Prospective comparative assessment of buprenorphine overdose with heroin and methadone: clinical characteristics and response to antidotal treatment

Understanding and countering opioid-induced respiratory depression

Respiratory depression is the proximal cause of death in opioid overdose, yet the mechanisms underlying this potentially fatal outcome are not well understood. The goal of this review is to provide a comprehensive understanding of the pharmacological mechanisms of opioid-induced respiratory depression, which could lead to improved therapeutic options to counter opioid overdose, as well as other detrimental effects of opioids on breathing. The development of tolerance in the respiratory system is also discussed, as are differences in the degree of respiratory depression caused by various opioid agonists. Finally, potential future therapeutic agents aimed at reversing or avoiding opioid-induced respiratory depression through non-opioid receptor targets are in development and could provide certain advantages over naloxone. By providing an overview of mechanisms and effects of opioids in the respiratory network, this review will benefit future research on countering opioid-induced respiratory depression. LINKED ARTICLES: This article is part of a themed issue on Advances in Opioid Pharmacology at the Time of the Opioid Epidemic. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.7/issuetoc.

Mechanisms of respiratory depression induced by the combination of buprenorphine and diazepam in rats

BACKGROUND

The safety profile of buprenorphine has encouraged its widespread use. However, fatalities have been attributed to benzodiazepine/buprenorphine combinations, by poorly understood mechanisms of toxicity. Mechanistic hypotheses include (i) benzodiazepine-mediated increase in brain buprenorphine (pharmacokinetic hypothesis); (ii) benzodiazepine-mediated potentiation of buprenorphine interaction with opioid receptors (receptor hypothesis); and (iii) combined effects of buprenorphine and benzodiazepine on respiratory parameters (pharmacodynamic hypothesis).

METHODS

We studied the neuro-respiratory effects of buprenorphine (30 mg kg-1, i.p.), diazepam (20 mg kg-1, s.c.), and diazepam/buprenorphine combination in rats using arterial blood gas analysis, plethysmography, and diaphragm electromyography. Pretreatments with various opioid and gamma-aminobutyric acid receptor antagonists were tested. Diazepam impact on brain 11C-buprenorphine kinetics and binding to opioid receptors was studied using positron emission tomography imaging.

RESULTS

In contrast to diazepam and buprenorphine alone, diazepam/buprenorphine induced early-onset sedation (P<0.05) and respiratory depression (P<0.001). Diazepam did not alter 11C-buprenorphine brain kinetics or binding to opioid receptors. Diazepam/buprenorphine-induced effects on inspiratory time were additive, driven by buprenorphine (P<0.0001) and were blocked by naloxonazine (P<0.01). Diazepam/buprenorphine-induced effects on expiratory time were non-additive (P<0.001), different from buprenorphine-induced effects (P<0.05) and were blocked by flumazenil (P<0.01). Diazepam/buprenorphine-induced effects on tidal volume were non-additive (P<0.01), different from diazepam- (P<0.05) and buprenorphine-induced effects (P<0.0001) and were blocked by naloxonazine (P<0.05) and flumazenil (P<0.05). Compared with buprenorphine, diazepam/buprenorphine decreased diaphragm contraction amplitude (P<0.01).

CONCLUSIONS

Pharmacodynamic parameters and antagonist pretreatments indicate that diazepam/buprenorphine-induced respiratory depression results from a pharmacodynamic interaction between both drugs on ventilatory parameters.

A practical review of buprenorphine utilization for the emergency physician in the era of decreased prescribing restrictions

INTRODUCTION

Opioid abuse and overdose deaths have reached epidemic proportions in the last couple decades. In response to rational prescribing initiatives, utilization of prescription opioids has decreased; however, the number of deaths due to opioid overdoses continues to rise, largely driven by fentanyl analogues in adulterated heroin. Solutions to the opioid crisis must be multifaceted and address underlying opioid addiction. In recent years, buprenorphine has become a cornerstone in the treatment of opioid use disorder (OUD) and initiation of therapy in the emergency department (ED) has become increasingly common. There have also been calls by many organizations to remove the requirement for additional training and X-waiver to prescribe buprenorphine. In April 2021, the Biden Administration eased prescribing restrictions on the drug. These initiatives are expected to increase ED utilization of the buprenorphine. The purpose of this paper is to provide an updated overview of the role and use of buprenorphine in the ED setting so physicians may adapt to the changing practice environment.

OBJECTIVES

This is a narrative review describing the role of buprenorphine in the ED. A PubMed search was conducted using the keywords "opioid epidemic" "buprenorphine," and "medication assisted therapy", and "emergency department". All the articles that contained information on the opioid epidemic, medication assisted therapy, and the biological effects of buprenorphine, that were also relevant to pain management and the ED, were included in the review.

