inclusion criteria, three declined to participate, and 200 were randomly assigned to treatment (100 to each group). At week 24, 38 (38) participants in the implant group and 35 (35%) in the oral group had viral loads less than 400 copies per mL (risk ratio 1·1, 95% CI 0·76-1·56; p=0·77). At week 48, 66 participants in the implant group and 50 in the oral group had viral loads less than 400 copies per mL (risk ratio 1·32, 95% CI 1·04-1·68; p=0·045). There were seven serious adverse events: three deaths in the implant group (one due to heart disease, one trauma, and one AIDS), and four in the oral group (two overdoses, one pancreatic cancer, and one AIDS). The overdose deaths occurred 9-10 months after the last naltrexone dose.

INTERPRETATION

The longer the blockade of opioid effects, the more protection an individual gets from missed ART doses and impulsive behaviours that lead to relapse and poor, even fatal, outcomes. Commercial development of implants could result in a meaningful addition to addiction treatment options.

FUNDING

National Institutes of Health, National Institute on Drug Abuse, Penn Centre for AIDS Research, and Penn Mental Health AIDS Research Centre.

Naltrexone ameliorates functional network abnormalities in alcohol-dependent individuals

Naltrexone, an opioid receptor antagonist, is commonly used as a relapse prevention medication in alcohol and opiate addiction, but its efficacy and the mechanisms underpinning its clinical usefulness are not well characterized. In the current study, we examined the effects of 50‐mg naltrexone compared with placebo on neural network changes associated with substance dependence in 21 alcohol and 36 poly‐drug‐dependent individuals compared with 36 healthy volunteers. Graph theoretic and network‐based statistical analysis of resting‐state functional magnetic resonance imaging (MRI) data revealed that alcohol‐dependent subjects had reduced functional connectivity of a dispersed network compared with both poly‐drug‐dependent and healthy subjects. Higher local efficiency was observed in both patient groups, indicating clustered and segregated network topology and information processing. Naltrexone normalized heightened local efficiency of the neural network in alcohol‐dependent individuals, to the same levels as healthy volunteers. Naltrexone failed to have an effect on the local efficiency in abstinent poly‐substance‐dependent individuals. Across groups, local efficiency was associated with substance, but no alcohol exposure implicating local efficiency as a potential premorbid risk factor in alcohol use disorders that can be ameliorated by naltrexone. These findings suggest one possible mechanism for the clinical effects of naltrexone, namely, the amelioration of disrupted network topology.

Opioid Addiction: Social Problems Associated and Implications of Both Current and Possible Future Treatments, including Polymeric Therapeutics for Giving Up the Habit of Opioid Consumption

BACKGROUND

Detoxification programmes seek to implement the most secure and compassionate ways of withdrawing from opiates so that the inevitable withdrawal symptoms and other complications are minimized. Once detoxification has been achieved, the next stage is to enable the patient to overcome his or her drug addiction by ensuring consumption is permanently and completely abandoned, only after which can the subject be regarded as fully recovered.

METHODS

A systematic search on the common databases of relevant papers published until 2016 inclusive.

RESULTS AND CONCLUSION

Our study of the available oral treatments for opioid dependence has revealed that no current treatment can actually claim to be fully effective. These treatments require daily oral administration and, consequently, regular visits to dispensaries, which in most cases results in a lack of patient compliance, which causes fluctuations in drug plasma levels. We then reviewed alternative treatments in the available scientific literature on polymeric sustained release formulations. Research has been done not only on release systems for detoxification but also on release systems for giving up the habit of taking opioids. These efforts have obtained the recent authorization of polymeric systems for use in patients that could help them to reduce their craving for drugs.

Pharmacological treatments for drug misuse and dependence

INTRODUCTION

Substance misuse disorder (DSM-5) remains a major health challenge. Harm reduction is the initial treatment goal, by reducing or eliminating non-prescribed drug use. Eventual abstinence is the ultimate harm reduction goal. However the scope for evidence-based pharmacological interventions remains limited.

AREAS COVERED

The paper takes a pragmatic clinical approach to existing and developing pharmacotherapies for substance misuse. Dependence may be characterised as a cycle with three stages: binge/intoxication, withdrawal/negative affect and preoccupation/anticipation (craving). Each of these stages may be the focus of pharmacotherapeutic intervention, and current literature is discussed which is of relevance to the practising clinician. Dependence on opiates, stimulants, cannabis and prescribed medications including benzodiazepines and the current treatments are addressed.

EXPERT OPINION

Possible pharmacotherapies of the future include anti-craving medications, which are still incompletely understood. Other developments include ultra-long-acting formulations, some of which have already been produced and are being studied or are in early clinical practice. A completely new line of investigation has been drug 'vaccines', whereby the body is stimulated to produce antibodies to, for example, cocaine and nicotine. Despite a number of evidence-based strategies for the treatment of substance misuse disorder, the range of licensed pharmacological treatment choices nevertheless remains narrow.

A placebo-controlled trial of memantine as an adjunct to injectable extended-release naltrexone for opioid dependence

There is preclinical support for using NMDA receptor glutamatergic antagonists to aid in naltrexone-based treatment of opioid dependence. We hypothesized that adding memantine will improve efficacy of extended-release (XR) naltrexone to prevent relapse. In this double blind study opioid-dependent participants (N=82) underwent inpatient detoxification and naltrexone induction. During naltrexone initiation participants were randomized to receive memantine 40 mg or placebo and continued treatment for 12-weeks with XR naltrexone and relapse-prevention therapy. Sixty eight percent of participants completed detoxification and received the first dose of XR naltrexone. Rates of trial completion were significantly greater in participants receiving placebo than memantine (70% vs. 43%, p<0.05). Severity of opioid withdrawal symptoms during the first 3 weeks of the trial appeared to be lower in the group receiving memantine (p=0.07). Adding memantine does not appear to increase the effectiveness of injectable XR naltrexone as a relapse prevention strategy in opioid dependence and may lead to an increase in treatment drop-out.

