Self-administration of intravenous buprenorphine and the buprenorphine/naloxone combination by recently detoxified heroin abusers

Buprenorphine/naloxone - one formulation that doesn't fit all: a case report

BACKGROUND

Sublingual buprenorphine, approved for treatment of opioid use disorder since 2002, is most commonly available in co-formulation with naloxone. Naloxone is an opioid antagonist minimally absorbed when sublingual (SL) buprenorphine/naloxone is taken as prescribed; it is thought to reduce potential for misuse via intravenous administration. However, growing data and clinical experience demonstrate that previously accepted assumptions about the pharmacokinetics of these medications may not apply to all patients.

CASE PRESENTATION

We present a patient whose adverse post-administration side effects on SL buprenorphine/naloxone resolved with transition to SL buprenorphine monoproduct.

DISCUSSION

Naloxone can be detected in nearly all patients taking SL buprenorphine/naloxone, though with apparent variability in clinical effect. In a minority of patients, naloxone can contribute to adverse and potentially treatment-limiting side effects. Furthermore, the naloxone component is commonly misunderstood by patients and providers and can foster mistrust in the therapeutic relationship if providers are perceived to be withholding a more tolerable formulation. Prescribers should have a low threshold to offer buprenorphine alone when clinically appropriate.

Patterns of use and adverse events reported among persons who regularly inject buprenorphine: a systematic review

BACKGROUND AND AIMS

Given the ongoing opioid crisis, novel interventions to treat severe opioid use disorder (OUD) are urgently needed. Injectable opioid agonist therapy (iOAT) with diacetylmorphine or hydromorphone is effective for the treatment of severe, treatment-refractory OUD, however barriers to implementation persist. Intravenous buprenorphine for the treatment of OUD (BUP iOAT) has several possible advantages over traditional iOAT, including a safety profile that might enable take-home dosing. We aimed to characterize injecting practices among real-world populations of persons who regularly inject buprenorphine, as well as associated adverse events reported in order to inform a possible future BUP iOAT intervention.

METHODS

We conducted a systematic review. We searched MEDLINE, EMBASE, and PsycINFO from inception through July 2020 and used backwards citation screening to search for publications reporting on dose, frequency among persons who regularly inject the drug, or adverse events associated with intravenous use of buprenorphine. The review was limited to English language publications and there was no limitation on study type. Study quality and risk of bias was assessed using the Mixed Methods Appraisal Tool. Narrative synthesis was used in reporting the results.

RESULTS

Eighty-eight studies were included in our review. Regular injection of buprenorphine was identified across diverse settings world-wide. Daily dose of oral buprenorphine injected was < 1-12 mg. Frequency of injection was 0-10 times daily. Adverse events could be characterized as known side effects of opioids/buprenorphine or injection-related complications. Most studies were deemed to be of low quality.

CONCLUSIONS

Extramedical, intravenous use of buprenorphine, continues to be documented. BUP iOAT may be feasible and results may inform the development of a study to test the efficacy and safety of such an intervention. Future work should also examine acceptability among people with severe OUD in North America. Our review was limited by the quality of included studies.

Buprenorphine abuse and health risks in Iran: A systematic review

INTRODUCTION

Buprenorphine maintenance treatment (BMT) is widely used in Iran, and its use is growing continuously. We reviewed studies on buprenorphine use, non-prescribed use, use disorder and treatment-seeking for it, buprenorphine-associated poisoning, and mortality in Iran in the current systematic review.

METHODS

An Iranian database (Scientific Information Database; SID) and three International electronic databases (PubMed, Scopus, and Web of Science) were searched for publications up to August 2020 for the relevant data. Opportunistic methods (Contact with experts and backward citation tracking) were also used for this purpose. Identified records were screened for eligibility criteria, and data of included studies were extracted. For context, the trend of BMT in the country was also examined.

RESULTS

Ten studies were found on the prevalence of non-prescribed buprenorphine use, seven were on the regular use and use disorder, and two studies on buprenorphine poisoning. The last 12-month prevalence of non-prescribed use was lower than 0.5 % in the general population, university, and high school students. The indicator was 2.5 % among persons who use drugs in a 2018 national study. The proportion of buprenorphine poisoning was 4.9 % among all illicit substance poisoning cases admitted to a hospital. The proportion of buprenorphine poisoning cases among all acute pediatric drug poisoning cases increased from 1.2 % to 2.5 % in a 3-year study.

CONCLUSION

Despite the expansion of BMT in Iran in the last decade, the adverse health consequences associated with buprenorphine are infrequent, when compared to other opioids used in Iran, suggesting the safety of BMT for future expansion.

Non-Opioid Treatments for Opioid Use Disorder: Rationales and Data to Date

Opioid use disorder (OUD) represents a major public health problem that affects millions of people in the USA and worldwide. The relapsing and recurring aspect of OUD, driven by lasting neurobiological adaptations at different reward centres in the brain, represents a major obstacle towards successful long-term remission from opioid use. Currently, three drugs that modulate the function of the opioidergic receptors, methadone, buprenorphine and naltrexone have been approved by the US Food and Drug Administration (FDA) to treat OUD. In this review, we discuss the limitations and challenges associated with the current maintenance and medication-assisted withdrawal strategies commonly used to treat OUD. We further explore the involvement of glutamatergic, endocannabinoid and orexin signaling systems in the development, maintenance and expression of addiction-like behaviours in animal models of opioid addiction, and as potential and novel targets to expand therapeutic options to treat OUD. Despite a growing preclinical literature highlighting the role of these potential targets in animal models of opioid addiction, clinical and translational studies for novel treatments of OUD remain limited and inconclusive. Further preclinical and clinical investigations are needed to expand the arsenal of primary treatment options and adjuncts to maximise efficacy and prevent relapse.

Buprenorphine Pharmacology Review: Update on Transmucosal and Long-acting Formulations

: Buprenorphine is an effective treatment for opioid use disorder. As a high-affinity, partial agonist for the mu-opioid receptor, buprenorphine suppresses opioid withdrawal and craving, reduces illicit opioid use, and blocks exogenous opioid effects including respiratory depression. Other pharmacologic benefits of buprenorphine are its superior safety profile compared with full opioid agonists and its long half-life that allows daily or less-than-daily dosing. New and innovative buprenorphine formulations, with pharmacokinetic profiles that differ from the original tablet formulation, continue to be developed. These include higher bioavailability transmucosal tablets and films and also 6-month implantable and monthly injectable products. This growing array of available formulations allows more choices for patients and increased opportunity for clinicians to individualize treatment; thus, it is important for buprenorphine prescribers to understand these differences.

Buprenorphine: prospective novel therapy for depression and PTSD

BACKGROUND

Depression and post-traumatic stress disorder (PTSD) are leading causes of disability and loss of life by suicide. Currently, there are less than satisfactory medical solutions to treat these mental disorders. Here, we explore recent preclinical and clinical studies demonstrating the potential of using buprenorphine to treat major depressive disorder, treatment-resistant depression, and PTSD.