DISCUSSION

Multiple studies have pointed to the effective use of buprenorphine as a treatment for OUDs in ED patients and are superior to standard care; however, there are various barriers to its use in the ED setting.

CONCLUSION

Emergency physicians can influence opioid related morbidity and mortality, by familiarizing themselves with the use of buprenorphine to treat opioid withdrawal and addiction, particularly now that prescribing restrictions have been eased. Further ED research is necessary to assess the optimal use of buprenorphine in this care setting.

Common Opioids Involved in Drug Poisoning Presenting to the Emergency Department: A Cross-sectional Study

Objective:

Opioids poisoning is of the most important cause of mortality. The objective of the study was to compare the demographic factors, clinical manifestations, and outcomes of the most common opioids involved in drug overdose presenting to the Emergency Department.

Methods:

This cross-sectional study was conducted from October 2016 to March 2017 in the Clinical Toxicology Department of the main referral center of the university. All poisoning cases with common opioids were included in the study. Demographic factors, clinical manifestations, and outcome were recorded in a check list. ANOVA, Chi-square or Fisher's exact test, and binary logistic regression analysis were used for outcome prediction.

Findings:

Two hundred and thirty six patients with opioids poisoning were evaluated during the study period. The most common opioids involved in poisoning were methadone (47.9%), tramadol (24.2%), and opium (21.6%). Patients with opium poisoning were older than others (P < 0.0001). The rate of suicide was more in the tramadol group, while the past history of psychological problems was more observed in the methadone group (P < 0.0001). Increasing age (odds ratio [OR], 1.05; 95% confidence interval [CI]: 1.02–1.09; P = 0.05) and addiction (P = 0.01; OR, 7; 95% CI: 1.55–31.52) was associated with an increased complications or death. Also patients with somatic disease had more chance of complications/death (P = 0.04; OR, 3.71; 95% CI: 1.06–12.97). Kind of opioids was not a predictive factor in the outcome of the patients with acute poisoning.

Conclusion:

Age, addiction, and somatic disease should be considered as more important factors in outcome prediction with opioids poisoning, including opium, tramadol, and methadone.

Management of pharmaceutical and recreational drug poisoning

BACKGROUND

Poisoning is one of the leading causes of admission to the emergency department and intensive care unit. A large number of epidemiological changes have occurred over the last years such as the exponential growth of new synthetic psychoactive substances. Major progress has also been made in analytical screening and assays, enabling the clinicians to rapidly obtain a definite diagnosis.

METHODS

A committee composed of 30 experts from five scientific societies, the Société de Réanimation de Langue Française (SRLF), the Société Française de Médecine d'Urgence (SFMU), the Société de Toxicologie Clinique (STC), the Société Française de Toxicologie Analytique (SFTA) and the Groupe Francophone de Réanimation et d'Urgences Pédiatriques (GFRUP) evaluated eight fields: (1) severity assessment and initial triage; (2) diagnostic approach and role of toxicological analyses; (3) supportive care; (4) decontamination; (5) elimination enhancement; (6) place of antidotes; (7) specificities related to recreational drug poisoning; and (8) characteristics of cardiotoxicant poisoning. Population, Intervention, Comparison, and Outcome (PICO) questions were reviewed and updated as needed, and evidence profiles were generated. Analysis of the literature and formulation of recommendations were then conducted according to the GRADE® methodology.

RESULTS

The SRLF-SFMU guideline panel provided 41 statements concerning the management of pharmaceutical and recreational drug poisoning. Ethanol and chemical poisoning were excluded from the scope of these recommendations. After two rounds of discussion and various amendments, a strong consensus was reached for all recommendations. Six of these recommendations had a high level of evidence (GRADE 1±) and six had a low level of evidence (GRADE 2±). Twenty-nine recommendations were in the form of expert opinion recommendations due to the low evidences in the literature.

CONCLUSIONS

The experts reached a substantial consensus for several strong recommendations for optimal management of pharmaceutical and recreational drug poisoning, mainly regarding the conditions and effectiveness of naloxone and N-acetylcystein as antidotes to treat opioid and acetaminophen poisoning, respectively.