Rapid opiate detoxification and antagonist induction under general anaesthesia or intravenous sedation is humane, sometimes essential and should always be an option. Three illustrative case reports involving diabetes and epilepsy and a review of the literature

When abstinence is an appropriate goal, controlled studies and systematic reviews confirm that rapid, antagonist-precipitated opiate withdrawal procedures are the most effective and cost effective methods of initiating abstinence, and naltrexone (NTX) maintenance. While 'rapid' withdrawal, better conceptualised as Rapid Antagonist Induction (RAI), can often be humanely achieved with modest sedation levels, we present three case histories to support our argument that for some patients, general anaesthesia (GA), or techniques of intravenous sedation (IVS) that approach GA, are essential for safety and success. This includes patients with intercurrent disease (e.g. epilepsy or insulin-dependent diabetes) but also those with severe withdrawal phobia after previous distressing experiences. We discuss the history of the procedure. The dangers of RAI under GA or IVS in experienced hands have been exaggerated and the appropriate expertise should be more easily available. Patients and clinicians readily accept risks of major surgery for the excessive intake of food that causes most obesity. Similar risk-acceptance exists in cosmetic surgery and obstetrics. The increasing use and effectiveness of long-acting implants or depot-injections of NTX for relapse-prevention have largely solved compliance problems that undermined the potential of oral NTX. Their ability to prevent opiate overdose in abstinent, non-tolerant patients also strengthens arguments both for offering RAI as a therapeutic option and for reducing psychological, professional and practical barriers to using it.

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.

Naltrexone depot formulations for opioid and alcohol dependence: a systematic review

Naltrexone is an opioid receptor antagonist that blocks the reinforcing effects of opioids and reduces alcohol consumption and craving. It has no abuse potential, mild and transient side effects, and thus appears an ideal pharmacotherapy for opioid dependence. Its effectiveness in alcohol dependence is less evident, but compliance with naltrexone combined with psychosocial support has been repeatedly shown to improve drinking outcomes. Limited compliance with oral naltrexone treatment is a known drawback. Several naltrexone implant and injectable depot formulations are being investigated and provide naltrexone release for at least 1 month. Studies among opioid-dependent patients indicate significant reductions in heroin use, but sample sizes are usually small. In alcohol dependence, two large multicenter trials report alcohol and craving reductions for naltrexone and placebo groups, indicating a significant but moderate effect. The pharmacokinetic profile of the injectable formulation indicates reliable naltrexone release over 1 month at therapeutic levels. Implant formulations releasing naltrexone up to 7 months are reported. Findings on safety and tolerability confirm the generally mild adverse effects described for naltrexone tablets. However, further research on therapeutic levels (i.e., opioid blocking) is warranted. The majority of naltrexone implants lacks approval for regular clinical use and larger longitudinal studies are needed. The available naltrexone depot formulations have the potential to significantly improve medication compliance in opioid and alcohol dependence. In certain circumstances, they may constitute a promising new treatment option.

Delivery systems and dosing for antipsychotics

Schizophrenia is a devastating illness, affecting approximately 1-2 % of the world population. Age of onset is generally between 20 and 30 years of age with a chronic, unremitting course for the duration of the patient's life. Although schizophrenia is among the most severe and debilitating illnesses known to medicine, its treatment has remained virtually unchanged for over 50 years. This chapter covers several major concepts in experimental drug development and delivery: (1) the concept of "typical" vs. "atypical" classifications for antipsychotic drugs as it relates to dosing; (2) the development of depot formulations for improved medication adherence; and (3) several promising areas for future therapeutic advances related to the methods and duration of drug administration. These areas include sublingual, injectable, and implantable drug delivery strategies that have the potential to effect rapid and dramatic improvements in schizophrenia outcomes.

The association between outpatient buprenorphine detoxification duration and clinical treatment outcomes: a review

BACKGROUND

The association between buprenorphine taper duration and treatment outcomes is not well understood. This review evaluated whether duration of outpatient buprenorphine taper is significantly associated with treatment outcomes.

METHODS

Studies that were published in peer-reviewed journals, administered buprenorphine as an outpatient taper to opioid-dependent participants, and provided data on at least one of three primary treatment outcome measures (opioid abstinence, retention, peak withdrawal severity) were reviewed. Primary treatment outcomes were evaluated as a function of taper duration using hierarchical linear regressions with pre-taper maintenance duration as a cofactor.

RESULTS

Twenty-eight studies were reviewed. Taper duration significantly predicted percent of opioid-negative samples provided during treatment, however pre-taper maintenance period predicted percent participants abstinent on the final day of treatment. High rates of relapse were reported. No significant association between taper duration and retention in treatment or peak withdrawal severity was observed.

CONCLUSION

The data reviewed here suggest taper duration is associated with opioid abstinence achieved during detoxification but not with other markers of treatment outcome. The reviewed studies varied widely on several parameters (e.g., frequency of urinalysis testing, provision of ancillary medications) that may influence treatment outcome and thus could have interfered with the ability to identify relationships between taper duration and outcomes. Future studies evaluating opioid detoxification should utilize rigorous experimental methods and report a wider range of outcome measures in order to help advance our understanding of the association between taper duration and treatment outcomes.

Mandatory naltrexone treatment prevents relapse among opiate-dependent anesthesiologists returning to practice

OBJECTIVE

Anesthesiologists with opioid use disorders are at high risk for relapse. In 2005, the impaired professionals monitoring program of the State of Florida implemented a policy whereby anesthesiologists referred for opiate use disorders were contractually obligated to take naltrexone for 2 years. Naltrexone ingestion was witnessed and verified via random urine drugs screens or administered via intramuscular injection.

METHOD

Charts were reviewed for the 11 anesthesiologists who underwent mandated pharmacotherapy with naltrexone, and 11 anesthesiologists who began monitoring immediately before implementation of this policy.

RESULTS

Eight of 11 anesthesiologists who did not take naltrexone experienced a relapse on opiates. Only 1 of 11 anesthesiologists experienced a relapse on opiates after taking naltrexone, whereas another relapsed on an inhalant (nitrous oxide). It is noteworthy that 5 of the 11 anesthesiologists who took naltrexone had relapsed before naltrexone treatment, and 7 of the 11 anesthesiologists who did not take naltrexone experienced multiple documented relapses. Only 1 of the 11 anesthesiologists who did not take naltrexone successfully returned to the practice of anesthesiology. This individual suffered primarily from alcohol dependence, and suspected opiate abuse was never verified. Others who attempted return to anesthesiology (n = 7) suffered a relapse. In comparison, 9 of the 11 anesthesiologists who took naltrexone have returned to the practice of anesthesiology without a relapse (as verified by continued random urine and hair testing).