METHOD

Bibliographic databases were searched to include preclinical and clinical studies demonstrating the therapeutic potential of buprenorphine and the involvement of the kappa opioid receptor (KOR) in mediating these effects.

RESULTS

Original clinical studies examining the effectiveness of buprenorphine to treat depression were mixed. The majority of participants in the PTSD studies were males and suffer from chronic pain and/or substance use disorders. Nonetheless, these recent studies and analyses established proof of concept warranting farther investigations. Additionally, KOR likely mediates the antidepressant and some of the anxiolytic effects of buprenorphine. Still, it appears that the full spectrum of buprenorphine's beneficial effects might be due to activity at other opioid receptors as well.

CONCLUSIONS

Pharmaceuticals' abilities to treat medical conditions directly relates to their ability to act upon the endogenous biological systems related to the conditions. Thus, these recent findings are likely a reflection of the central role that the endogenous opioid system has in these mental illnesses. Further studies are necessary to study the involvement of endogenous opioid systems, and specifically KOR, in mediating buprenorphine's beneficial effects and the ability to treat these medical conditions while minimizing risks for misuse and diversion.

Characterization of diverted buprenorphine use among adults entering corrections-based drug treatment in Kentucky

BACKGROUND

Illicit, medically unsupervised use of buprenorphine (i.e., "diverted use") among vulnerable and underserved populations, such as corrections-involved adults, remains underexplored.

METHODS

Survey data (2016-2017) collected as part of a clinical assessment of incarcerated adults entering corrections-based substance use treatment in Kentucky were analyzed. For years examined, 12,915 completed the survey. Removing cases for participants who did not reside in Kentucky for >6 months during the one-year pre-incarceration period (n = 908) resulted in a final sample size of 12,007.

RESULTS

Over a quarter of the sample reported past-year diverted buprenorphine use prior to incarceration and 21.8 % reported use during the 30-days prior to incarceration, using 6.5 months and 14.3 days on average, respectively. A greater proportion of participants who reported diverted buprenorphine use had previously been engaged with some substance use treatment (77.0 %) and reported greater perceived need for treatment (79.4 %) compared to those who did not report use. Use was more likely among participants who were younger, white, male, and who reported rural or Appalachian residence. Diverted buprenorphine users also evidenced extensive polydrug use and presented with greater substance use disorder severity. Non-medical prescription opioid, heroin, and diverted methadone use were associated with increased odds of diverted buprenorphine use while kratom was not. Diverted methadone use was associated with a 252.9 % increased likelihood of diverted buprenorphine use.

CONCLUSIONS

Diverted buprenorphine use among participants in this sample was associated with concerning high-risk behaviors and may indicate barriers to accessing opioid agonist therapies for corrections-involved Kentucky residents, particularly those in rural Appalachia.

Progress in agonist therapy for substance use disorders: Lessons learned from methadone and buprenorphine

Substance use disorders (SUD) are serious public health problems worldwide. Although significant progress has been made in understanding the neurobiology of drug reward and the transition to addiction, effective pharmacotherapies for SUD remain limited and a majority of drug users relapse even after a period of treatment. The United States Food and Drug Administration (FDA) has approved several medications for opioid, nicotine, and alcohol use disorders, whereas none are approved for the treatment of cocaine or other psychostimulant use disorders. The medications approved by the FDA for the treatment of SUD can be divided into two major classes - agonist replacement therapies, such as methadone and buprenorphine for opioid use disorders (OUD), nicotine replacement therapy (NRT) and varenicline for nicotine use disorders (NUD), and antagonist therapies, such as naloxone for opioid overdose and naltrexone for promoting abstinence. In the present review, we primarily focus on the pharmacological rationale of agonist replacement strategies in treatment of opioid dependence, and the potential translation of this rationale to new therapies for cocaine use disorders. We begin by describing the neural mechanisms underlying opioid reward, followed by preclinical and clinical findings supporting the utility of agonist therapies in the treatment of OUD. We then discuss recent progress of agonist therapies for cocaine use disorders based on lessons learned from methadone and buprenorphine. We contend that future studies should identify agonist pharmacotherapies that can facilitate abstinence in patients who are motivated to quit their illicit drug use. Focusing on those that are able to achieve abstinence from cocaine will provide a platform to broaden the effectiveness of medication and psychosocial treatment strategies for this underserved population. This article is part of the Special Issue entitled 'New Vistas in Opioid Pharmacology'.

Development of vaccines to treat opioid use disorders and reduce incidence of overdose

Vaccines offer a promising therapeutic strategy to treat substance use disorders (SUD). Vaccines have shown extensive preclinical proof of selectivity, safety, and efficacy against opioids, nicotine, cocaine, methamphetamine, and designer drugs. Despite clinical evaluation of vaccines targeting nicotine and cocaine showing proof of concept for this approach, no vaccine for SUD has yet reached the market. This review first discusses how vaccines for treatment of opioid use disorders (OUD) and reduction of opioid-induced fatal overdoses fit within the current medication assisted treatment (MAT) portfolio, and then summarizes ongoing efforts toward translation of vaccines targeting heroin, oxycodone, fentanyl, and other opioids. This article is part of the Special Issue entitled 'New Vistas in Opioid Pharmacology'.

Descriptive, observational study of pharmaceutical and non-pharmaceutical arrests, use, and overdoses in Maine

OBJECTIVES

The Maine Diversion Alert Program grants healthcare providers access to law enforcement data on drug charges. The objectives of this report were to analyse variations in drug charges by demographics and examine recent trends in arrests, prescriptions of controlled substances and overdoses.

DESIGN

Observational.

SETTING

Arrests, controlled prescription medication distribution and overdoses in Maine.

PARTICIPANTS

Drug arrestees (n=1272) and decedents (n=2432).

PRIMARY OUTCOME MEASURES

Arrestees were analysed by sex and age. Substances involved in arrests were reported by schedule (I-V or non-controlled prescription) and into opioids, stimulants or other classes. Controlled substances reported to the Drug Enforcement Administration (2007-2017) were evaluated. Drug-induced deaths (2007-2017) reported to the medical examiner were examined by the substance(s) identified.

RESULTS

Males were more commonly arrested for stimulants and schedule II substances. More than two-thirds of arrests involved individuals under the age of 40. Individuals age >60 were elevated for oxycodone arrests. Over three-fifths (63.38%) of arrests involved schedule II-IV substances. Opioids accounted for almost half (44.6%) of arrests followed by stimulants (32.5%) and sedatives (9.1%). Arrests involving buprenorphine exceeded those for oxycodone, hydrocodone, methadone, tramadol and morphine, combined. Prescriptions for hydrocodone (-56.0%) and oxycodone (-46.9%) declined while buprenorphine increased (+58.1%) between 2012 and 2017. Deaths from 2007 to 2017 tripled. Acetylfentanyl and furanylfentanyl were the most common fentanyl analogues identified.

