Predictors of induction onto extended-release naltrexone among unemployed heroin-dependent adults

Patient characteristics associated with initiation of XR-naltrexone for opioid use disorder in clinical trials

BACKGROUND

Extended-release injectable naltrexone (XR-naltrexone) is effective for treatment of patients with opioid use disorder (OUD), but initiation remains a barrier due to the challenge of tolerating opioid withdrawal prior to administration. Understanding factors associated with successful initiation of XR-naltrexone could facilitate its implementation through patient-treatment matching.

METHODS

We combined data from five consecutive studies that sought to initiate patients with active opioid use onto XR-naltrexone using a rapid procedure consisting of minimal buprenorphine, non-opioid medications for treating opioid withdrawal, and ascending low doses of oral naltrexone. Associations between patient characteristics and initiating naltrexone were estimated with logistic regression models. To evaluate whether associations differed between inpatient and outpatient settings, patient characteristic-by-setting interactions were also estimated.

RESULTS

409 patients were included in the analyses and 228 (56%) received the first injection. A significantly greater percent of inpatients (62%) vs outpatients (48%) initiated XR-naltrexone. Initiation success was significantly more likely on an inpatient basis for heroin (60.9% inpatient vs 36.2% outpatient), intravenous (56.3% inpatient vs 22.5% outpatient), and speedball users (68.1% inpatient vs 32.3% outpatient). Prescription opioid users showed similar, higher initiation rates across settings (68.9% inpatient; 73.7% outpatient).

CONCLUSIONS

An inpatient setting may be the preferred strategy for rapid initiation of XR-naltrexone for opioid users with greater severity, including heroin or speedball injection users or those who use opioids intravenously. Initiation on an outpatient basis may be more likely to succeed for prescription opioid users.

Monitoring and Improving Naltrexone Adherence in Patients with Substance Use Disorder

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

The relationship between cannabis use and patient outcomes in medication-based treatment of opioid use disorder: A systematic review

Despite high rates of cannabis use during medication-based treatment of opioid use disorder (MOUD), uncertainty remains around how cannabis influences treatment outcomes. We sought to investigate the relationship between cannabis use during MOUD and a number of patient outcomes. We searched seven databases for original peer-reviewed studies documenting the relationship between cannabis use and at least one primary outcome (opioid use, treatment adherence, or treatment retention) among patients enrolled in methadone-, buprenorphine-, or naltrexone-based therapy for OUD. In total, 41 articles (including 23 methadone, 7 buprenorphine, 6 naltrexone, and 5 mixed modalities) were included in this review. For each primary outcome area, there was a small number of studies that produced findings suggestive of a supportive or detrimental role of concurrent cannabis use, but the majority of studies reported that cannabis use was not statistically significantly associated with the outcome. No studies of naltrexone treatment demonstrated significantly worse outcomes for cannabis users. We identified methodological shortcomings and future research priorities, including exploring the potential role of adjunct cannabis use for improving opioid craving and withdrawal during MOUD. While monitoring for cannabis use may help guide clinicians towards an improved treatment plan, cannabis use is unlikely to independently threaten treatment outcomes.

Endogenous Opiates and Behavior: 2018

This paper is the forty-first consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2018 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (2), the roles of these opioid peptides and receptors in pain and analgesia in animals (3) and humans (4), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (5), opioid peptide and receptor involvement in tolerance and dependence (6), stress and social status (7), learning and memory (8), eating and drinking (9), drug abuse and alcohol (10), sexual activity and hormones, pregnancy, development and endocrinology (11), mental illness and mood (12), seizures and neurologic disorders (13), electrical-related activity and neurophysiology (14), general activity and locomotion (15), gastrointestinal, renal and hepatic functions (16), cardiovascular responses (17), respiration and thermoregulation (18), and immunological responses (19).

Changes in cardiac vagal tone as measured by heart rate variability during naloxone-induced opioid withdrawal

BACKGROUND

Heart rate variability (HRV) is of interest to researchers due to its potential utility as a marker for both physiological and psychological stress. Sympatholytics are used to treat opioid withdrawal, but little information about the parasympathetic system's role in mediating withdrawal symptoms exists. The goal of the current study was to evaluate changes in HRV during opioid withdrawal to provide a better understanding of the autonomic effects of opioid withdrawal.