CONCLUSION

Mandatory naltrexone treatment may provide anesthesiologists with an additional safeguard to successfully return to work.

Pharmacological enhancement of naltrexone treatment for opioid dependence: a review

PURPOSE: Opioid dependence (OD) is a serious and growing clinical condition with increasing social costs that requires expanding treatment beyond opioid agonist substitution. The opioid antagonist naltrexone has displayed a remarkable association of theoretical effectiveness and poor clinical utility in treating OD due to noncompliant behavior and low acceptability among patients, only partly modified by psychosocial interventions. We reviewed pharmacological studies, including naltrexone depot formulations and combination treatments. METHOD: We searched PubMed for clinical studies on the use of naltrexone implants and slow-release injections in OD, and investigations using adjunct medications to improve naltrexone maintenance therapy of OD. We discussed the results in view of their application to the clinical practice. RESULTS: Significant reduction in opioid use and improved retention in treatment have been found in several studies using depot naltrexone formulations, some of which are controlled clinical trials. Pilot investigations have gathered initial positive results on the use of naltrexone in combination with serotonin reuptake inhibitors, α-2 adrenergic, opioid, and γ-aminobutyric acid agonist medications. CONCLUSION: Current evidence suggests that more research on effectiveness and safety is needed in support of depot naltrexone treatment for OD. Further research comparing slow-release with oral naltrexone and opioid agonist medications will help characterize the role of opioid antagonist-mediated treatment of OD. Preliminary investigations on naltrexone combination treatments suggest the opportunity to continue study of new mixed receptor activities for the treatment of OD and other drug addictions.

Studies on in vitro availability, degradation, and thermal properties of naltrexone-loaded biodegradable microspheres

PURPOSE

Following the report that continuous exposure of naltrexone (NTX) to drug-dependent pregnant women is safe and effective, the work was designed to develop NTX-loaded controlled delivery systems capable of making NTX available from 1 month to 4 months or greater by a single parenteral administration. Such drug-delivery systems will be useful in alleviating problems such as fetal alcohol syndrome in pregnant women and other problems associated with alcoholism.

METHODS

These studies were designed to investigate in vitro drug availability and microsphere degradation (investigated by gel permeation chromatography (GPC) peak areas of water-soluble fragments released into incubation medium, changes in molecular weight with degradation time, and changes in the glass transition temperature with degradation time) of NTX-loaded poly(D,L-lactide-co-glycolide) (PDLLAGA) microspheres.

RESULTS

Data showed that in vitro drug availability and degradation were affected by the initial molecular weight of the copolymers, the type of copolymers (lactide-co-glycolide ratio), the source of the polymer (the manufacturer), and the nature of the drug (anhydrous versus regular NTX).

CONCLUSION

Drug-development scientists interested in NTX-loaded microspheres for the design of controlled release devices using these polyesters should take adequate cognizance of the variables that affect drug availability from NTX-loaded microspheres. The copolymers are suitable for the fabrication of NTX-loaded microspheres capable of sustained drug release from 30 to 150 days.

Long-acting injectable versus oral naltrexone maintenance therapy with psychosocial intervention for heroin dependence: a quasi-experiment

OBJECTIVE

To conduct a quasi-experimental comparison of early clinical outcomes between injectable, sustained-release, depot naltrexone formulation versus oral naltrexone maintenance therapy in individuals with opiate dependence.

METHOD

Early retention in treatment and urine-confirmed opiate use in the first 8 weeks postdetoxification were compared between patients (diagnosed as opiate-dependent according to DSM-IV criteria) participating in 2 concurrently run randomized clinical trials of oral (n = 69; patients treated from September 1999 to May 2002) and long-acting injectable (n = 42; patients treated from November 2000 to June 2003) naltrexone maintenance therapy with psychosocial therapy.

RESULTS

Long-acting injectable naltrexone produced significantly better outcome than oral naltrexone on days retained in treatment (F(1,106) = 6.49, P = .012) and for 1 measure of opiate use (F(1,106) = 5.26, P = .024); other measures were not significantly different, but differences were in the same direction. In subanalyses, there were interaction effects between baseline heroin use severity and type of treatment. In subanalyses, heroin users with more severe baseline use showed better retention with oral naltrexone maintenance therapy combined with intensive psychotherapy (behavioral naltrexone therapy) as compared to retention shown by severe heroin users treated with long-acting naltrexone injections combined with standard cognitive-behavioral therapy (χ²(1)= 9.31, P = .002); less severe heroin users evidenced better outcomes when treated with long-acting injectable naltrexone.

CONCLUSIONS

This quasi-experimental analysis provides tentative indications of superior outcomes for heroin-dependent patients treated with long-acting injectable naltrexone compared to oral naltrexone. The finding that heroin users with more severe baseline use achieved better outcomes with oral naltrexone is most probably attributable to the intensive nature of the psychosocial treatments provided and points to the opportunity for continued research in augmenting injectable naltrexone with psychosocial strategies to further improve outcome, especially in individuals with more severe use. The results should be considered exploratory given the quasi-experimental nature of the study.

Opioid antagonists under heavy sedation or anaesthesia for opioid withdrawal

BACKGROUND

Withdrawal (detoxification) is necessary prior to drug-free treatment or as the end point of long-term substitution treatment.

OBJECTIVES

To assess the effectiveness of opioid antagonists to induce opioid withdrawal with concomitant heavy sedation or anaesthesia, in terms of withdrawal signs and symptoms, completion of treatment and adverse effects.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 3, 2009), Medline (January 1966 to 11 August 2009), Embase (January 1985 to 2009 Week 32), PsycINFO (1967 to July 2009), and reference lists of articles.

