Tolerance to Opioid-Induced Respiratory Depression in Chronic High-Dose Opioid Users: A Model-Based Comparison With Opioid-Naïve Individuals

Mechanism-based organization of neural networks to emulate systems biology and pharmacology models

Deep learning neural networks are often described as black boxes, as it is difficult to trace model outputs back to model inputs due to a lack of clarity over the internal mechanisms. This is even true for those neural networks designed to emulate mechanistic models, which simply learn a mapping between the inputs and outputs of mechanistic models, ignoring the underlying processes. Using a mechanistic model studying the pharmacological interaction between opioids and naloxone as a proof-of-concept example, we demonstrated that by reorganizing the neural networks' layers to mimic the structure of the mechanistic model, it is possible to achieve better training rates and prediction accuracy relative to the previously proposed black-box neural networks, while maintaining the interpretability of the mechanistic simulations. Our framework can be used to emulate mechanistic models in a large parameter space and offers an example on the utility of increasing the interpretability of deep learning networks.

Long-term Health Outcomes of New Persistent Opioid Use After Gastrointestinal Cancer Surgery

BACKGROUND

New persistent opioid use (NPOU) after surgery has been identified as a common complication. This study sought to assess the long-term health outcomes among patients who experienced NPOU after gastrointestinal (GI) cancer surgery.

METHODS

Patients who underwent surgery for hepato-pancreato-biliary and colorectal cancer between 2007 and 2019 were identified using the Surveillance, Epidemiology, and End Results (SEER)-Medicare-linked database. Mixed-effect multivariable logistic regression and Cox proportional hazard models were used to estimate the risk of mortality and hospital visits related to falls, respiratory events, or pain symptoms.

RESULTS

Among 15,456 patients who underwent GI cancer surgery, 967(6.6%) experienced NPOU. Notably, the patients at risk for the development of NPOU were those with a history of substance abuse (odds ratio [OR], 1.45; 95% confidence interval [CI], 1.14-1.84), moderate social vulnerability (OR, 1.26; 95% CI, 1.06-1.50), an advanced disease stage (OR, 4.42; 95% CI, 3.51-5.82), or perioperative opioid use (OR, 3.07; 95% CI, 2.59-3.63. After control for competing risk factors, patients who experienced NPOU were more likely to visit a hospital for falls, respiratory events, or pain symptoms (OR, 1.45, 95% CI 1.18-1.78). Moreover, patients who experienced NPOU had a greater risk of death at 1 year (hazard ratio [HR], 2.15; 95% CI, 1.74-2.66).

CONCLUSION

Approximately 1 in 15 patients experienced NPOU after GI cancer surgery. NPOU was associated with an increased risk of subsequent hospital visits and higher mortality. Targeted interventions for individuals at higher risk for NPOU after surgery should be used to help mitigate the harmful effects of NPOU.

Physiologically based modeling reveals different risk of respiratory depression after fentanyl overdose between adults and children

Despite a rapid increase in pediatric mortality rate from prescription and illicit opioids, there is limited research on the dose-dependent impact of opioids on respiratory depression in children, the leading cause of opioid-associated death. In this article, we extend a previously developed translational model to cover pediatric populations by incorporating age-dependent pharmacokinetic, pharmacodynamic, and physiological changes compared to adults. Our model reproduced previous perioperative clinical findings that adults and children have similar risk of respiratory depression at the same plasma fentanyl concentration when specific endpoints (minute ventilation, CO2 tension in the blood) were used. However, our model points to a potential caveat that, in a perioperative setting, routine use of mechanical ventilation and supplemental oxygen maintained the blood and tissue oxygen partial pressures in patients and prevented the use of oxygen-related endpoints to evaluate the consequences of respiratory depression. In a community setting when such oxygenation procedures are not immediately available, our model suggests that the higher oxygen demand and reduced cerebrovascular reactivity could make children more susceptible to severe hypoxemia and brain hypoxia, even with the same plasma fentanyl concentration as adults. Our work indicates that when developing intervention strategies to protect children from opioid overdose in a community setting, these pediatric-specific factors may need to be considered.