CONCLUSIONS

Although the overall profile of those arrested for drug crimes in 2017 involve males, age <40 and heroin, exceptions (oxycodone for older adults) were observed. Most prescription opioids are decreasing while deaths involving opioids continue to increase in Maine.

Demystifying buprenorphine misuse: Has fear of diversion gotten in the way of addressing the opioid crisis?

Buprenorphine is considered one of the most effective treatments for opioid use disorder and significantly reduces risk of overdose death. However, concerns about its diversion and misuse have often taken center stage in public discourse and in the design of practices and policies regarding its use. This has been to the detriment of many vulnerable patient populations, especially those involved in the criminal justice system. Policies that restrict access to buprenorphine in criminal justice and other settings due to concerns of diversion do not accurately reflect the relative risks and safety profile associated with it, creating unnecessary barriers that drive an illicit market of this much-needed medication. Although proper regulation of all controlled medications should be a priority, in most instances the benefits of buprenorphine highly outweigh its risks. In the midst of a national crisis, efforts should be focused on expanding, and not restricting, access to this lifesaving treatment.

Buprenorphine prescription, misuse and service provision: a global perspective

Buprenorphine, a partial μ-opioid agonist and κ-opioid antagonist, is recommended as safe and effective maintenance treatment for opioid dependence. It offers the possibility of management in primary care settings. However, its prescription has led to diversion for illicit recreational use and resulted in medical complications and, rarely, fatal overdose in combination with other sedatives. The outcome of buprenorphine maintenance programmes varies from country to country and it is determined by the local therapeutic traditions, regulatory restrictions and existing service provision for opioid misusers. This article addresses the pharmacology of buprenorphine, the benefits and drawbacks of its prescription, service provision for opioid misuse around the world, policy recommendations, and prescribing training requirements.

Clinical models of decision making in addiction

As research on decision making in addiction accumulates, it is increasingly clear that decision-making processes are dysfunctional in addiction and that this dysfunction may be fundamental to the initiation and maintenance of addictive behavior. How drug-dependent individuals value and choose among drug and nondrug rewards is consistently different from non-dependent individuals. The present review focuses on the assessment of decision-making in addiction. We cover the common behavioral tasks that have shown to be fruitful in decision-making research and highlight analytical and graphical considerations, when available, to facilitate comparisons within and among studies. Delay discounting tasks, drug demand tasks, drug choice tasks, the Iowa Gambling Task, and the Balloon Analogue Risk Task are included.

Efficacy and tolerability of buccal buprenorphine in opioid-experienced patients with moderate to severe chronic low back pain: results of a phase 3, enriched enrollment, randomized withdrawal study

Supplemental Digital Content is Available in the Text.

In opioid-experienced patients (30-160 mg MSE/d), buccal buprenorphine was superior to placebo in 30%-50% pain reductions and PGIC, with similar constipation incidence.

A buccal film of buprenorphine (BBUP) was evaluated for safety and efficacy in a multicenter, double-blind, placebo-controlled, enriched-enrollment, randomized-withdrawal study in opioid-experienced patients (30 to ≤160 mg/d morphine sulfate equivalent) with moderate to severe chronic low back pain taking around-the-clock opioid analgesics. Patients' opioid doses were tapered to ≤30 mg morphine sulfate equivalent before open-label titration with BBUP (range, 150-900 μg every 12 hours). Patients who responded (received adequate analgesia that was generally well tolerated for 14 days) were randomized to receive buprenorphine (n = 254) or placebo (n = 257) buccal film. The primary efficacy variable was the change from baseline to week 12 of double-blind treatment in mean average daily pain-intensity scores using a rating scale of 0 (no pain) to 10 (worst pain imaginable). In the intent-to-treat population, mean pain scores were 6.7 after opioid taper and declined to 2.8 after the BBUP titration period. After randomization, mean pain scores were lower in the BBUP group than in the placebo group; the difference between groups in the mean change from baseline to week 12 was −0.98 (95% CI, −1.32 to −0.64; P < 0.001). A significantly larger percentage of patients receiving BBUP than placebo had pain reductions ≥30% and ≥50% (P < 0.001 for both). In the double-blind portion of the study, the only adverse event reported more frequently with BBUP than placebo and in ≥5% of patients was vomiting (5.5% vs 2.3%). These findings demonstrate the efficacy and tolerability of BBUP in opioid-experienced patients taking around-the-clock opioid treatment for chronic low back pain.

Abuse liability of intravenous buprenorphine vs. buprenorphine/naloxone: Importance of absolute naloxone amount

BACKGROUND

This study sought to determine the relative importance of a range of Bup/Nx doses compared to Bup alone in producing subjective and reinforcing effects.

METHODS

Heroin-using volunteers (n=13) were transitioned onto daily oral hydromorphone (40mg). Laboratory sessions assessed the reinforcing and subjective effects of intravenous (IV) doses of Bup (1.51, 2.16, 6.15, and 8.64mg) and Bup/Nx (1.51/0.44, 2.16/0.61, 6.15/1.71, and 8.64/2.44mg). Placebo (Pbo), heroin (25mg) and Nx (0.3mg) were tested as neutral, positive, and negative controls, respectively.

RESULTS

IV Bup alone was self-administered substantially less than IV heroin, though the two largest doses of Bup produced positive subjective effects, drug "Liking" (0-100mm), which were comparable to heroin (mean difference: Heroin vs Bup 6.15mg: -3.4mm, Heroin vs Bup 8.64mg: -11.3mm). All indicators of abuse potential seen with IV Bup alone were substantially decreased with the addition of Nx. All Bup/Nx combinations produced ratings of aversive effects, "Bad", which were comparable to, or greater than IV, Nx. On three of the four measures of aversive effects, the largest difference is seen with the 8.64 vs 8.64/2.44 condition.

CONCLUSIONS

This study further demonstrates the ability of the Bup/Nx combination to deter IV use. Although none of the Bup/Nx combinations showed indications of abuse potential, formulations with larger absolute Nx, may be less abusable as they precipitate a greater degree of withdrawal.

Effect of Buprenorphine Weekly Depot (CAM2038) and Hydromorphone Blockade in Individuals With Opioid Use Disorder: A Randomized Clinical Trial

IMPORTANCE

Buprenorphine is an efficacious, widely used treatment for opioid use disorder (OUD). Daily oral transmucosal formulations can be associated with misuse, diversion, and nonadherence; these limitations may be obviated by a sustained release formulation.

OBJECTIVE

To evaluate the ability of a novel, weekly, subcutaneous buprenorphine depot formulation, CAM2038, to block euphorigenic opioid effects and suppress opioid withdrawal in non-treatment-seeking individuals with OUD.

DESIGN, SETTING, AND PARTICIPANTS

This multisite, double-blind, randomized within-patient study was conducted at 3 controlled inpatient research facilities. It involved 47 adults with DSM-V moderate-to-severe OUD. The study was conducted from October 12, 2015 (first patient enrolled), to April 21, 2016 (last patient visit).