SELECTION CRITERIA

Controlled studies of antagonist-induced withdrawal under heavy sedation or anaesthesia in opioid-dependent participants compared with other approaches, or a different regime of anaesthesia-based antagonist-induced withdrawal.

DATA COLLECTION AND ANALYSIS

One reviewer assessed studies for inclusion, undertook data extraction and assessed quality. Inclusion decisions and the overall process were confirmed by consultation between all authors.

MAIN RESULTS

Nine studies (eight randomised controlled trials) involving 1109 participants met the inclusion criteria for the review.Antagonist-induced withdrawal is more intense but less prolonged than withdrawal managed with reducing doses of methadone, and doses of naltrexone sufficient for blockade of opioid effects can be established significantly more quickly with antagonist-induced withdrawal than withdrawal managed with clonidine and symptomatic medications. The level of sedation does not affect the intensity and duration of withdrawal, although the duration of anaesthesia may influence withdrawal severity. There is a significantly greater risk of adverse events with heavy, compared to light, sedation (RR 3.21, 95% CI 1.13 to 9.12, P = 0.03) and probably with this approach compared to other forms of detoxification.

AUTHORS' CONCLUSIONS

Heavy sedation compared to light sedation does not confer additional benefits in terms of less severe withdrawal or increased rates of commencement on naltrexone maintenance treatment. Given that the adverse events are potentially life-threatening, the value of antagonist-induced withdrawal under heavy sedation or anaesthesia is not supported. The high cost of anaesthesia-based approaches, both in monetary terms and use of scarce intensive care resources, suggest that this form of treatment should not be pursued.

Antipsychotic dosing and drug delivery

This chapter addresses the current state of affairs regarding proposed mechanism of action for antipsychotic medications and how this mechanism relates to dosing and delivery strategies. The initial portion describes the history of antipsychotic medication, including key discoveries that contribute to the dopamine hypothesis of schizophrenia and provide evidence that dopamine D2 receptor antagonism remains the most copasetic explanation for both determination of dose and degree of efficacy for current antipsychotic medications. Early observations regarding the unique properties of clozapine and how those observations led to the misconception and misnomer of atypicality are also discussed. Subsequent sections relate the dosing of available medications using chlorpromazine equivalents, with a discussion of non-D2-related mechanisms to antipsychotic effects. The balance of the chapter explores the temporal pattern of receptor occupancy as a key determinant of antipsychotic effectiveness, noting that continuous infusion would present the optimal method of treatment. In addition to the pharmacodynamic benefits of continuous long-term delivery systems, the incidence, causes, and clinical consequences of poor adherence are addressed. These observations are then discussed in the context of clinical studies and meta-analyses, demonstrating superiority of long-term depot preparations over oral administration. However, despite overwhelming evidence in favor of long-term delivery systems, few options are available to provide such ideal medication delivery profiles. Barriers to creating traditional depot preparations for a large number of antipsychotic agents, as well as efforts to address these limitations with polymer-based microspheres are described. The potential extension of current formulations to very long-term delivery implants using biodegradable and nonbiodegradable platforms is then described. Benefits as well as limitations of such systems are discussed with respect to clinical and ethical issues as well as a brief description of potential regulatory and logistic barriers to developing better delivery options. In summary, this chapter describes the basis for relating the dose of all existing antipsychotic medications to dopamine D2 receptor affinity and the potential contribution of continuous occupancy to enhanced efficacy through superior biological effects and improved adherence.

Opioid dependence treatment: options in pharmacotherapy

The development of effective treatments for opioid dependence is of great importance given the devastating consequences of the disease. Pharmacotherapies for opioid addiction include opioid agonists, partial agonists, opioid antagonists, and alpha-2-adrenergic agonists, which are targeted toward either detoxification or long-term agonist maintenance. Agonist maintenance therapy is currently the recommended treatment for opioid dependence due to its superior outcomes relative to detoxification. Detoxification protocols have limited long-term efficacy, and patient discomfort remains a significant therapy challenge. Buprenorphine's effectiveness relative to methadone remains a controversy and may be most appropriate for patients in need of low doses of agonist treatment. Buprenorphine appears superior to alpha-2 agonists, however, and office-based treatment with buprenorphine in the USA is gaining support. Studies of sustained-release formulations of naltrexone suggest improved effectiveness for retention and sustained abstinence; however, randomized clinical trials are needed.

Behavioral Therapy to Augment Oral Naltrexone for Opioid Dependence: A Ceiling on Effectiveness?

The effectiveness of antagonist maintenance with oral naltrexone for opioid dependence has been limited by high dropout rates. Behavioral Naltrexone Therapy (BNT) was developed to improve retention on oral naltrexone by integrating voucher incentives, Motivational and Cognitive Behavioral therapies, and a significant other for monitoring medication adherence. In a 6-month, randomized, controlled trial in heroin dependent patients, BNT (N = 36) improved retention in treatment compared to a standard treatment control (Compliance Enhancement (CE); N = 33) (log rank = 4.28; p = .04). Most patients retained beyond 3 months achieved abstinence from opioids, but retention at 6 months was only 22% on BNT and 9% on CE. A systematic review of related controlled trials revealed similar effect sizes in the small to medium range, and substantial dropout. There may be a limit on the extent to which behavioral therapy can overcome poor adherence to oral naltrexone. Future research should consider combinations of behavioral methods with new long-acting injectable or implantable naltrexone formulations.

Naltrexone implants after in-patient treatment for opioid dependence: randomised controlled trial

BACKGROUND

Naltrexone has considerable potential in helping to prevent relapse in heroin dependency. A longer-lasting formulation for naltrexone treatment is desirable to further reduce non-adherence and relapse during treatment of opiate dependence.

AIMS

To evaluate the safety and effectiveness of a 6-month naltrexone implant in reducing opioid use after in-patient treatment.

METHOD

A group of 56 abstinence-oriented patients who completed in-patient treatment for opioid dependence were randomly and openly assigned to receive either a 6-month naltrexone implant or their usual aftercare. Drug use and other outcomes were assessed at 6-month follow-up.