Buprenorphine exposures in adolescents and adults: a 10-year experience of a French Poison Control Center

Buprenorphine has been used in pain and opioid addiction management for nearly 25 years. Compared to methadone, buprenorphine is thought to exhibit less side effects and respiratory depression in case of accidental or suicidal overdose. The aim was to describe the characteristics of exposures reported to a French Poison Control Center (PCC). We conducted a retrospective study including all buprenorphine exposures for which advice of our PCC was required between 2009 and 2018. After data extraction from the electronic medical files and anonymous transfer to an Access base, a statistical descriptive analysis was performed focusing on adolescents over 10 years old and adults. One hundred and ninety-nine cases were analyzed. The major circumstances of exposure were suicide attempts and overdoses in patients with previously identified substance abuse. Buprenorphine exposures have been reduced by 50% between 2009 and 2018. Coingestions, often with benzodiazepines or antidepressants, were almost systematic and 79% of all the series exhibited at least one symptom. Among the symptomatic cases, neurological effects were the most frequent (83%) and respiratory symptoms occurred in 13%. No deaths were registered. Severity did not exceed PSS1 in 80% of all the cases. Treatment was mainly symptomatic even though naloxone was required in at least 5% of the symptomatic cases. Within 24 h after exposure, 120 patients were discharged from the emergency department. Despite loss to follow-up, our results suggest that buprenorphine is relatively safe.

Determination of buprenorphine, naloxone and phase I and phase II metabolites in rat whole blood by LC-MS/MS

Buprenorphine and buprenorphine/naloxone combination are maintenance treatments used worldwide. However, since their marketing, despite ceiling respiratory effects, poisonings and fatalities have been attributed to buprenorphine misuse and overdose. Therefore, to better understand the mechanisms of buprenorphine-related toxicity in vivo, experimental investigations have been conducted, mainly in the rat. We developed a liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method with electrospray ionization for the simultaneous quantification of buprenorphine, naloxone and their metabolites (norbuprenorphine, buprenorphine glucuronide, norbuprenorphine glucuronide and naloxone glucuronide) in rat whole blood. Compounds were extracted from whole blood by protein precipitation and chromatographically separated using gradient elution of aqueous ammonium formate and methanol in a Raptor Biphenyl core-shell column (100 mm x 3,0 mm x 2,7 μm). Following electrospray ionization, quantification was carried out in the multiple reaction monitoring (MRM) mode by the tandem mass spectrometer API 3200 system. The LC-MS/MS method was validated according to the currently accepted criteria for bioanalytical method validation. The method required small sample volumes (50 μL) and was sensitive with limits of quantification of 6.9, 6.2, 3.6, 3.3, 1.3 and 57.7 ng/mL for buprenorphine, norbuprenorphine, buprenorphine glucuronide, norbuprenorphine glucuronide, naloxone and naloxone glucuronide respectively. The upper limit of quantification was 4000 ng/ml for all the studied compounds. Trueness (88-115 %), repeatability and intermediate precision (both <15%) were in accordance with the international recommendations. The procedure was successfully used to quantify these compounds in the whole blood sample from one rat 24 h after the intravenous administration of buprenorphine/naloxone (30.0/7.5 mg/kg).

Impairment of opiate-mediated behaviors by the selective TRPV1 antagonist SB366791

Transient receptor potential vanilloid type 1 (TRPV1), the archetypal member of the vanilloid TRP family, was initially identified as the receptor for capsaicin, the pungent ingredient in hot chili peppers. We previously demonstrated that TRPV1 in the dorsal striatum significantly contributes to morphine reward by using the conditioned place preference paradigm in mice; however, it is unknown whether TRPV1 has the same effect in other reward models. In this study, we investigated the role of TRPV1 in morphine reward by using a self-administration paradigm in rats. We found that treatment with a selective TRPV1 antagonist, SB366791, significantly decreased morphine self-administration on a fixed-ratio 1 schedule or a progressive ratio schedule of reinforcement. In addition, treatment with another selective TRPV1 antagonist, AMG9810, not only significantly prevented morphine self-administration but also prevented morphine-induced c-fos expression in the nucleus accumbens. Furthermore, administration of SB366791 decreased an anxiolytic-like effect during the morphine abstinence period. Moreover, treatment with SB366791 significantly decreased morphine-priming reinstatement. Taken together, our findings suggest that blockade of TRPV1 receptors could provide an approach to limiting morphine addiction.

Clinical Presentation and the Outcome of Therapy in a Cohort of Patients with Methadone Toxicity in Iran

Background:

Agonist maintenance therapy with methadone is amongst the preferred remedies for treating opioid dependence and is increasingly supported by the regional governments in this part of the world. In this study we have investigated the clinical manifestations and factors affecting the outcome of therapy in patients with methadone poisoning in a Middle-Eastern (Iranian) referral tertiary care University hospital.

Methods:

In this prospective and descriptive-analytic study which was done in a tertiary care and referral University hospital in Iran (2012-2013) all of the admitted patients with a clear and reliable history of methadone poisoning (n=433) were included and demographic data, Clinical status on admission including Glasgow Coma Scale (GCS) score, time elapsed from ingestion to hospital admission, average dose of naloxone used, any history of psychiatric disorder, type of toxic exposure, co ingestion of other medication, hospitalization time and the outcome were recorded and statistically analyzed.