INTERVENTIONS

A total of five 3-day test sessions evaluated the response to hydromorphone (0, 6, and 18 mg intramuscular in random order; 1 dose/session/day). After the first 3-day session (ie, qualification phase), participants were randomized to either CAM2038 weekly at 24 mg (n = 22) or 32 mg (n = 25); the assigned CAM2038 dose was given twice, 1 week apart (day 0 and 7). Four sets of sessions were conducted after randomization (days 1-3, 4-6, 8-10, and 11-13).

MAIN OUTCOMES AND MEASURES

The primary end point was maximum rating on the visual analog scale for drug liking. Secondary end points included other visual analog scale (eg, high and desire to use), opioid withdrawal scales, and physiological and pharmacokinetic outcomes.

RESULTS

A total of 46 of 47 randomized participants (mean [SD] age, 35.5 [9] years; 76% male [n = 35]) completed the study. Both weekly CAM2038 doses produced immediate and sustained blockade of hydromorphone effects (liking maximum effect, CAM2038, 24 mg: effect size, 0.813; P < .001, and CAM2038, 32 mg: effect size, 0.753; P < .001) and suppression of withdrawal (Clinical Opiate Withdrawal Scale, CAM2038, 24 mg: effect size, 0.617; P < .001, and CAM2038, 32 mg: effect size, 0.751; P < .001). CAM2038 produces a rapid initial rise of buprenorphine in plasma with maximum concentration around 24 hours, with an apparent half-life of 4 to 5 days and approximately 50% accumulation of trough concentration from first to second dose (trough concentration = 0.822 and 1.23 ng/mL for weeks 1 and 2, respectively, with 24 mg; trough concentration = 0.993 and 1.47 ng/mL for weeks 1 and 2, respectively, with 32 mg).

CONCLUSIONS AND RELEVANCE

CAM2038 weekly, 24 and 32 mg, was safely tolerated and produced immediate and sustained opioid blockade and withdrawal suppression. The results support the use of this depot formulation for treatment initiation and stabilization of patients with OUD, with the further benefit of obviating the risk for misuse and diversion of daily buprenorphine while retaining its therapeutic benefits.

TRIAL REGISTRATION

Clinicaltrials.gov Identifier: NCT02611752.

Abuse potential of intranasal buprenorphine versus buprenorphine/naloxone in buprenorphine-maintained heroin users

In spite of the clinical utility of buprenorphine, parenteral abuse of this medication has been reported in several laboratory investigations and in the real world. Studies have demonstrated lower abuse liability of the buprenorphine/naloxone combination relative to buprenorphine alone. However, clinical research has not yet examined the utility of the combined formulation to deter intranasal use in a buprenorphine-maintained population. Heroin-using volunteers (n = 12) lived in the hospital for 8-9 weeks and were maintained on each of three sublingual buprenorphine doses (2, 8, 24 mg). Under each maintenance dose, participants completed laboratory sessions during which the reinforcing and subjective effects of intranasal doses of buprenorphine (8, 16 mg), buprenorphine/naloxone (8/2, 8/8, 8/16, 16/4 mg) and controls (placebo, heroin 100 mg, naloxone 4 mg) were assessed. Intranasal buprenorphine alone typically produced increases in positive subjective effects and the 8 mg dose was self-administered above the level of placebo. The addition of naloxone dose dependently reduced positive subjective effects and increased aversive effects. No buprenorphine/naloxone combination dose was self-administered significantly more than placebo. These data suggest that within a buprenorphine-dependent population, intranasal buprenorphine/naloxone has reduced abuse potential in comparison to buprenorphine alone. These data strongly argue in favor of buprenorphine/naloxone rather than buprenorphine alone as the more reasonable option for managing the risk of buprenorphine misuse.

The reinforcing and subjective effects of intravenous and intranasal buprenorphine in heroin users

Abuse of buprenorphine (BUP) by the intravenous (IV) route has been documented in several studies, and reports of intranasal (IN) abuse are increasing. However, no studies have directly compared the effects of BUP when it is administered intranasally and intravenously. The present secondary analysis used data from two separate studies to compare the reinforcing and subjective effects of IV and IN buprenorphine. One study evaluated IV buprenorphine (N=13) and the other evaluated IN buprenorphine (N=12). Participants were maintained on 2 mg sublingual (SL) BUP and tested with each intranasal or intravenous buprenorphine test dose (0 mg, 2 mg, 4 mg, 8 mg, and 16 mg). During morning laboratory sessions, participants received money (US $20) and sample doses of IN or IV BUP, and then completed subjective effects questionnaires. Later that day, they completed a self-administration task to receive 10% portions of the drug and/or money they previously sampled. In general, positive subjective ratings for both IV and IN BUP were significantly greater than placebo, with IV BUP having a greater effect than IN BUP. All active BUP doses (IV and IN) maintained significantly higher progressive ratio breakpoint values than placebo, but breakpoint values for IV BUP were greater than for IN BUP. Buprenorphine is an effective maintenance treatment for opioid dependence, valued for its ability to reduce the positive subjective effects of other opioids. Nevertheless, the present data demonstrate that in participants maintained on a low dose of SL BUP, the medication itself has abuse liability when used intravenously or intranasally.

Abuse and diversion of buprenorphine sublingual tablets and film

Buprenorphine abuse is common worldwide. Rates of abuse and diversion of three sublingual buprenorphine formulations (single ingredient tablets; naloxone combination tablets and film) were compared. Data were obtained from the Researched Abuse, Diversion, and Addiction-Related Surveillance (RADARS) System Poison Center, Drug Diversion, Opioid Treatment (OTP), Survey of Key Informants' Patients (SKIP), and College Survey Programs through December 2012. To control for drug availability, event ratios (rates) were calculated quarterly, based on the number of patients filling prescriptions for each formulation ("unique recipients of a dispensed drug," URDD) and averaged and compared using negative binomial regression. Abuse rates in the OTP, SKIP, and College Survey Programs were greatest for single ingredient tablets, and abuse rates in the Poison Center Program and illicit diversion rates were greatest for the combination tablets. Combination film rates were significantly less than rates for either tablet formulation in all programs. No geographic pattern could be discerned.

Methadone and buprenorphine-naloxone are effective in reducing illicit buprenorphine and other opioid use, and reducing HIV risk behavior--outcomes of a randomized trial

AIMS

Determine the extent to which buprenorphine injectors continue treatment with buprenorphine-naloxone or methadone, and the impact of these treatments on substance use and HIV risk in the Republic of Georgia.

METHODS

Randomized controlled 12-week trial of daily-observed methadone or buprenorphine-naloxone followed by a dose taper, referral to ongoing treatment, and follow-up at week 20 at the Uranti Clinic in Tbilisi, Republic of Georgia. Eighty consenting treatment-seeking individuals (40/group) aged 25 and above who met ICD-10 criteria for opioid dependence with physiologic features and reported injecting buprenorphine 10 or more times in the past 30 days. Opioid use according to urine tests and self-reports, treatment retention, and HIV risk behavior as determined by the Risk Assessment Battery.