Blood Oxygenation and Heart Rate Changes After Diamorphine Intravenous Injection During Opioid Agonist Treatment for Outpatients With Heroin Dependence

OBJECTIVES

More than 60 million people use opioids each year, and many countries have declared an opioid overdose crisis. Heroin, one of the most commonly used opioids, has depressant effects on autonomic functioning; however, few studies have been able to examine the effects of heroin or its pharmaceutically prepared equivalent, diamorphine, in human clinical populations. The present study examined heart rate and oxygen saturation in the minutes immediately after acute diamorphine administration in outpatients with heroin dependence.

METHODS

The sample was a subset of participants (N = 36) in the German Project of Heroin Assisted Treatment of Opiate Dependent Patients Trial in Bonn, Germany. Patients were given 3 daily doses of intravenous diamorphine. Doses were determined on an individual basis by study physicians. Pulse oximetry was recorded at baseline and at 30-second intervals from 0 to 450 seconds after diamorphine administration.

RESULTS

Heart rate was significantly higher than baseline at 30 seconds after diamorphine administration and significantly lower than baseline at 270 seconds onward. Oxygen saturation was significantly lower than baseline at 60 seconds onward.

CONCLUSIONS

Results are consistent with other studies in which depressant effects of opioids were observed. Our findings suggest that even therapeutic doses of diamorphine may have rapid and significant-predominantly depressant-effects on oxygenation and heart rate in populations that frequently use opioids. Monitoring of potential adverse opioid effects would be beneficial even in populations presumed to have developed physiological tolerance.

Investigation of monoclonal antibody CSX-1004 for fentanyl overdose

The opioid crisis in the United States is primarily driven by the highly potent synthetic opioid fentanyl leading to >70,000 overdose deaths annually; thus, new therapies for fentanyl overdose are urgently needed. Here, we present the first clinic-ready, fully human monoclonal antibody CSX-1004 with picomolar affinity for fentanyl and related analogs. In mice CSX-1004 reverses fentanyl antinociception and the intractable respiratory depression caused by the ultrapotent opioid carfentanil. Moreover, toxicokinetic evaluation in a repeat-dose rat study and human tissue cross-reactivity study reveals a favorable pharmacokinetic profile of CSX-1004 with no safety-related issues. Using a highly translational non-human primate (NHP) model of respiratory depression, we demonstrate CSX-1004-mediated protection from repeated fentanyl challenges for 3-4 weeks. Furthermore, treatment with CSX-1004 produces up to a 15-fold potency reduction of fentanyl in NHP respiration, antinociception and operant responding assays without affecting non-fentanyl opioids like oxycodone. Taken together, our data establish the feasibility of CSX-1004 as a promising candidate medication for preventing and reversing fentanyl-induced overdose.

Evolving acidic microenvironments during colitis provide selective analgesic targets for a pH-sensitive opioid

ABSTRACT

Targeting the acidified inflammatory microenvironment with pH-sensitive opioids is a novel approach for managing visceral pain while mitigating side effects. The analgesic efficacy of pH-dependent opioids has not been studied during the evolution of inflammation, where fluctuating tissue pH and repeated therapeutic dosing could influence analgesia and side effects. Whether pH-dependent opioids can inhibit human nociceptors during extracellular acidification is unexplored. We studied the analgesic efficacy and side-effect profile of a pH-sensitive fentanyl analog, (±)- N -(3-fluoro-1-phenethylpiperidine-4-yl)- N -phenyl propionamide (NFEPP), during the evolution of colitis induced in mice with dextran sulphate sodium. Colitis was characterized by granulocyte infiltration, histological damage, and acidification of the mucosa and submucosa at sites of immune cell infiltration. Changes in nociception were determined by measuring visceromotor responses to noxious colorectal distension in conscious mice. Repeated doses of NFEPP inhibited nociception throughout the course of disease, with maximal efficacy at the peak of inflammation. Fentanyl was antinociceptive regardless of the stage of inflammation. Fentanyl inhibited gastrointestinal transit, blocked defaecation, and induced hypoxemia, whereas NFEPP had no such side effects. In proof-of-principle experiments, NFEPP inhibited mechanically provoked activation of human colonic nociceptors under acidic conditions mimicking the inflamed state. Thus, NFEPP provides analgesia throughout the evolution of colitis with maximal activity at peak inflammation. The actions of NFEPP are restricted to acidified layers of the colon, without common side effects in normal tissues. N -(3-fluoro-1-phenethylpiperidine-4-yl)- N -phenyl propionamide could provide safe and effective analgesia during acute colitis, such as flares of ulcerative colitis.