Results:

The average length of hospital stay was 33 ± 26 hours. 80.1% of patients had ingested methadone alone, and 90.3% survived. Complications were pulmonary edema (7%), aspiration pneumonia (1.4%), generalized tonic colonic seizure (0.9%), and renal failure (0.5%). GCS, systolic blood pressure and respiratory rate were lower in fatal cases and GCS had prognostic value for the outcome of therapy in methadone intoxicated patients. Patients with higher GCS on admission had better outcome [OR =0.47 (95% CI: 0.38-0.580); P value< 0.0001].

Conclusion:

Admission time GCS score maybe considered as an important predictor for the outcome of therapy in methadone poisoning.

Can differences in the type, nature or amount of polysubstance use explain the increased risk of non-fatal overdose among psychologically distressed people who inject drugs?

BACKGROUND

This study investigates whether the type, nature or amount of polysubstance use can explain the increased risk of non-fatal overdose among people who inject drugs with severe psychological distress.

METHODS

Data came from three years (2011-2013) of the Illicit Drug Reporting System (IDRS), an annual sentinel sample of injecting drug users across Australia (n=2673). Structural Equation Modelling (SEM) was used on 14 drug types to construct five latent factors, each representing a type of polysubstance use. Tests of measurement invariance were carried out to determine if polysubstance use profiles differed between those with and without severe psychological distress. Next, we regressed non-fatal overdose on the polysubstance use factors with differences in the relationships tested between groups.

FINDINGS

Among those with severe psychological distress a polysubstance use profile characterised by heroin, oxycodone, crystal methamphetamine and cocaine use was associated with greater risk of non-fatal overdose. Among those without severe psychological distress, two polysubstance use profiles, largely characterised by opioid substitution therapies and prescription drugs, were protective against non-fatal overdose.

CONCLUSION

The types of polysubstance use profiles did not differ between people who inject drugs with and without severe psychological distress. However, the nature of use of one particular polysubstance profile placed the former group at a strongly increased risk of non-fatal overdose, while the nature of polysubstance use involving opioid substitution therapies was protective only among the latter group. The findings identify polysubstance use profiles of importance to drug-related harms among individuals with psychological problems.

Need and utility of a polyethylene glycol marker to ensure against urine falsification among heroin users

BACKGROUND

Deceptive methods of falsifying urine samples are of concern for anyone who relies on accurate urine toxicology results. A novel method to combat these efforts utilizes polyethylene glycol (PEG) markers administered orally prior to providing a urine sample. By using various PEG combinations to create a tracer capsule of unique composition, each urine sample can be matched to that individual. The goal of this study was to determine the effectiveness of using the PEG marker system among active heroin users screening for research studies.

METHODS

Upon each screening visit, participants (N=55) were randomized to provide an unobserved urine sample, or the PEG tracer procedure was used. LCMS analysis was used to distinguish the PEG combinations, and allowed us to provide a unique qualitative analysis of patterns of drug use (N=168, total urine specimens).

RESULTS

The unique composition of the tracer capsules was accurately detected in 83.5% of the urine specimens. Analyses of inconsistencies implicated a number of possible attempts at fraudulence (11.4%) and investigator/lab error (5.1%). Among this sample, the concurrent use of multiple classes of psychoactive drugs was more common than not, though concomitant drug use was often underreported.

CONCLUSION

Urine drug testing should be the minimum standard for obtaining information about drug use as self-report was unreliable even in a situation where there were no perceived adverse consequences for full disclosure. In cases where there are significant pressures for individuals to falsify these data, more protective collection methods such as the PEG marker system should be considered.

A conjugate vaccine attenuates morphine- and heroin-induced behavior in rats

BACKGROUND

Currently approved medications for opioid addiction have shown clinical efficacy, but undesired side effects, dependence induced by the medications themselves, and low treatment compliance necessitate the need for novel therapies.

METHODS

A novel morphine-keyhole limpet hemocyanin conjugate vaccine was synthesized with 6-glutarylmorphine as the hapten and a lengthened linker of 6 carbon atoms. The titer and specificity of the triggered antibody were assessed by enzyme-linked immunosorbent assay. The effects of the vaccine on the morphine-induced elevation of dopamine levels in the nucleus accumbens were determined by high-performance liquid chromatography. The effects of the vaccine on morphine-induced locomotor sensitization and heroin-primed reinstatement of heroin self-administration were also assessed.

RESULTS

After subcutaneous administration in rats, the vaccine triggered a high antibody titer, with comparable specificity for morphine, 6-acetylmorphine, and heroin, but no interaction with dissimilar therapeutic opioid compounds, including buprenorphine, naloxone, and nalorphine, was observed. The vaccine significantly prevented the elevation of dopamine levels in the nucleus accumbens induced by a single morphine challenge. Moreover, the vaccine prevented the expression of morphine-induced locomotor sensitization and heroin-primed reinstatement of heroin seeking, suggesting its potential for preventing relapse.