RESULTS

Mean age of participants was 33.7 (SD5.7), 4 were female, mean history of opioid injection use was 5.8 years (SD4.6), none were HIV+ at intake or at the 12-week assessment and 73.4% were HCV+. Sixty-eight participants (85%) completed the 12-week medication phase (33 from methadone and 35 from buprenorphine/naloxone group); 37 (46%) were in treatment at the 20-week follow-up (21 from methadone and 16 from the buprenorphine/naloxone group). In both study arms, treatment resulted in a marked reduction in unprescribed buprenorphine, other opioid use, and HIV injecting risk behavior with no clinically significant differences between the two treatment arms.

CONCLUSIONS

Daily observed methadone or buprenorphine-naloxone are effective treatments for non-medical buprenorphine and other opioid use in the Republic of Georgia and likely to be useful for preventing HIV infection.

Comparison of a drug versus money and drug versus drug self-administration choice procedure with oxycodone and morphine in opioid addicts

This double-blind, placebo-controlled study investigated the effects of oral morphine (0, 45, 135 mg/70 kg) and oral oxycodone (0, 15, 45 mg/70 kg) on buprenorphine-maintained opioid addicts. As a 3: 1 morphine : oxycodone oral dose ratio yielded equivalent subjective and physiological effects in nondependent individuals, this ratio was used in the present study. Two self-administration laboratory procedures - that is, a drug versus money and a drug versus drug procedure - were assessed. Study participants (N=12) lived in the hospital and were maintained on 4 mg/day sublingual buprenorphine. When participants chose between drug and money, money was preferred over all drug doses; only high-dose oxycodone was self-administered more than placebo. When participants chose between drug and drug, both drugs were chosen more than placebo, high doses of each drug were chosen over low doses, and high-dose oxycodone was preferred over high-dose morphine. The subjective, performance-impairing, and miotic effects of high-dose oxycodone were generally greater than those of high-dose morphine. The study demonstrated that a 3: 1 oral dose ratio of morphine : oxycodone was not equipotent in buprenorphine-dependent individuals. Both self-administration procedures were effective for assessing the relative reinforcing effects of drugs; preference for one procedure should be driven by the specific research question of interest.

A review of human drug self-administration procedures

Drug self-administration procedures in laboratory settings allow us to closely model drug-taking behavior in real-world settings. This review provides an overview of many of the common self-administration methods used in human laboratory research. Typically, self-administration studies provide a quantifiable measure of the reinforcing effect of a drug, which is believed to be predictive of its potential for abuse. Several adaptations of the self-administration paradigm exist, the simplest of which allows participants free access to the drug under investigation. Free-access procedures allow investigators to observe patterns of drug self-administration and drug effects in a controlled setting. Allowing participants to choose between two simultaneously available reinforcers (choice procedures) is another well-established method of assessing the reinforcing effects of a drug. Offering a choice between two reinforcers (e.g. two different doses of the same drug, two different drugs, or drug and nondrug reinforcers) provides researchers with a point of comparison (e.g. between a drug of known abuse potential and a novel drug). When combined with other endpoints, such as subjective effects ratings, physiological responses, and cognitive performance, human self-administration paradigms have contributed significantly to our understanding of the factors that contribute to, maintain, and alter drug-taking behavior including: craving, positive subjective effects, toxicity, drug interactions and abstinence. This area of research has also begun to incorporate other techniques such as imaging and genetics to further understand the multifaceted nature of substance abuse. The present paper summarizes the different self-administration techniques that are commonly used today and the application of other procedures that may complement interpretation of the drug self-administration findings.

Inability to access buprenorphine treatment as a risk factor for using diverted buprenorphine

BACKGROUND

As buprenorphine prescribing has increased in the United States so have reports of its diversion. The study purpose was to examine frequency and source of and risk factors for diverted buprenorphine use over a 6-month period in an Appalachian community sample of prescription opioid abusers.

METHODS

There were 503 participants at baseline; 471 completed the 6-month follow-up assessment. Psychiatric disorders and demographic, drug use, and social network characteristics were ascertained at baseline and follow-up. Multivariable logistic regression was used to determine the predictors of diverted buprenorphine use over the 6-month period.

RESULTS

Lifetime buprenorphine use "to get high" was 70.1%. Nearly half (46.5%) used diverted buprenorphine over the 6-month follow-up period; among these persons, 9.6% and 50.6% were daily and sporadic (1-2 uses over the 6-months) users, respectively. The most common sources were dealers (58.7%) and friends (31.6%). Predictors of increased risk of use of diverted buprenorphine during the 6-month follow-up included inability to access buprenorphine treatment (AOR: 7.31, 95% CI: 2.07, 25.8), meeting criteria for generalized anxiety disorder, and past 30 day use of OxyContin, methamphetamine and/or alcohol.

CONCLUSIONS

These results suggest that improving, rather than limiting, access to good quality affordable buprenorphine treatment may be an effective public health strategy to mitigate buprenorphine abuse. Future work should evaluate why more persons did not attempt to access treatment, determine how motivations change over time, and how different motivations affect diversion of the different buprenorphine formulations.

Use and misuse of opioid replacement therapies: a Queensland study

Buprenorphine/naloxone has recently been introduced in Australia and is available for unsupervised dosing within Queensland. A retrospective observational study of data collected during 2000-2007 for clients obtaining injecting equipment from the Brisbane Harm Reduction Centre in Queensland is presented. The numbers of service occasions and needles and syringes were used as surrogate drug use measures. Buprenorphine and naloxone were misused at lower rates when compared with buprenorphine and methadone. Furthermore, the misuse of opioid replacement therapies represented less than 5% of all illicit opioid injections. Implications and study limitations are discussed.

Post-marketing surveillance of buprenorphine-naloxone in Australia: diversion, injection and adherence with supervised dosing

BACKGROUND

These studies compared the diversion and injection of buprenorphine-naloxone (BNX), buprenorphine (BPN) and methadone (MET) in Australia.

METHODS

Surveys were conducted with regular injecting drug users (IDUs) (2004-2009, N=881-943), opioid substitution treatment (OST) clients (2008, N=440) and authorised OST prescribers (2007, N=291). Key outcome measures include the unsanctioned removal of supervised doses, diversion, injection, motivations, drug liking and street price. Levels of injection among IDUs were adjusted for background availability of medications. Doses not taken as directed by OST clients were adjusted by total number of daily doses dispensed.

RESULTS

Among regular IDUs, levels of injection were lower for BNX relative to BPN, but comparable to those for MET, adjusting for background availability. Among OST clients, fewer BNX clients (13%) reported recently injecting their medication, than BPN (28%) and MET clients (23%). Fewer MET clients (10%) reported removal of supervised doses, than BPN (35%) and BNX clients (22%). There were no differences in prevalence of recent diversion (28% of all OST clients). Adjusting for the total doses dispensed, more BPN was injected (10%), removed (12%) and diverted (5%), than MET (5%, <1% and 2% respectively) and BNX (5%, 9% and <1% respectively). In 2009, the median street price of BNX was equivalent to that for BPN.