Long-term Health Outcomes of New Persistent Opioid Use After Surgery Among Medicare Beneficiaries

OBJECTIVE

We examined long-term health outcomes associated with new persistent opioid use after surgery and hypothesized that patients with new persistent opioid use would have poorer overall health outcomes compared with those who did not develop new persistent opioid use after surgery.

BACKGROUND

New persistent opioid use is a common surgical complication. Long-term opioid use increases risk of mortality, fractures, and falls; however, less is known about health care utilization among older adults with new persistent opioid use after surgical care.

METHODS

We analyzed claims from a 20% national sample of Medicare beneficiaries ≥65 years undergoing surgery between January 1, 2009, and June 30, 2019. We estimated associations between new persistent use and subsequent health events between 6 and 12 months after surgery, including mortality, serious fall/fall-related injury, and respiratory or opioid/pain-related readmission/emergency department (ED) visits using a Cox proportional hazards model to estimate mortality and multivariable logistic regression for the remaining outcomes, adjusting for demographic/clinical characteristics. Our primary outcome was mortality within 6 to 12 months after surgery. Secondary outcomes included falls and readmissions or ED visits (respiratory, pain related/opioid related) within 6 to 12 months after surgery.

RESULTS

Of 229,898 patients, 6874 (3.0%) developed new persistent opioid use. Compared with patients who did not develop new persistent opioid use, patients with new persistent opioid use had a higher risk of mortality (hazard ratio 3.44, CI, 2.99-3.96), falls [adjusted odds ratio (aOR): 1.21, 95% CI, 1.05-1.39], and respiratory-related (aOR: 1.67, 95% CI, 1.49-1.86) or pain-related/opioid-related (aOR: 1.68, 95% CI, 1.55-1.82) readmissions/ED visits.

CONCLUSIONS

New persistent opioid use after surgery is associated with increased mortality and poorer health outcomes after surgery. Although the mechanisms that underlie this risk are not clear, persistent opioid use may also be a marker for greater morbidity requiring more care in the late postoperative period. Increased awareness of individuals at risk for new persistent use after surgery and close follow-up in the late postoperative period is critical to mitigate the harms associated with new persistent use.

Shared Decision Making in Acute Pain Management in Patients with Opioid Use Disorder: A Scoping Review

The treatment of acute pain over the years has changed with increasing alternative therapies and increased scrutiny of opioid prescriptions. Shared Decision Making (SDM) has become a vital tool in increasing patient engagement and satisfaction in treatment decisions. SDM has been successfully implemented in the management of pain in a variety of settings; however, information regarding the use of SDM for treating acute pain in patients with a history of opioid use disorder (OUD) remains scarce. Following the Preferred Reporting Items for Systematic Reviews and Meta-analysis Extension for Scoping Reviews (PRISMA-ScR), we conducted a review to understand how SDM is used in acute pain management in patients with OUD. We searched Medline, Embase, CINAHL, and PsychInfo databases for relevant articles. Articles were screened and SDM outcomes of eligible articles were charted. The results were grouped by sub-theme based on a 1997 SDM model. There were three original research studies and one quality improvement study. The remaining articles were split evenly between reviews and reviews of clinical guidelines. Four themes emerged from the review: prior judgment and stigma related to OUD, trust and sharing of information, clinical tools, and interprofessional teams. This scoping review consolidated and expounded the current literature on SDM in the management of acute pain in patients with OUD. More work is needed to address prior judgments by both providers and patients and to build greater dialogue. Clinical tools may aid this process as well as the involvement of a multidisciplinary team.