CONCLUSION

These results demonstrate that active immunization with the present vaccine induces a robust morphine/heroin-specific antibody response in rats and attenuates the behavioral effects of morphine and heroin.

Supply of buprenorphine waivered physicians: the influence of state policies

Buprenorphine, an effective opioid use disorder treatment, can be prescribed only by buprenorphine-waivered physicians. We calculated the number of buprenorphine-waivered physicians/100,000 county residents using 2008-11 Buprenorphine Waiver Notification System data, and used multivariate regression models to predict number of buprenorphine-waivered physicians/100,000 residents in a county as a function of county characteristics, state policies and efforts to promote buprenorphine use. In 2011, 43% of US counties had no buprenorphine-waivered physicians and 7% had 20 or more waivered physicians. Medicaid funding, opioid overdose deaths, and specific state guidance for office-based buprenorphine use were associated with more buprenorphine-waivered physicians, while encouraging methadone programs to promote buprenorphine use had no impact. Our findings provide important empirical information to individuals seeking to identify effective approaches to increase the number of physicians able to prescribe buprenorphine.

Methadone toxicity in a poisoning referral center

Objective:

Methadone poisoning can occur accidentally or intentionally for suicide or homicide purposes. The aim of this study was to evaluate the epidemiological and clinical manifestations of Methadone poisoning.

Methods:

A descriptive analytical study was performed from 2010 to 2012 in the poisoning emergency and clinical toxicology departments of Noor hospital affiliated with Isfahan University of Medical Sciences (Isfahan, Iran). All patients with Methadone poisoning within this period of time were investigated. Different variables were recorded in a checklist.

Findings:

A total of 385 patients were studied. About 85.7% had ingested only Methadone and 14.3% had ingested other medications with Methadone. Mean ± standard deviation of the age was 32.1 ± 15 years (range: 1-90). Most of the patients were male (76.4%). Nearly 40% of the patients were narcotic addicts, 25.5% were addicts under surveillance of Methadone maintenance therapy centers and 34.5% were non-addicts. Intentional poisoning was observed in most of the patients (57.7%). Most of the patients had a low level of consciousness on admission (58.2%). Respiratory depression and hypotension was observed in 35.6% and 12.7% of the cases as the most common symptoms. Regarding vital signs, there was a significant difference in respiratory rate on admission among different evaluated groups (P = 0.02). Length of hospital stay was 18.79 ± 0.72 h (range: 4-240 h, median: 15 h). About 57 patients (25.8%) from the intentionally poisoned patients and 19 patients (12.3%) from the unintentionally poisoned patients had a history of psychiatric disorder (P = 0.001). Most of the patients survived without complications.

Conclusion:

Addiction, age, gender, attempt to suicide and a history of psychiatric disorder were of the most important factors effective in Methadone poisoning, which should be considered in the public training and prevention of poisoning.

Comparison of toxicity associated with nonmedical use of benzodiazepines with buprenorphine or methadone

BACKGROUND

Polysubstance use is prevalent in individuals using buprenorphine or methadone nonmedically, with benzodiazepines being a common co-ingestant. The objective of this study was to compare the severity of buprenorphine and methadone toxicity with concomitant use of benzodiazepines.

METHODS

A retrospective analysis of buprenorphine and methadone cases from November 1, 2002 to December 31, 2010 reported to the American Association of Poison Control Centers' National Poison Data System (NPDS) was conducted.

INCLUSION CRITERIA

age ≥ 18 years, nonmedical use of methadone with benzodiazepines (methadone-BZD) or buprenorphine with benzodiazepines (BUP-BZD), and case followed to a documented outcome. Cases with co-ingestants other than benzodiazepines were excluded. Clinical effects, treatments, disposition and final medical outcomes were evaluated.

RESULTS

There were 692 methadone-BZD cases and 72 BUP-BZD cases. Clinical effects in methadone-BZD and BUP-BZD groups were lethargy (71.1%, 59.7%), respiratory depression (29.0%, 15.3%), coma (22.4%, 5.6%), respiratory arrest (4.5%, 0), hypotension (11.8%, 2.8%) and cardiac arrest (1.9%, 0), respectively. Patients in the methadone-BZD group were four-times more likely to receive naloxone (60.4% vs 15.3%) or be intubated (16.3% vs 4.2%) than in the BUP-BZD group. Hospitalization rates were highest for methadone-BZD patients with 67.3% receiving medical admissions compared to 43.3% of BUP-BZD patients. Outcomes were more serious for methadone-BZD cases (p<0.0001); while there were no BUP-BZD deaths, exposure to methadone-BZD yielded 16 deaths.