CONCLUSIONS

BNX was less commonly and less frequently injected than BPN, but both sublingual medications were diverted more than liquid MET.

The pharmacodynamic and pharmacokinetic profile of intranasal crushed buprenorphine and buprenorphine/naloxone tablets in opioid abusers

AIMS

Sublingual buprenorphine and buprenorphine/naloxone are efficacious opioid dependence pharmacotherapies, but there are reports of their diversion and misuse by the intranasal route. The study objectives were to characterize and compare their intranasal pharmacodynamic and pharmacokinetic profiles.

DESIGN

A randomized, double-blind, placebo-controlled, cross-over study.

SETTING

An in-patient research unit at the University of Kentucky.

PARTICIPANTS

Healthy adults (n = 10) abusing, but not physically dependent on, intranasal opioids.

MEASUREMENTS

Six sessions (72 hours apart) tested five intranasal doses [0/0, crushed buprenorphine (2, 8 mg), crushed buprenorphine/naloxone (2/0.5, 8/2 mg)] and one intravenous dose (0.8 mg buprenorphine/0.2 mg naloxone for bioavailability assessment). Plasma samples, physiological, subject- and observer-rated measures were collected before and for up to 72 hours after drug administration.

FINDINGS

Both formulations produced time- and dose-dependent increases on subjective and physiological mu-opioid agonist effects (e.g. 'liking', miosis). Subjects reported higher subjective ratings and street values for 8 mg compared to 8/2 mg, but these differences were not statistically significant. No significant formulation differences in peak plasma buprenorphine concentration or time-course were observed. Buprenorphine bioavailability was 38-44% and T(max) was 35-40 minutes after all intranasal doses. Naloxone bioavailability was 24% and 30% following 2/0.5 and 8/2 mg, respectively.

CONCLUSIONS

It is difficult to determine if observed differences in abuse potential between intranasal buprenorphine and buprenorphine/naloxone are clinically relevant at the doses tested. Greater bioavailability and faster onset of pharmacodynamic effects compared to sublingual administration suggests a motivation for intranasal misuse in non-dependent opioid abusers. However, significant naloxone absorption from intranasal buprenorphine/naloxone administration may deter the likelihood of intranasal misuse of buprenorphine/naloxone, but not buprenorphine, in opioid-dependent individuals.

Buprenorphine and buprenorphine/naloxone diversion, misuse, and illicit use: an international review

The diversion, misuse, and non-medically supervised use of buprenorphine and buprenorphine/naloxone by opioid users are reviewed. Buprenorphine and buprenorphine/naloxone are used globally as opioid analgesics and in the treatment of opioid dependency. Diversion of buprenorphine and buprenorphine/naloxone represents a complex medical and social issue, and has been widely documented in various geographical regions throughout the world. We first discuss the clinical properties of buprenorphine and its abuse potential. Second, we discuss its diversion and illicit use on an international level, as well as motivations for those activities. Third, we examine the medical risks and benefits of buprenorphine's non-medically supervised use and misuse. These risks and benefits include the effect of buprenorphine's use on HIV risk and the risk of its concomitant use with other medications and drugs of abuse. Finally, we discuss the implications of diversion, misuse, and non-medically supervised use (including potential measures to address issues of diversion); and potential areas for further research.

Interactions between buprenorphine and antiretrovirals: nucleos(t)ide reverse transcriptase inhibitors (NRTI) didanosine, lamivudine, and tenofovir

To improve outcomes among injection drug users with HIV and/or chronic hepatitis B, it is important to identify drug interactions between antiretroviral and opiate therapies. We report the results of a study designed to examine the interaction between buprenorphine and the nucleos(t)ide reverse transcriptase inhibitors (NRTI) didanosine (ddI), lamivudine (3TC), and tenofovir (TDF). Opioid-dependent, buprenorphine/naloxone-maintained, HIV-negative volunteers (n = 27) participated in two 24-hour sessions to determine (1) pharmacokinetics of buprenorphine alone and (2) pharmacokinetics of both buprenorphine and either ddI, 3TC, or TDF. Among buprenorphine/naloxone-maintained study participants, no significant changes in buprenorphine pharmacokinetics were observed following ddI, 3TC, or TDF administration. Buprenorphine had no significant effect on NRTI concentrations. Concomitant use of buprenorphine with ddI, 3TC, or TDF results in neither a significant pharmacokinetic nor pharmacodynamic interaction.

Acute effects of intramuscular and sublingual buprenorphine and buprenorphine/naloxone in non-dependent opioid abusers

RATIONALE

Buprenorphine is a partial mu opioid receptor agonist with clinical efficacy as a pharmacotherapy for opioid dependence. A sublingual combination formulation was developed containing buprenorphine and naloxone with the intent of decreasing abuse liability in opioid-dependent individuals. However, the addition of naloxone may not limit abuse potential of this medication when taken by individuals without opioid physical dependence.

OBJECTIVES

The present study investigated the effects of buprenorphine alone and in combination with naloxone administered intramuscularly and sublingually to non-dependent opioid abusers.

METHODS

In a within-subject crossover design, non-dependent opioid-experienced volunteers (N = 8) were administered acute doses of buprenorphine (4, 8, and 16 mg) and buprenorphine/naloxone (4/1, 8/2, and 16/4 mg) via both intramuscular and sublingual routes, intramuscular hydromorphone (2 and 4 mg as an opioid agonist control), and placebo, for a total of 15 drug conditions. Laboratory sessions were conducted twice per week using a double-blind, double-dummy design.

RESULTS

Buprenorphine and buprenorphine/naloxone engendered effects similar to hydromorphone. Intramuscular administration produced a greater magnitude of effects compared to the sublingual route at the intermediate dose of buprenorphine and at both the low and high doses of the buprenorphine/naloxone combination. The addition of naloxone did not significantly alter the effects of buprenorphine.

CONCLUSIONS

These results suggest that buprenorphine and buprenorphine/naloxone have similar abuse potential in non-dependent opioid abusers, and that the addition of naloxone at these doses and in this dose ratio confers no evident advantage for decreasing the abuse potential of intramuscular or sublingual buprenorphine in this population.