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.

Immunosuppression by opioids: Mechanisms of action on innate and adaptive immunity

Opioids are excellent analgesics for the clinical treatment of various types of acute and chronic pain, particularly cancer-related pain. Nevertheless, it is well known that opioids have some nasty side effects, including immunosuppression, which is commonly overlooked. As a result, the incidence of opportunistic bacterial and viral infections increases in patients with long-term opioid use. Nowadays, there are no effective medications to alleviate opioid-induced immunosuppression. Understanding the underlying molecular mechanism of opioids in immunosuppression can enable researchers to devise effective therapeutic interventions. This review comprehensively summarized the exogenous opioids-induced immunosuppressive effects and their underlying mechanisms, the regulatory roles of endogenous opioids on the immune system, the potential link between opioid immunosuppressive effect and the function of the central nervous system (CNS), and the future perspectives in this field.

Opioid epidemic: lessons learned and updated recommendations for misuse involving prescription versus non-prescription opioids

INTRODUCTION

In the past decades, the opioid crisis has heavily impacted parts of the US society and has been followed by an increase in the use of opioids worldwide. It is of paramount importance that we explore the origins of the US opioid epidemic to develop best practices to tackle the rising tide of opioid overdoses.

AREAS COVERED

In this expert review, we discuss opioid (over)prescription, change in perception of pain, and false advertisement of opioid safety as the leading causes of the US opioid epidemic. Then, we review the evidence about opioid dependence and addiction potential and provide current knowledge about predictors of aberrant opioid-related behavior. Lastly, we discuss different approaches that were considered or undertaken to combat the rising tide of opioid-related deaths by regulatory bodies, pharmaceutical companies, and health-care professionals. For this expert review, we considered published articles relevant to the topic under investigation that we retrieved from Medline or Google scholar electronic database.

EXPERT OPINION

The opioid epidemic is a dynamic process with many underlying mechanisms. Therefore, no single approach may be best suited to combat it. In our opinion, the best way forward is to employ multiple strategies to tackle different underlying mechanisms.

Development of a Translational Model to Assess the Impact of Opioid Overdose and Naloxone Dosing on Respiratory Depression and Cardiac Arrest

In response to a surge of deaths from synthetic opioid overdoses, there have been increased efforts to distribute naloxone products in community settings. Prior research has assessed the effectiveness of naloxone in the hospital setting; however, it is challenging to assess naloxone dosing regimens in the community/first-responder setting, including reversal of respiratory depression effects of fentanyl and its derivatives (fentanyls). Here, we describe the development and validation of a mechanistic model that combines opioid mu receptor binding kinetics, opioid agonist and antagonist pharmacokinetics, and human respiratory and circulatory physiology, to evaluate naloxone dosing to reverse respiratory depression. Validation supports our model, which can quantitatively predict displacement of opioids by naloxone from opioid mu receptors in vitro, hypoxia-induced cardiac arrest in vivo, and opioid-induced respiratory depression in humans from different fentanyls. After validation, overdose simulations were performed with fentanyl and carfentanil followed by administration of different intramuscular naloxone products. Carfentanil induced more cardiac arrest events and was more difficult to reverse than fentanyl. Opioid receptor binding data indicated that carfentanil has substantially slower dissociation kinetics from the opioid receptor compared to 9 other fentanyls tested, which likely contributes to the difficulty in reversing carfentanil. Administration of the same dose of naloxone intramuscularly from 2 different naloxone products with different formulations resulted in differences in the number of virtual patients experiencing cardiac arrest. This work provides a robust framework to evaluate dosing regimens of opioid receptor antagonists to reverse opioid-induced respiratory depression, including those caused by newly emerging synthetic opioids.