RESULTS

Patients receiving naltrexone had on average 45 days less heroin use and 60 days less opioid use than controls in the 180-day period (both P<0.05). Blood tests showed naltrexone levels above 1 ng/ml for the duration of 6 months. Two patients died, neither of whom had received an implant.

CONCLUSIONS

Naltrexone implant treatment safely and significantly reduces opioid use in a motivated population of patients.

Improved parameters of metabolic glycaemic and immune function and arterial stiffness with naltrexone implant therapy

Here the dramatic and rapid response of a 54-year-old obese hypertensive man with poorly controlled insulin-dependent diabetes with a 33 year history of high dose heroin use, a 1 year history of refractory ulceration of his hands, ankles and feet, treated coronary artery disease, and the metabolic syndrome, to implantation with long-acting naltrexone implants is presented. In particular his hyperlipidaemia, hyperglycaemia, proinflammatory state, evidence of hepatic and renal insufficiency, arterial stiffness, and extensive and chronic cutaneous ulceration all improved dramatically over just 13 weeks, in association with complete control of his heroin, benzodiazepine, tobacco and cannabis use. The metabolic and vascular benefits were all highly statistically significant. The case is the first to document dramatic and rapid metabolic, immune and vascular improvements in association with clinical naltrexone therapy and are consistent with its likely effects in restoring addiction-related stem cell and immunological deficits.

Sustained-release naltrexone for opioid dependence

BACKGROUND

Naltrexone is an opioid antagonist which effectively blocks heroin effects. Since opioid dependence treatment with naltrexone tablets suffers from high dropout rates, several depot injections and implants are under investigation. Sustained-release formulations are claimed to be effective, but a systematic review of the literature is lacking.

OBJECTIVES

To evaluate the effectiveness of sustained-release naltrexone for opioid dependence and its adverse effects in different study populations.

SEARCH STRATEGY

The following databases were searched from their inception to November 2007: Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, CINAHL, LILACS, PsycINFO, ISI Web of Science, trial database at http://clinicaltrials.gov, available NIDA monographs, CPDD and AAAP conference proceedings. The reference lists of identified studies, published reviews and relevant web sides were searched manually. Study authors and drug companies were contacted to obtain any unpublished material or missing data.

SELECTION CRITERIA

To evaluate effectiveness only RCTs were included. To evaluate safety, any clinical trial reporting adverse effects was assessed. Treatment condition was extended to include alcohol dependent subjects and healthy volunteers.

DATA COLLECTION AND ANALYSIS

Reviewers independently evaluated the reports, rated methodological quality and extracted data. Analyses were performed separately for opioid dependent, alcohol dependent and healthy participants.

MAIN RESULTS

Foe effectiveness, one report met inclusion criteria. Two dosages of naltrexone depot injections (192 and 384 mg) were compared to placebo. High-dose significantly increased days in treatment compared to placebo (WMD 21.00, 95% CI 10.68 to 31.32, p<0.0001). High-dose compared to low-dose significantly increased days in treatment (WMD 12.00, 95% CI 1.69 to 22.31, p=0.02). Number of patients retained in treatment did not show significant differences between groups. For adverse effects, seventeen reports met inclusion criteria analyses, six were RCTs. Side effects were significantly more frequent in naltrexone depot groups compared to placebo. In alcohol dependent samples only, adverse effects appeared to be significantly more frequent in the low-dose naltrexone depot groups compared to placebo (RR 1.18, 95% CI 1.02 to 1.36, p=0.02). In the opioid dependent sample, group differences were not statistically significant. Reports on systematic assessment of side effects and adverse events were scarce.

AUTHORS' CONCLUSIONS

There is insufficient evidence to evaluate the effectiveness of sustained-release naltrexone for treatment of opioid dependence. For naltrexone injections, administration site-related adverse effects appear to be frequent, but of moderate intensity and time limited. For a harm-benefit evaluation of naltrexone implants, more data on side effects and adverse events are needed.

Psychosocial and treatment correlates of opiate free success in a clinical review of a naltrexone implant program

BACKGROUND

There is on-going controversy in relation to the efficacy of naltrexone used for the treatment of heroin addiction, and the important covariates of that success. We were also interested to review our experience with two depot forms of implantable naltrexone.

METHODS

A retrospective review of patients' charts was undertaken, patients were recalled by telephone and by letter, and urine drug screen samples were collected. Opiate free success (OFS) was the parameter of interest. Three groups were defined. The first two were treated in the previous 12 months and comprised "implant" and "tablet" patients. A third group was "historical" comprising those treated orally in the preceding 12 months.

RESULTS

There were 102, 113 and 161 patients in each group respectively. Groups were matched for age, sex, and dose of heroin used, but not financial status or social support. The overall follow-up rate was 82%. The Kaplan Meier 12 month OFS were 82%, 58% and 52% respectively. 12 post-treatment variables were independently associated with treatment retention. In a Cox proportional hazard multivariate model social support, the number of detoxification episodes, post-treatment employment, the use of multiple implant episodes and spiritual belief were significantly related to OFS.

CONCLUSION

Consistent with the voluminous international literature clinically useful retention rates can be achieved with naltrexone, which may be improved by implants and particularly serial implants, repeat detoxification, meticulous clinical follow-up, and social support. As depot formulations of naltrexone become increasingly available such results can guide their clinical deployment, improve treatment outcomes, and enlarge the policy options for an exciting non-addictive pharmacotherapy for opiate addiction.

Mortality related to pharmacotherapies for opioid dependence: a comparative analysis of coronial records

INTRODUCTION AND AIMS

The aim of this study was to compare the mortality associated with oral naltrexone, methadone and buprenorphine in opioid dependence treatment, employing a retrospective data analysis using coronial and prescription data.

DESIGN AND METHODS

The number of deaths were identified through national coronial data and number of treatment recipients were estimated from 2000 to 2003 prescriptions and restricted medications data. Mortality rates were expressed as deaths per number of treatment episodes and per person-years at high and low risk of fatal opioid overdose.