Prevention of HIV infection among injection drug users in resource-limited settings

Injection drug use contributes to considerable global morbidity and mortality associated with human immunodeficiency virus (HIV) infection and AIDS and other infections due to blood-borne pathogens through the direct sharing of needles, syringes, and other injection equipment. Of approximately 16 million injection drug users (IDUs) worldwide, an estimated 3 million are HIV infected. The prevalence of HIV infection among IDUs is high in many countries in Asia and eastern Europe and could exacerbate the HIV epidemic in sub-Saharan Africa. This review summarizes important components of a comprehensive program for prevention of HIV infection in IDUs, including unrestricted legal access to sterile syringes through needle exchange programs and enhanced pharmacy services, treatment for opioid dependence (ie, methadone and buprenorphine treatment), behavioral interventions, and identification and treatment of noninjection drug and alcohol use, which accounts for increased sexual transmission of HIV. Evidence supports the effectiveness of harm-reduction programs over punitive drug-control policies.

Uses of diverted methadone and buprenorphine by opioid-addicted individuals in Baltimore, Maryland

This study examined the uses of diverted methadone and buprenorphine among opiate-addicted individuals recruited from new admissions to methadone programs and from out-of-treatment individuals recruited from the streets. Self-report data regarding diversion were obtained from surveys and semi-structured qualitative interviews. Approximately 16% (n = 84) of the total sample (N = 515) reported using diverted (street) methadone two-three times per week for six months or more, and for an average of 7.8 days (SD = 10.3) within the past month. The group reporting lifetime use of diverted methadone as compared to the group that did not report such use was less likely to use heroin and cocaine in the 30 days prior to admission (ps <.01) and had lower ASI Drug Composite scores (p <.05). Participants in our qualitative sub-sample (n = 22) indicated that street methadone was more widely used than street buprenorphine and that both drugs were largely used as self-medication for detoxification and withdrawal symptoms. Participants reported using low dosages and no injection of either medication was reported.

Methadone and buprenorphine prescribing and referral practices in US prison systems: results from a nationwide survey

BACKGROUND

More than 50% of incarcerated individuals have a history of substance use, and over 200,000 individuals with heroin addiction pass through American correctional facilities annually. Opiate replacement therapy (ORT) with methadone or buprenorphine is an effective treatment for opiate dependence and can reduce drug-related disease and recidivism for inmates. Provision of ORT is nevertheless a frequently neglected intervention in the correctional setting.

OBJECTIVE AND METHODS

We surveyed the 50 state; Washington, District of Columbia (DC); and Federal Department of Corrections' medical directors or their equivalents about their facilities' ORT prescribing policies and referral programs for inmates leaving prison.

RESULTS

We received responses from 51 of 52 prison systems nationwide. Twenty-eight prison systems (55%) offer methadone to inmates in some situations. Methadone use varies widely across states: over 50% of correctional facilities that offer methadone do so exclusively for pregnant women or for chronic pain management. Seven states' prison systems (14%) offer buprenorphine to some inmates. The most common reason cited for not offering ORT was that facilities "prefer drug-free detoxification over providing methadone or buprenorphine." Twenty-three states' prison systems (45%) provide referrals for some inmates to methadone maintenance programs after release, which increased from 8% in 2003; 15 states' prison systems (29%) provide some referrals to community buprenorphine providers.

CONCLUSION

Despite demonstrated social, medical, and economic benefits of providing ORT to inmates during incarceration and linkage to ORT upon release, many prison systems nationwide still do not offer pharmacological treatment for opiate addiction or referrals for ORT upon release.

Controversies in translational research: drug self-administration

RATIONALE

Laboratory animal and human models of drug self-administration are used to evaluate potential pharmacotherapies for drug abuse, yet the utility of these models in predicting clinically useful medications is variable.

OBJECTIVE

The objective of this study was to track how antagonist, agonist, and partial agonist medication approaches influence heroin and cocaine self-administration by rodents, non-human primates, and humans and to compare these results to clinical outcomes.

RESULTS

Across species, heroin self-administration was decreased by all three medication approaches, paralleling their demonstrated clinical utility. The heroin data emphasize the importance of assessing a medication's abuse liability preclinically to predict medication abuse and compliance and of considering subject characteristics (e.g., opioid dependence) when interpreting medication effects. For cocaine, the effects of ecopipam, modafinil, and aripiprazole were consistent in the laboratory and clinic, provided that the medications were administered repeatedly before self-administration sessions. Modafinil attenuated cocaine's reinforcing effects in the human laboratory and improved treatment outcome, while ecopipam and aripiprazole increased the reinforcing effects of cocaine and do not appear promising in the clinic.

CONCLUSIONS

The self-administration model has reliably identified medications to treat opioid dependence, and the recent data with modafinil suggest that the human laboratory model also identifies medications to treat cocaine dependence. There have been numerous false positives when subjective effects are the primary outcome measure, but not when self-administration is the outcome. Factors relevant to the predictive validity of self-administration procedures include medication maintenance and the concurrent assessment of a range of behaviors to determine abuse liability and the specificity of effect.

The role of human drug self-administration procedures in the development of medications

The purpose of this review is to illustrate the utility and value of employing human self-administration procedures in medication development, including abuse liability assessments of novel medications and evaluation of potential pharmacotherapies for substance use disorders. Traditionally, human abuse liability testing has relied primarily on subjective reports describing drug action by use of questionnaires; similarly, drug interactions between putative treatment agents and the drugs of abuse have relied on these measures. Subjective reports are highly valued because they provide qualitative and quantitative information about the characteristics of central and peripheral pharmacodynamic effects as well as safety and tolerability. However, self-administration procedures directly examine the behavior of interest-that is, drug taking. The present paper (1) reviews the most commonly used human self-administration procedures, (2) discusses the concordance of subjective reports and self-administration within the context of medications development for substance use disorders, focusing primarily on illustrative examples from development efforts with opioid and cocaine dependence, and (3) explores the utility of applying self-administration procedures to assess the abuse liability of novel compounds, including "abuse-deterrent" formulations (ADFs). The review will focus on opioid and cocaine dependence because a rich database from both clinical laboratory and clinical trial research exists for these two drug classes. The data reviewed suggest that drug-induced changes in self-administration and subjective effects are not always concordant. Therefore, assessment of self-administration in combination with subjective effects provides a more comprehensive picture that may have improved predictive validity for translating to the clinical setting.

Abuse liability of prescription opioids compared to heroin in morphine-maintained heroin abusers

Abuse of prescription opioid medications has increased dramatically in the United States during the past decade, as indicated by a variety of epidemiological sources. However, few studies have systematically examined the relative reinforcing effects of commonly abused opioid medications. The current double-blind, placebo-controlled in-patient study was designed to compare the effects of intravenously delivered fentanyl (0, 0.0625, 0.125, 0.187, and 0.250 mg/70 kg), oxycodone (0, 6.25, 12.5, 25, and 50 mg/70 kg), morphine (0, 6.25, 12.5, 25, and 50 mg/70 kg), buprenorphine (0, 0.125, 0.5, 2, and 8 mg/70 kg), and heroin (0, 3.125, 6.25, 12.5, and 25 mg/70 kg) in morphine-maintained heroin abusers (N=8 completers maintained on 120 mg per day oral morphine in divided doses (30 mg q.i.d.)). All of the participants received all of the drugs tested; drugs and doses were administered in non-systematic order. All of the drugs produced statistically significant, dose-related increases in positive subjective ratings, such as 'I feel a good drug effect' and 'I like the drug.' In general, the order of potency in producing these effects, from most to least potent, was fentanyl>buprenorphine>or=heroin >morphine=oxycodone. In contrast, buprenorphine was the only drug that produced statistically significant increases in ratings of 'I feel a bad drug effect' and it was the only drug that was not self-administered above placebo levels at any dose tested. These data suggest that the abuse liability of buprenorphine in heroin-dependent individuals may be low, despite the fact that it produces increases in positive subjective ratings. The abuse liabilities of fentanyl, morphine, oxycodone, and heroin, however, appear to be similar under these experimental conditions.