Association of opioid exposure before surgery with opioid consumption after surgery

Objective

To determine the effect of prescription opioid use in the year before surgery on opioid consumption after surgery.

Background

Recently developed postoperative opioid prescribing guidelines rely on data from opioid-naïve patients. However, opioid use in the USA is common, and the impact of prior opioid exposure on the consumption of opioids after surgery is unclear.

Methods

Population-based cohort study of 26,001 adults 18 years of age and older who underwent one of nine elective general or gynecologic surgical procedures between January 1, 2017 and October 31, 2019, with prospectively collected patient-reported data from the Michigan Surgical Quality Collaborative (MSQC) linked to state prescription drug monitoring program at 70 MSQC-participating hospitals on 30-day patient-reported opioid consumption in oral morphine equivalents (OME) (primary outcome).

Results

Compared with opioid-naïve participants, opioid-exposed participants (26% of sample) consumed more prescription opioids after surgery (adjusted OME difference 12, 95% CI 10 to 14). Greater opioid exposure was associated with higher postoperative consumption in a dose-dependent manner, with chronic users reporting the greatest consumption (additional OMEs 32, 95% CI 21 to 42). However, for eight of nine procedures, 90% of opioid-exposed participants consumed ≤150 OMEs. Among those receiving perioperative prescriptions, opioid-exposed participants had higher likelihood of refill (adjusted OR 4.7, 95% CI 4.4 to 5.1), number of refills (adjusted incidence rate ratio 4.0, 95% CI 3.7 to 4.3), and average refill amount (adjusted OME difference 333, 95% CI 292 to 374)).

Conclusions

Preoperative opioid use is associated with small increases in patient-reported opioid consumption after surgery for most patients, though greater differences exist for patients with chronic use. For most patients with preoperative opioid exposure, existing guidelines may meet their postoperative needs. However, guidelines may need tailoring for patients with chronic use, and providers should anticipate a higher likelihood of postoperative refills for all opioid-exposed patients.

Modelling buprenorphine reduction of fentanyl-induced respiratory depression

BACKGROUND

Potent synthetic opioids, such as fentanyl, are increasingly abused, resulting in unprecedented numbers of fatalities from respiratory depression. Treatment with the high-affinity mu-opioid receptor partial agonist buprenorphine may prevent fatalities by reducing binding of potent opioids to the opioid receptor, limiting respiratory depression.

METHODS

To characterize buprenorphine-fentanyl interaction at the level of the mu-opioid receptor in 2 populations (opioid-naive individuals and individuals who chronically use high-dose opioids), the effects of escalating i.v. fentanyl doses with range 0.075–0.35 mg/70 kg (opioid naive) and 0.25–0.70 mg/70 kg (chronic opioid use) on iso-hypercapnic ventilation at 2–3 background doses of buprenorphine (target plasma concentrations range: 0.2–5 ng/mL) were quantified using receptor association/dissociation models combined with biophase distribution models.

RESULTS

Buprenorphine produced mild respiratory depression, while high doses of fentanyl caused pronounced respiratory depression and apnea in both populations. When combined with fentanyl, buprenorphine produced a receptor binding–dependent reduction of fentanyl-induced respiratory depression in both populations. In individuals with chronic opioid use, at buprenorphine plasma concentrations of 2 ng/mL or higher, a protective effect against high-dose fentanyl was observed.

CONCLUSION

Overall, the results indicate that when buprenorphine mu-opioid receptor occupancy is sufficiently high, fentanyl is unable to activate the mu-opioid receptor and consequently will not cause further respiratory depression in addition to the mild respiratory effects of buprenorphine.

TRIAL REGISTRATION

Trialregister.nl, no. NL7028 (https://www.trialregister.nl/trial/7028)

FUNDING

Indivior Inc., North Chesterfield, Virginia, USA.