CONCLUSIONS

Nonmedical use of benzodiazepines with methadone is associated with higher hospitalization rates, greater ICU utilization rates and considerably worse medical outcomes when compared to nonmedical use of benzodiazepines with buprenorphine.

Buprenorphine and norbuprenorphine determination in mice plasma and brain by gas chromatography-mass spectrometry

A gas chromatography tandem mass spectrometry method for quantification of buprenorphine (BUP) and norbuprenorphine (NBUP) in brain and plasma samples from mice was developed and validated. Analytes were extracted from the brain or plasma by solid phase extraction and quantified within 20 minutes. Calibration was achieved by linear regression with a 1/x weighting factor and d₄-buprenorphine internal standard. All products were linear from 1 to 2000 ng/mL with a correlation of determination >0.99. Assay accuracy and precision of back-calculated standards were within ±10%. The lower limit of quantification for both BUP and NBUP from the brain and plasma was 1 ng/mL. This sensitive and specific method can be used for the investigation of BUP mechanism of action and clinical profile.

Mortality among clients seeking treatment for buprenorphine abuse in Finland

BACKGROUND

It is unclear whether buprenorphine abuse is associated with a similar risk of death to other substance abuse. This study examined all-cause mortality rates and causes of deaths among clients seeking treatment for buprenorphine abuse.

METHODS

Structured clinical interviews were conducted with 4685 clients between January 1998 and August 2008. Records of deaths that occurred among these clients were extracted from the Official Causes of Death Register in Finland. Standardized mortality ratios (SMRs) with 95% confidence intervals (CI) were computed using national mortality rates over a 13-year follow-up to examine excess mortality. Kaplan-Meier survival analysis was used to compare survival between buprenorphine and other clients.

RESULTS

Sixty-one of 780 (7.8%) clients who sought treatment for buprenorphine abuse and 408 of 3905 (10.4%) other clients died during the 13-year follow-up period. The most common cause of death was drug-related in buprenorphine (n=25, 41.0%) and other clients (n=142, 34.8%). Survival rates were similar among buprenorphine and other clients (log-rank χ[df=1](2)=0.215, p=0.643). The SMR was 3.0 (95% CI 2.3-3.8) and 3.1 (95% CI 2.8-3.4) for buprenorphine and other clients, respectively. Excess mortality was highest among women aged 20-29 years, and more pronounced in buprenorphine clients (SMR 27.9 [95% CI 12.6-49.0]) compared to other clients (SMR 14.0 [95% CI 9.3-19.6]).

CONCLUSIONS

Clients seeking treatment for buprenorphine abuse had a three times higher mortality rate than the national average, with the excess risk highest among female clients. Overall mortality rates were similar among clients seeking treatment for buprenorphine and other substance abuse.

Chronic opioid use during pregnancy: maternal and fetal implications

Current trends in the United States suggest that chronic narcotic use has increased in reproductive aged women over the past 10 years. Regular exposure to such substances during pregnancy has maternal and fetal implications. Appropriate prenatal care is critical to optimizing outcomes. Management options for narcotic dependence should be patient-specific and may include discontinuation of narcotics with careful observation, limitation of prescription dispensing, or substitution therapy with methadone or buprenorphine. A multidisciplinary, collaborative approach is highly recommended. This review discusses usage of narcotic medications, associated maternal and fetal risks, and management strategies for the antepartum, intrapartum, and postpartum periods.

Respiratory effects of diazepam/methadone combination in rats: a study based on concentration/effect relationships

BACKGROUND

Methadone may cause respiratory depression and fatalities. Concomitant use of benzodiazepines in methadone-treated patients for chronic pain or as maintenance therapy for opiate abuse is common. However, the exact contribution of benzodiazepines to methadone-induced respiratory toxicity remains debatable.

METHODS

We investigated the respiratory effects of the combination diazepam (20mg/kg)/methadone (5mg/kg) in the rat, focusing on methadone concentration/effect relationships. Respiratory effects were studied using arterial blood gases and whole-body plethysmography. Plasma concentrations of both R- and S-methadone enantiomers were measured using high-performance liquid chiral chromatography coupled to mass spectrometry. To clarify mechanisms of diazepam/methadone interaction, methadone metabolism was investigated in vitro using rat liver microsomes.

RESULTS

Diazepam/methadone co-administration significantly increased methadone-related effects on inspiratory time (p<0.001) but did not significantly alter the other respiratory parameters when compared with methadone alone, despite significant increase in the area under the curve of plasma R-methadone concentrations measured during 240 min (p<0.05). Diazepam/methadone co-incubation with microsomes in vitro resulted in a significant inhibition of methadone metabolism (p<0.01), with 50%-inhibitory diazepam concentrations of 25.02 ± 0.18 μmol/L and 25.18 ± 0.23 μmol/L for R- and S-methadone, respectively.