RESULTS

Thirty-two oral naltrexone, one buprenorphine and 282 methadone-related deaths were identified. Mortality rates in the highest risk period in deaths per 100 person-years were 22.1 (14.6 - 32.2) for oral naltrexone following treatment cessation and 3.0 (2.3 - 3.9) for methadone during treatment induction. Rates in the lowest risk period in deaths per 100 person-years were 1.0 (0.3 - 2.2) during oral naltrexone treatment and 0.34 (0.3 - 0.4) during post-induction methadone treatment. The relative risk of death for oral naltrexone subjects was 7.4 times (high-risk period, p < 0.0001) or 2.8 times (low-risk period, p = 0.055) that of methadone subjects.

DISCUSSION AND CONCLUSIONS

This is the first comparison of mortality associated with these three pharmacotherapies for opioid dependence. The risk of death related to oral naltrexone appears higher than that related to methadone treatment.

Mortality in heroin users 3 years after naltrexone implant or methadone maintenance treatment

Concerns that treatment for heroin dependence using naltrexone may increase suicide rates during treatment and fatal overdoses posttreatment have been expressed. There is also disquiet about mortality during induction onto methadone. We assessed mortality during specific periods following treatment with naltrexone implants or methadone. Data were assembled using the Western Australian Data Linkage System. The methadone cohort comprised all those who started methadone in Western Australia during 2001-2002: The naltrexone cohort comprised all Western Australian heroin-dependent persons who received their first implant in 2001-2002. There were 15 (2.7%) deaths in the methadone cohort (n = 553) and 6 (1.8%) deaths in the naltrexone cohort (n = 341). Mortality rates for the "initial 14-day period," "stable treatment," and "overall" were 94.47, 0.0, and 5.83 deaths/1,000 person-years for the methadone group. In the naltrexone group, the rates "during first treatment (0-6 months)," "post first treatment," and overall were 0.0, 4.21, and 3.76 deaths/1,000 person-years. The age-standardized mortality rate ratio for naltrexone compared to methadone was 0.645 (95% confidence interval = 0.123-1.17). Increased mortality during induction onto methadone was confirmed. Evidence relating naltrexone to either increased suicide or overdose was not found. Overall mortality rates for naltrexone implant were similar to those for methadone, but increased mortality during methadone induction was avoided.

Effectiveness of low-dose naltrexone in the post-detoxification treatment of opioid dependence

BACKGROUND

The clinical use of naltrexone (NTX) in the treatment of opioid dependence has been limited because of poor compliance and inconsistent outcomes. In particular, the therapeutic benefit of extended treatment with NTX after opioid detoxification is unclear. The present study evaluated whether the augmentation with low-dose NTX during the post-detoxification treatment of opioid dependence would improve outcomes.

METHODS

In an open-label naturalistic design, 435 opioid-dependent patients who had completed inpatient detoxification were offered the choice of entering 1 of the 2 outpatient treatment arms: clonidine extended treatment (CET) (clonidine + psychosocial treatment), or enhanced extended treatment (EET) (oral NTX [1-10 mg/d] + CET) for 21 days. The primary outcome measure was retention in treatment. Secondary outcomes included abstinence from opioids, dropouts, and adherence to postdischarge care.

RESULTS

One hundred sixty-two patients (37.2%) accepted EET. Subjects receiving EET stayed longer in the program (F = 64.4; P = 0.000), were less likely to drop out, used less opioids, and followed through with referral to long-term outpatient treatment in a higher number, compared with patients in the CET arm (P = 0.000 in each case). The NTX + clonidine combination was safe and well tolerated.

CONCLUSIONS

This preliminary study indicates the potential benefit of augmentation with low-dose NTX to improve outcomes after opioid detoxification for a preferred group of patients. Randomized controlled trials are necessary to further evaluate the role of low-dose NTX in the outpatient treatment of opioid dependence.

Evidence for sugar addiction: behavioral and neurochemical effects of intermittent, excessive sugar intake

[Avena, N.M., Rada, P., Hoebel B.G., 2007. Evidence for sugar addiction: Behavioral and neurochemical effects of intermittent, excessive sugar intake. Neuroscience and Biobehavioral Reviews XX(X), XXX-XXX]. The experimental question is whether or not sugar can be a substance of abuse and lead to a natural form of addiction. "Food addiction" seems plausible because brain pathways that evolved to respond to natural rewards are also activated by addictive drugs. Sugar is noteworthy as a substance that releases opioids and dopamine and thus might be expected to have addictive potential. This review summarizes evidence of sugar dependence in an animal model. Four components of addiction are analyzed. "Bingeing," "withdrawal," "craving" and "cross-sensitization" are each given operational definitions and demonstrated behaviorally with sugar bingeing as the reinforcer. These behaviors are then related to neurochemical changes in the brain that also occur with addictive drugs. Neural adaptations include changes in dopamine and opioid receptor binding, enkephalin mRNA expression and dopamine and acetylcholine release in the nucleus accumbens. The evidence supports the hypothesis that under certain circumstances rats can become sugar dependent. This may translate to some human conditions as suggested by the literature on eating disorders and obesity.

Comparison of demographic and clinical characteristics between opioid-dependent individuals admitted to a community-based treatment setting and those enrolled in a research-based treatment setting

Despite the significant developments in pharmacotherapy and behavioral treatments for addiction, the dissemination of new treatment methods into the community has been slow. It has been pointed out that treatments developed in research settings may be impractical in community treatment settings, which might help explain the transition lag. Screening and recruitment of participants for research studies might partially explain this, as there is evidence that substance-abusing individuals who participate in clinical research are different on a number of measures from treatment seekers. However, no study has directly compared treatment seekers with research participants drawn from similar populations using prospective methods. This study compared the demographic characteristics, drug use and psychosocial problem severity levels, and personality traits of opioid-dependent individuals seeking help in a community setting (n = 502) with those of opioid-dependent individuals in a primarily research-based drug abuse treatment setting (n = 459); both settings offered a similar set of treatment services (opioid agonist medication and counseling). Although the overall findings revealed numerous similarities between the groups, differences were also observed. Most notably, there were significantly fewer women in the research sample than in the community-based treatment sample. Other differences included a modest but statistically significant increase in psychosocial problem severity levels in the community-based treatment sample and higher drug use problem severity levels in the research sample. Interestingly, many of these differences were strongest in women as compared with men.