METHODS

Ten male participants (mean age = 46.4 years) received intramuscular naloxone (mean dose =0.26 mg) to confirm opioid dependence. The presence and severity of withdrawal symptoms were assessed using subjective and objective measures (Wang et al., 1974). Electrocardiography (ECG) was measured continuously, and HRV was analyzed in 2-minute segments before naloxone injection (at baseline) and after participants were in moderate withdrawal (Wang Test score ≥10). Heart rate, blood pressure, pupil diameter, and respiratory rate were also examined.

RESULTS

Pupil diameter significantly increased after naloxone administration relative to baseline (t(9) = 5.562, p = 0.000). Both high frequency (HF) HRV (Z = -2.803, p = 0.005) and root mean square of successive differences (RMSSD) HRV (Z = -2.090, p = 0.037) were significantly lower during withdrawal relative to baseline. Increases in heart rate (Z = -2.090, p = 0.032) and systolic pressure (t(9) = 8.099, p = 0.0000) from baseline to withdrawal also were significant.

CONCLUSIONS

These preliminary data indicate that a large reduction in cardiac vagal tone occurs during naloxone-induced withdrawal. This finding underscores the need for further research into the role of the parasympathetic nervous system in opioid withdrawal.

Medication Treatment For Opioid Use Disorders In Substance Use Treatment Facilities

Medication treatment (MT) is one of the few evidence-based strategies proposed to combat the current opioid epidemic. We examined national trends and correlates of offering MT in substance use treatment facilities in the United States. According to data from national surveys, the proportion of these facilities that offered any MT increased from 20.0 percent in 2007 to 36.1 percent in 2016-mainly the result of increases in offering buprenorphine and extended-release naltrexone. Only 6.1 percent of facilities offered all three MT medications in 2016. Facilities in states with higher opioid overdose death rates, facilities that accepted health insurance overall (and, more specifically, those that accepted Medicaid in states that opted to expand eligibility for Medicaid), and facilities in states with more comprehensive coverage of MT under their Medicaid plans had higher odds of offering MT. The findings highlight the persistent unmet need for MT nationally and the role of expansion of health insurance in the dissemination of these treatments.

The effects of extended-release injectable naltrexone and incentives for opiate abstinence in heroin-dependent adults in a model therapeutic workplace: A randomized trial

AIM

To determine whether extended-release injectable naltrexone (XR-NTX), incentives for opiate abstinence, and their combination reduce opiate use compared to a usual care control and whether the combination reduces opiate use compared to either treatment alone.

DESIGN

Randomized 2 × 2 single-site controlled trial conducted from November 2012 through May 2016. After a detoxification and oral naltrexone induction, participants were assigned to a Usual Care, Abstinence Incentives, XR-NTX, or XR-NTX plus Abstinence Incentives group for a six-month intervention period.

SETTING

A model therapeutic workplace where participants could work on automated computer programs that targeted job-skills training for 4 h every weekday for 24 weeks and earn about $10 per hour.

PARTICIPANTS

84 heroin-dependent adults who were unemployed and medically approved for naltrexone. Most participants were male (71.4%), African American (80.1%), and cocaine dependent (71.4%).

MEASUREMENTS

The primary outcome measure was the percentage of urine samples negative for opiates that were collected at once weekly assessments (24 per participant) that were not part of the intervention and for which participants were paid $10 for completing.

INTERVENTION

Participants who attended the workplace provided thrice-weekly urine samples. Abstinence Incentives participants had to provide opiate-free urine samples to maintain maximum pay. XR-NTX participants received one injection every 4 weeks and were required to take injections in order to work and to maintain maximum pay. Usual Care participants were not offered XR-NTX and opiate urinalysis results did not affect pay.