CONCLUSION

We concluded that co-administration of high-doses of diazepam and methadone in rats is not responsible for additional respiratory depression in comparison to methadone alone, despite significant metabolic interaction between the drugs. In humans, although our experimental data may suggest the relative safety of benzodiazepine/methadone co-prescription, physicians should remain cautious as other underlying conditions may enhance this drug-drug interaction.

Dynamic vaccine blocks relapse to compulsive intake of heroin

Heroin addiction, a chronic relapsing disorder characterized by excessive drug taking and seeking, requires constant psychotherapeutic and pharmacotherapeutic interventions to minimize the potential for further abuse. Vaccine strategies against many drugs of abuse are being developed that generate antibodies that bind drug in the bloodstream, preventing entry into the brain and nullifying psychoactivity. However, this strategy is complicated by heroin's rapid metabolism to 6-acetylmorphine and morphine. We recently developed a "dynamic" vaccine that creates antibodies against heroin and its psychoactive metabolites by presenting multihaptenic structures to the immune system that match heroin's metabolism. The current study presents evidence of effective and continuous sequestration of brain-permeable constituents of heroin in the bloodstream following vaccination. The result is efficient blockade of heroin activity in treated rats, preventing various features of drugs of abuse: heroin reward, drug-induced reinstatement of drug seeking, and reescalation of compulsive heroin self-administration following abstinence in dependent rats. The dynamic vaccine shows the capability to significantly devalue the reinforcing and motivating properties of heroin, even in subjects with a history of dependence. In addition, targeting a less brain-permeable downstream metabolite, morphine, is insufficient to prevent heroin-induced activity in these models, suggesting that heroin and 6-acetylmorphine are critical players in heroin's psychoactivity. Because the heroin vaccine does not target opioid receptors or common opioid pharmacotherapeutics, it can be used in conjunction with available treatment options. Thus, our vaccine represents a promising adjunct therapy for heroin addiction, providing continuous heroin antagonism, requiring minimal medical monitoring and patient compliance.

Respiratory toxicity of buprenorphine results from the blockage of P-glycoprotein-mediated efflux of norbuprenorphine at the blood-brain barrier in mice

OBJECTIVES

Deaths due to asphyxia as well as following acute poisoning with severe respiratory depression have been attributed to buprenorphine in opioid abusers. However, in human and animal studies, buprenorphine exhibited ceiling respiratory effects, whereas its metabolite, norbuprenorphine, was assessed as being a potent respiratory depressor in rodents. Recently, norbuprenorphine, in contrast to buprenorphine, was shown in vitro to be a substrate of human P-glycoprotein, a drug-transporter involved in all steps of pharmacokinetics including transport at the blood-brain barrier. Our objectives were to assess P-glycoprotein involvement in norbuprenorphine transport in vivo and study its role in the modulation of buprenorphine-related respiratory effects in mice.

SETTING

University-affiliated research laboratory, INSERM U705, Paris, France.

SUBJECTS

Wild-type and P-glycoprotein knockout female Friend virus B-type mice.

INTERVENTIONS

Respiratory effects were studied using plethysmography and the P-glycoprotein role at the blood-brain barrier using in situ brain perfusion.

MEASUREMENTS AND MAIN RESULTS

Norbuprenorphine(≥ 1 mg/kg) and to a lesser extent buprenorphine (≥ 10 mg/kg) were responsible for dose-dependent respiratory depression combining increased inspiratory (TI) and expiratory times (TE). PSC833, a powerful P-glycoprotein inhibitor, significantly enhanced buprenorphine-related effects on TI (p < .01) and TE (p < .05) and norbuprenorphine-related effects on minute volume (VE, p < .05), TI, and TE (p < .001). In P-glycoprotein-knockout mice, buprenorphine-related effects on VE (p < .01), TE (p < .001), and TI (p < .05) and norbuprenorphine-related effects on VE (p < .05) and TI (p < .001) were significantly enhanced. Plasma norbuprenorphine concentrations were significantly increased in PSC833-treated mice (p < .001), supporting a P-glycoprotein role in norbuprenorphine pharmacokinetics. Brain norbuprenorphine efflux was significantly reduced in PSC833-treated and P-glycoprotein-knockout mice (p < .001), supporting P-glycoprotein-mediated norbuprenorphine transport at the blood-brain barrier.

CONCLUSIONS

P-glycoprotein plays a key-protective role in buprenorphine-related respiratory effects, by allowing norbuprenorphine efflux at the blood-brain barrier. Our findings suggest a major role for drug-drug interactions that lead to P-glycoprotein inhibition in buprenorphine-associated fatalities and respiratory depression.