Opioid maintenance: a comparative review of pharmacological strategies

The use of opioids outside of medical practice is a significant health problem with important social and political implications. Although treatment of opioid dependence is traditionally focused on heroin users, there is increasing recognition that a large number of people become dependent through the use of prescription opioids. The necessity for long-term treatment has also been increasingly recognised. At present, there are several pharmacotherapies available for maintenance treatment, including drugs that are full agonists at the opioid receptor (e.g., methadone, slow-release oral morphine), a partial agonist (buprenorphine) and an opioid antagonist (naltrexone). This review examines the existing strategies, highlights problems associated with their use and discusses the opportunities for new treatment approaches, particularly the use of long-acting formulations.

Analgesia and sedation in the presence of a naltrexone implant: a novel pharmacological challenge

In chronic opioid abusers, sedation and analgesia present challenges. We describe two trauma patients with naltrexone implants (depot micro-receptor antagonists that facilitate opioid withdrawal) requiring intensive care. The first patient, a 28-year-old man, sustained chest and pelvic injuries when hit by a motor vehicle. When we learned of the implant he was already on a morphine infusion, appearing responsive to it. It subsequently emerged that the implant was placed 3 months earlier, but had only a 6-week duration of effect and had expired. His intensive care course was unaffected. The second patient, a 24-year-old man, had been stabbed in the chest. His implant being recently placed, he was markedly opioid insensitive. Propofol, tramadol and paracetamol proved effective. We wish to notify colleagues of the existence of these implants as they are increasingly widely used, and should be considered when encountering severe opioid resistance. Secondly, their role in managing opioid-dependent physicians appears promising.

Research on naltrexone in the criminal justice system

Many parolees and probationers are opioid abusers, and substance abuse is a leading factor for the revocation of probation, parole, and other alternatives to incarceration. The opioid antagonist naltrexone would appear to be an excellent treatment for opioid abuse and dependence in this population and the authors sought to systematically review this literature. Using the PubMed database, the authors identified large bodies of criminal justice (CJS) and naltrexone literature. The search terms used in both searches were crosschecked to identify all articles that involved research on naltrexone in the CJS. Only two articles were identified. The lack of research on naltrexone in the criminal justice system highlights the need for more research on naltrexone in our overburdened CJS.

Sustained-release naltrexone formulations for the treatment of alcohol and opioid dependence

Naltrexone, an opioid receptor antagonist, is effective in the treatment of alcohol and opioid dependence. An important limitation of the use of oral naltrexone is the lack of efficacy among patients who do not consistently take the medication. The advent of a sustained-release naltrexone addresses the problem of noncompliance. Naltrexone can be compounded into microcapsules that can be injected or implanted, producing a clinical response lasting from 30 days to several months. Several randomized, placebo-controlled clinical trials demonstrate that sustained-release naltrexone is safe and effective for the treatment of both alcohol and opioid dependence. Sustained-release formulations of naltrexone may offer several advantages over its oral formulation with respect to medication compliance, pharmacokinetics, side effect profile and ease of use. Recently, one formulation of sustained-release naltrexone received approval from the US FDA and offers a new option for addiction treatment.

A systematic review of the effectiveness of naltrexone in the maintenance treatment of opioid and alcohol dependence

This systematic review summarises evidence of the effectiveness of naltrexone (NTX) and the added value of psychosocial treatment in the maintenance treatment of opioid and alcohol dependence. Studies were selected through a literature search conducted in March 2004. Seven opioid and seventeen alcohol studies were identified. When possible, meta-(regression) analyses were performed. There is lack of evidence about the effectiveness of NTX in the maintenance treatment of opioid dependence. There is evidence for the effectiveness and applicability of NTX in the management of alcohol dependence. The opioid studies combined NTX with a variety of psychosocial interventions, which plagued the evaluation of their value. Concomitant psychosocial interventions used in the alcohol studies were mainly cognitive behavioural, which seems to be more effective than NTX combined with supportive therapy. Available data do not allow firm conclusions regarding the added effect of psychosocial interventions. However, the data suggest that a combination of naltrexone with cognitive behavioural relapse prevention therapy is beneficial in alcohol dependent patients.

Opioid antagonists under heavy sedation or anaesthesia for opioid withdrawal

BACKGROUND

Withdrawal (detoxification) is necessary prior to drug-free treatment. It may also represent the end point of long-term opioid replacement treatment such as methadone maintenance. The availability of managed withdrawal is essential to an effective treatment system.

OBJECTIVES

To assess the effectiveness of interventions involving the administration of opioid antagonists to induce opioid withdrawal with concomitant heavy sedation or anaesthesia, in terms of withdrawal signs and symptoms, completion of treatment and adverse effects.

SEARCH STRATEGY

We searched the Drugs and Alcohol Group register (October 2003), Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 4, 2004), Medline (January 1966 to January 2005), Embase (January 1985 to January 2005), PsycINFO (1967 to January 2005), and Cinahl (1982 to December 2004) and reference lists of studies.

SELECTION CRITERIA

Controlled trials comparing antagonist-induced withdrawal under heavy sedation or anaesthesia with another form of treatment, or a different regime of anaesthesia-based antagonist-induced withdrawal.

DATA COLLECTION AND ANALYSIS

One reviewer assessed studies for inclusion and undertook data extraction and assessed quality. Inclusion decisions and the overall process were confirmed by consultation between all three reviewers.

MAIN RESULTS

Six studies (five randomised controlled trials) involving 834 participants met the inclusion criteria for the review.Antagonist-induced withdrawal is more intense but less prolonged than withdrawal managed with reducing doses of methadone, and doses of naltrexone sufficient for blockade of opioid effects can be established significantly more quickly with antagonist-induced withdrawal than withdrawal managed with clonidine and symptomatic medications. The level of sedation does not affect the intensity and duration of withdrawal, although the duration of anaesthesia may influence withdrawal severity. There is a significantly greater risk of adverse events with heavy, compared to light, sedation (RR 3.21, 95% CI 1.13 to 9.12, P = 0.03) and probably also other forms of detoxification.