Choice of sevoflurane and its subjective and psychomotor effects in light and moderate drinkers

BACKGROUND

Sevoflurane, an inhalant of the volatile anesthetic class, has neurobiological and behavioral effects in common with abused inhalants and ethanol. We sought to determine if choice for subanesthetic doses of sevoflurane, and its subjective and psychomotor effects, would differ as a function of alcohol-drinking status in healthy volunteers.

METHODS

The effects of four concentrations of sevoflurane (0, 0.2, 0.4, 0.8% sevoflurane in oxygen) were studied in 16 light drinkers and 16 moderate drinkers. During each of four sessions, subjects sampled a concentration of sevoflurane and 100% O(2) (placebo) for 10 min each. Subjective and psychomotor testing commenced 5 min into each sampling trial. Later, within the session, subjects chose nine times, once every 5 min, among sevoflurane (e.g., "Agent A"), placebo (e.g., "Agent B," 100% O(2)), or neither (and were administered 100% O(2), identified as "drug-free air").

RESULTS

Choice for sevoflurane at the 0.4% concentration was significantly higher in the moderate drinkers than in the light drinkers. A number of subjective effects reported during inhalation of sevoflurane were markedly lower in the moderate-drinking group than in the light-drinking group. However, psychomotor impairment induced by sevoflurane was similar in magnitude in both groups.

CONCLUSIONS

Alcohol-drinking status affected sevoflurane choice. The results are consistent with several studies comparing light and heavier drinkers, using other drugs. Although both drinking groups were similarly impaired by sevoflurane, the moderate drinkers reported less of a subjective response than light drinkers, suggestive of cross-tolerance.

Buprenorphine Use: The International Experience

The confluence of the heroin injection epidemic and the human immunodeficiency virus (HIV) infection epidemic has increased the call for expanded access to effective treatments for both conditions. Buprenorphine and methadone are now listed on the World Health Organization's Model Essential Drugs List. In France, which has the most extensive experience, buprenorphine has been associated with a dramatic decrease in deaths due to overdose, and buprenorphine diversion appears to be associated with inadequate dosage, social vulnerability, and prescriptions from multiple providers. Other treatment models (in the United States, Australia, Germany, and Italy) and buprenorphine use in specific populations are also reviewed in the present article. In countries experiencing a dual epidemic of heroin use and HIV infection, such as former states of the Soviet Union and other eastern European and Asian countries, access to buprenorphine and methadone may be one potential tool for reducing the spread of HIV infection among injection drug users and for better engaging them in medical care.

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.

Depot naltrexone: antagonism of the reinforcing, subjective, and physiological effects of heroin

RATIONALE

Naltrexone is an opioid antagonist that is currently approved as a treatment for opioid and alcohol dependence. Although it is highly effective in completely antagonizing the effects of opioids, medication noncompliance is a difficult obstacle to treatment. Therefore, a sustained-release form of naltrexone may improve treatment outcome.

OBJECTIVE

The present study was designed to evaluate the time course, safety, and effectiveness of a depot formulation of naltrexone (Depotrex).

MATERIALS AND METHODS

Five heroin-dependent individuals participated in an 8-week inpatient study. After a 1-week detoxification period, the effects of a range of heroin doses (0, 6.25, 12.5, and 25 mg, i.v.) were examined. Participants then received 384 mg naltrexone base. The effects of heroin were again evaluated for the next 6 weeks. One dose of heroin was tested per day and the entire dose range was tested each week. Doses were administered in non-systematic order. During a morning sample session, participants received a dose of heroin and $20 and subjective, performance, and physiological effects were measured both before and after drug administration. During an afternoon choice session, participants were given the opportunity to choose the sampled heroin dose and/or amount of money using a modified progressive ratio procedure.

RESULTS

Depot naltrexone antagonized both the reinforcing and subjective effects of heroin for 4-5 weeks. Subjective ratings of withdrawal were reduced after week 2 and throughout the remainder of the study. The effects of heroin on mean trough pupil diameter began to emerge by week 5. There were no clinically significant effects on respiratory or cardiovascular function.

CONCLUSIONS

The present results extend our previous findings by showing that the reinforcing effects of heroin were reduced for 4-5 weeks after administration of 384 mg depot naltrexone.

Buprenorphine: clinical pharmacokinetics in the treatment of opioid dependence

Buprenorphine is a semi-synthetic opioid derived from thebaine, a naturally occurring alkaloid of the opium poppy, Papaver somniferum. The pharmacology of buprenorphine is unique in that it is a partial agonist at the opioid mu receptor. Buprenorphine undergoes extensive first-pass metabolism and therefore has very low oral bioavailability; however, its bioavailability sublingually is extensive enough to make this a feasible route of administration for the treatment of opioid dependence. The mean time to maximum plasma concentration following sublingual administration is variable, ranging from 40 minutes to 3.5 hours. Buprenorphine has a large volume of distribution and is highly protein bound (96%). It is extensively metabolised by N-dealkylation to norbuprenorphine primarily through cytochrome P450 (CYP) 3A4. The terminal elimination half-life of buprenorphine is long and there is considerable variation in reported values (mean values ranging from 3 to 44 hours). Most of a dose of buprenorphine is eliminated in the faeces, with approximately 10-30% excreted in urine. Naloxone has been added to a sublingual formulation of buprenorphine to reduce the abuse liability of the product. The presence of naloxone does not appear to influence the pharmacokinetics of buprenorphine. Buprenorphine crosses the placenta during pregnancy and also crosses into breast milk. Buprenorphine dosage does not need to be significantly adjusted in patients with renal impairment; however, since CYP3A activity may be decreased in patients with severe chronic liver disease, it is possible that the metabolism of buprenorphine will be altered in these patients. Although there is limited evidence in the literature to date, drugs that are known to inhibit or induce CYP3A4 have the potential to diminish or enhance buprenorphine N-dealkylation. It appears that the interaction between buprenorphine and benzodiazepines is more likely to be a pharmacodynamic (additive or synergistic) than a pharmacokinetic interaction. The relationship between buprenorphine plasma concentration and response in the treatment of opioid dependence has not been well studied. The pharmacokinetic and pharmacodynamic properties of buprenorphine allow it to be a feasible option for substitution therapy in the treatment of opioid dependence.