Polydrug abuse: a review of opioid and benzodiazepine combination use

This paper reviews studies examining the pharmacological interactions and epidemiology of the combined use of opioids and benzodiazepines (BZDs). A search of English language publications from 1970 to 2012 was conducted using PubMed and PsycINFO(®). Our search found approximately 200 articles appropriate for inclusion in this paper. While numerous reports indicate that the co-abuse of opioids and BZDs is ubiquitous around the world, the reasons for the co-abuse of these medications are not entirely clear. Though the possibility remains that opioid abusers are using BZDs therapeutically to self-medicate anxiety, mania or insomnia, the data reviewed in this paper suggest that BZD use is primarily recreational. For example, co-users report seeking BZD prescriptions for the purpose of enhancing opioid intoxication or "high," and use doses that exceed the therapeutic range. Since there are few clinical studies investigating the pharmacological interaction and abuse liability of their combined use, this hypothesis has not been extensively evaluated in clinical settings. As such, our analysis encourages further systematic investigation of BZD abuse among opioid abusers. The co-abuse of BZDs and opioids is substantial and has negative consequences for general health, overdose lethality, and treatment outcome. Physicians should address this important and underappreciated problem with more cautious prescribing practices, and increased vigilance for abusive patterns of use.

Illicit use of buprenorphine/naloxone among injecting and noninjecting opioid users

OBJECTIVES

We examined the use, procurement, and motivations for the use of diverted buprenorphine/naloxone among injecting and noninjecting opioid users in an urban area.

METHODS

A survey was self-administered among 51 injecting opioid users and 49 noninjecting opioid users in Providence, RI. Participants were recruited from a fixed-site syringe exchange program and a community outreach site between August and November 2009.

RESULTS

A majority (76%) of participants reported having obtained buprenorphine/naloxone illicitly, with 41% having done so in the previous month. More injection drug users (IDUs) than non-IDUs reported the use of diverted buprenorphine/naloxone (86% vs 65%, P = 0.01). The majority of participants who had used buprenorphine/naloxone reported doing so to treat opioid withdrawal symptoms (74%) or to stop using other opioids (66%) or because they could not afford drug treatment (64%). More IDUs than non-IDUs reported using diverted buprenorphine/naloxone for these reasons. Significantly more non-IDUs than IDUs reported ever using buprenorphine/naloxone to "get high" (69% vs 32%, P < 0.01). The majority of respondents, both IDUs and non-IDUs, were interested in receiving treatment for opioid dependence, with greater reported interest in buprenorphine/naloxone than in methadone. Common reasons given for not being currently enrolled in a buprenorphine/naloxone program included cost and unavailability of prescribing physicians.

CONCLUSIONS

The use of diverted buprenorphine/naloxone was common in our sample. However, many opioid users, particularly IDUs, were using diverted buprenorphine/naloxone for reasons consistent with its therapeutic purpose, such as alleviating opioid withdrawal symptoms and reducing the use of other opioids. These findings highlight the need to explore the full impact of buprenorphine/naloxone diversion and improve the accessibility of buprenorphine/naloxone through licensed treatment providers.

The World Federation of Societies of Biological Psychiatry (WFSBP) guidelines for the biological treatment of substance use and related disorders. Part 2: Opioid dependence

OBJECTIVES

To develop evidence-based practice guidelines for the pharmacological treatment of opioid abuse and dependence.

METHODS

An international task force of the World Federation of Societies of Biological Psychiatry (WFSBP) developed these practice guidelines after a systematic review of the available evidence pertaining to the treatment of opioid dependence. On the basis of the evidence, the Task Force reached a consensus on practice recommendations, which are intended to be clinically and scientifically meaningful for physicians who treat adults with opioid dependence. The data used to develop these guidelines were extracted primarily from national treatment guidelines for opioid use disorders, as well as from meta-analyses, reviews, and publications of randomized clinical trials on the efficacy of pharmacological and other biological treatments for these disorders. Publications were identified by searching the MEDLINE database and the Cochrane Library. The literature was evaluated with respect to the strength of evidence for efficacy, which was categorized into one of six levels (A-F).

RESULTS

There is an excellent evidence base supporting the efficacy of methadone and buprenorphine or the combination of buprenorphine and naloxone for the treatment of opioid withdrawal, with clonidine and lofexidine as secondary or adjunctive medications. Opioid maintenance with methadone and buprenorphine is the best-studied and most effective treatment for opioid dependence, with heroin and naltrexone as second-line medications.

CONCLUSIONS

There is enough high quality data to formulate evidence-based guidelines for the treatment of opioid abuse and dependence. This task force report provides evidence for the efficacy of a number of medications to treat opioid abuse and dependence, particularly the opioid agonists methadone or buprenorphine. These medications have great relevance for clinical practice.