AUTHORS' CONCLUSIONS

Heavy sedation compared to light sedation does not confer additional benefits in terms of less severe withdrawal or increased rates of commencement on naltrexone maintenance treatment. Given that the adverse events are potentially life-threatening, the value of antagonist-induced withdrawal under heavy sedation or anaesthesia is not supported. The high cost of anaesthesia-based approaches, both in monetary terms and use of scarce intensive care resources, suggest that this form of treatment should not be pursued.

A cost-effectiveness analysis of heroin detoxification methods in the Australian National Evaluation of Pharmacotherapies for Opioid Dependence (NEPOD)

This economic evaluation was part of the Australian National Evaluation of Pharmacotherapies for Opioid Dependence (NEPOD) project. Data from four trials of heroin detoxification methods, involving 365 participants, were pooled to enable a comprehensive comparison of the cost-effectiveness of five inpatient and outpatient detoxification methods. This study took the perspective of the treatment provider in assessing resource use and costs. Two short-term outcome measures were used-achievement of an initial 7-day period of abstinence, and entry into ongoing post-detoxification treatment. The mean costs of the various detoxification methods ranged widely, from AUD 491 dollars(buprenorphine-based outpatient); to AUD 605 dollars for conventional outpatient; AUD 1404 dollars for conventional inpatient; AUD 1990 dollars for rapid detoxification under sedation; and to AUD 2689 dollars for anaesthesia per episode. An incremental cost-effectiveness analysis was carried out using conventional outpatient detoxification as the base comparator. The buprenorphine-based outpatient detoxification method was found to be the most cost-effective method overall, and rapid opioid detoxification under sedation was the most cost-effective inpatient method.

A new approach to preventing relapse in opiate addicts: A psychometric evaluation

The present study investigated psychological aspects after different methods of withdrawal treatments in opiate addicts had been conducted. Two pharmacological strategies based on delivering an opioid agonist or antagonist were used for withdrawal in opiate addicts. After detoxification, the antagonist was delivered by a pellet implanted subcutaneously. Four days after the beginning of the treatment several psychological variables such as craving, anxiety, depression, and mood were assessed and compared with data from actively consuming opiate addicts and healthy controls. In addition, 6 and 12 weeks later the relapse rates were assessed. Compared with addicts detoxified and treated with Levomethadone as well as actively heroin consuming addicts, subjects treated with Naltrexone demonstrated significantly higher positive psychological outcome concerning all assessed variables and significantly lower relapse rates. Naltrexone implants prove prevention of relapse during the most vulnerable period after detoxification. Compared with Levomethadone withdrawal, they lead to a significantly better psychological condition in patients.

Naltrexone implants -- duration, tolerability and clinical usefulness. A pilot study

Naltrexone blocks opioid effects effectively, but poor compliance limits the clinical usefulness in the treatment of opioid dependence. Long-acting implanted formulations might increase the clinical feasibility. Several implants have been produced, but few clinical reports have been published. This paper describes an open trial with an Australian implant. This implant is claimed to have duration of up to six months with double implants and acceptable levels of side effects. This was explored in the present pilot study with 13 opioid-dependent patients. By single implant of 1.8 g naltrexone the duration judged by naltrexone plasma levels above 1 ng/ml naltrexone was between 2 and 4 months. Double implants maintained such plasma levels for 5-6.5 months. Clinically, the implants appeared promising. Side effects were minimal. During the period with adequate plasma levels of naltrexone, use of opioids was absent and use of other psychoactive drugs reduced. At 1-year follow-up, the patients rated the implants highly positively.

Constitutive opioid receptor activation: a prerequisite mechanism involved in acute opioid withdrawal

The opioid receptor antagonist naltrexone, which is used in detoxification and rehabilitation programmes in opioid addicts, can precipitate opioid withdrawal symptoms even in patients who have no opioid present. We tested the hypothesis that in order to precipitate withdrawal, opioids need to convert the inactive opioid receptor site via protein kinase C into a constitutively active form on which the antagonist precipitates withdrawal. Acute microg/kg), given for 6 days, which was followed by the antagonist naltrexone (20 microg/kg i.v.) in the awake trained canine (n = 10). Abrupt displacement of opioid binding resulted in acute withdrawal symptoms: increase in blood pressure, heart rate, increase in amplitude height of somatosensory evoked potential, reduced tolerance to colon distention and a significant increase in grading of vegetative variables (restlessness, panting, thrashing of the head, whining, yawning, gnawing, salivation and/or rhinorrhoea, mydriasis, stepping of extremities and vomiting). Following a washout period of 14 days, the same animals were given the highly specific protein kinase C inhibitor H7 (250 microg/kg) prior to the same dosages of sufentanil and naltrexone. Such pretreatment was able to either attenuate or completely abolish the acute withdrawal symptoms. The data suggest that for precipitation of withdrawal, intracellular phosphorylation is a prerequisite in order to activate the opioid mu-receptor. In such a setting, naltrexone acts like an 'inverse agonist' relative to the action of the antagonist on a non-preoccupied receptor site not being exposed previously to a potent opioid agonist.

Chronic Pain and Ultrarapid Opioid Detoxification

Availability of opiate substances through physicians and on the street has led to a rise in dependence and in addiction resulting in countless numbers of people hooked on these drugs. Long-term use of these agents results in reduction of endogenous supply of opiate replaced by these exogenous compounds. A technique known as Ultrarapid Detoxification (UROD) has been developed and appears more promising than conventional modalities. UROD has been modified over 3 decades resulting in a safe and an effective general anesthetic that results in hemodynamically stable withdrawal without manifestation of central nervous system hyperarousal. A cornerstone of this technique involves clonidine, which stimulates reuptake of catecholamines and allows for large doses of opioid antagonist to be delivered without significant changes in heart rate or blood pressure, displacing the opiate. Though techniques vary from center to center, safety should be paramount with the technique performed in an intensive care unit with trained professional anesthesiologists. Psychosocial issues should be evaluated by a trained addictionalist and most people will succeed from the UROD procedure without experiencing the horrible withdrawal syndrome. Patients must have realistic goals and be prepared to deal with psychosocial issues post-procedure.

Endogenous opiates and behavior: 2003

This paper is the 26th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2003 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).