FINDINGS

A large percentage (65 of 149; 43.6%) of individuals failed the induction protocol required for randomization and to be eligible to receive XR-NTX. When missing urine samples were considered positive, there was no significant interaction between XR-NTX and Abstinence Incentives. XR-NTX plus Abstinence Incentives participants provided significantly more opiate-negative samples (81.3%, SD 39.0%) than XR-NTX participants (64.5%, SD 47.9%; aOR 10.4, 95% CI 1.3-85.5; P = .030). When urine samples were not replaced, there was a significant interaction between XR-NTX and Abstinence Incentives (aOR 77.0, 95% CI 1.3-4432;P = 0.036); XR-NTX plus Abstinence Incentives participants provided significantly more opiate-negative samples (99.6%, SD 0.1%) than XR-NTX participants (85.0%, SD 35.7%; aOR 147.6, 95% CI 6.3-3472; P = 0.002), Abstinence Incentives participants (91.9%, SD 27.3%; aOR 121.7, 95% CI 4.8-3067; P =0.004), and Usual Care participants (78.7%, SD 41.0%; aOR 233.4, 95% CI 9.4-5814; P <.001). No other group differences were significant.

CONCLUSION

XR-NTX plus incentives for opiate abstinence increased opiate abstinence, but XR-NTX alone did not. XR-NTX can promote opiate abstinence when it is combined with incentives for opiate abstinence in a model therapeutic workplace.

Extended-release injectable naltrexone for opioid use disorder: a systematic review

AIMS

To review systematically the published literature on extended-release naltrexone (XR-NTX, Vivitrol^® ), marketed as a once-per-month injection product to treat opioid use disorder. We addressed the following questions: (1) how successful is induction on XR-NTX; (2) what are adherence rates to XR-NTX; and (3) does XR-NTX decrease opioid use? Factors associated with these outcomes as well as overdose rates were examined.

METHODS

We searched PubMed and used Google Scholar for forward citation searches of peer-reviewed papers from January 2006 to June 2017. Studies that included individuals seeking treatment for opioid use disorder who were offered XR-NTX were included.

RESULTS

We identified and included 34 studies. Pooled estimates showed that XR-NTX induction success was lower in studies that included individuals that required opioid detoxification [62.6%, 95% confidence interval (CI) = 54.5-70.0%] compared with studies that included individuals already detoxified from opioids (85.0%, 95% CI = 78.0-90.1%); 44.2% (95% CI = 33.1-55.9%) of individuals took all scheduled injections of XR-NTX, which were usually six or fewer. Adherence was higher in prospective investigational studies (i.e. studies conducted in a research context according to a study protocol) compared to retrospective studies of medical records taken from routine care (6-month rates: 46.7%, 95% CI = 34.5-59.2% versus 10.5%, 95% CI = 4.6-22.4%, respectively). Compared with referral to treatment, XR-NTX reduced opioid use in adults under criminal justice supervision and when administered to inmates before release. XR-NTX reduced opioid use compared with placebo in Russian adults, but this effect was confounded by differential retention between study groups. XR-NTX showed similar efficacy to buprenorphine when randomization occurred after detoxification, but was inferior to buprenorphine when randomization occurred prior to detoxification.

CONCLUSIONS

Many individuals intending to start extended-release naltrexone (XR-NTX) do not and most who do start XR-NTX discontinue treatment prematurely, two factors that limit its clinical utility significantly. XR-NTX appears to decrease opioid use but there are few experimental demonstrations of this effect.

Development of a Clinically Viable Heroin Vaccine

Heroin is a highly abused opioid and incurs a significant detriment to society worldwide. In an effort to expand the limited pharmacotherapy options for opioid use disorders, a heroin conjugate vaccine was developed through comprehensive evaluation of hapten structure, carrier protein, adjuvant and dosing. Immunization of mice with an optimized heroin-tetanus toxoid (TT) conjugate formulated with adjuvants alum and CpG oligodeoxynucleotide (ODN) generated heroin "immunoantagonism", reducing heroin potency by >15-fold. Moreover, the vaccine effects proved to be durable, persisting for over eight months. The lead vaccine was effective in rhesus monkeys, generating significant and sustained antidrug IgG titers in each subject. Characterization of both mouse and monkey antiheroin antibodies by surface plasmon resonance (SPR) revealed low nanomolar antiserum affinity for the key heroin metabolite, 6-acetylmorphine (6AM), with minimal cross reactivity to clinically used opioids. Following a series of heroin challenges over six months in vaccinated monkeys, drug-sequestering antibodies caused marked attenuation of heroin potency (>4-fold) in a schedule-controlled responding (SCR) behavioral assay. Overall, these preclinical results provide an empirical foundation supporting the further evaluation and potential clinical utility of an effective heroin vaccine in treating opioid use disorders.