Association of pre-admission opioid abuse and/or dependence on major complications in traumatic brain injury (TBI) patients

SETTING

In the last few decades, an opioid related health crisis has been a challenging problem in many countries around the world, especially the United States. Better understanding of the association of pre-admission opioid abuse and/or dependence (POAD) on specific major complications in traumatic brain injury (TBI) patients can aid the medical team in improving patient care management and outcomes.

STUDY OBJECTIVE

Our goal is to assess and quantify the risk of POAD on in-hospital mortality and major complications in TBI patients.

DESIGN

We conducted a retrospective study and used the National Inpatient Sample (NIS) database from 2004 to 2015 to investigate the impact of POAD on in-hospital mortality and major complications in TBI patients. We utilized propensity score matching and conditional logistic regression models, adjusted with injury severity score (ISS) and comorbidities, to obtain the adjusted odds ratios (OR).

MAIN RESULTS

POAD TBI patients had lower risks of in-hospital mortality (OR 0.58; p < 0.001) and acute myocardial infarction (OR 0.53; p = 0.045), while a higher risk of respiratory (OR 1.59; p < 0.001) and neurologic complications (OR 2.54; p < 0.001), compared to non-POAD TBI patients. Additionally, POAD patients were significantly more likely to have sepsis (OR 2.16, p < 0.001), malnutrition (OR 1.56, p < 0.001), delirium (OR 2.81, p < 0.001), respiratory failure (OR 1.79, p < 0.001), and acute renal failure (OR 1.83, p < 0.001). POAD TBI patients had shorter length of hospital stay compared to non-POAD TBI patients (mean 8.0 vs 9.2 days, p < 0.001).

CONCLUSIONS

POAD TBI patients have a lower in-hospital mortality, shorter duration of hospitalization and a lower risk of acute myocardial infarction, while they are more likely to have respiratory failure, delirium, sepsis, malnutrition, and acute renal failure compared to TBI patients without POAD. Prospective study is warranted to further confirm these findings.

Changes in the development of opioid tolerance on re-exposure among people who use heroin: A qualitative study

BACKGROUND AND AIMS

This qualitative study aimed to explore how the development of tolerance to both the psychoactive and respiratory depressant effects of heroin on re-exposure are experienced by people who use heroin.

METHODS

Semi-structured one-to-one interviews were conducted with 20 adults who currently or previously used heroin (for at least 6 months), with any type of administration (injected, smoked) and experience of abstinence (at least 2 weeks) and relapse. Topic guides explored the participants understanding of tolerance, their experience of developing tolerance to heroin and of tolerance following relapse. Interviews were audio-recorded and transcribed. Thematic analysis was used to generate salient themes.

RESULTS

The analysis produced three broad themes: lay understanding of tolerance; tolerating tolerance; and rapid tolerance development following relapse. Tolerance was defined as the body adapting to regular drug use, so that the drug no longer produced the same level of effect. Tolerance was experienced as interacting and co-developing with physical dependence and the symptoms of withdrawal. Indeed, several participants did not differentiate between tolerance and dependence. Most participants did not notice tolerance to respiratory depression. Tolerance levels fluctuated-increasing over periods of regular use and reducing when abstinent. Using more drug was the most common response to increasing tolerance to the desired effects. On re-use following abstinence, tolerance was experienced as developing more quickly in the most recent relapse compared to the first. Tolerance was also perceived to return more quickly with each abstinence-relapse cycle.

CONCLUSIONS

Qualitative accounts of tolerance report that tolerance returns more quickly with each relapse episode. By elucidating the mechanism(s) involved and potentially discovering how they could be switched on prior to relapse occurring we might be able to develop a beneficial harm reduction treatment for people in abstinence that would protect against overdose occurring on subsequent relapse.

Opioid Dosage Levels, Concurrent Risk Factors and Self-Perceptions among Chronic Pain, Opioid-Managed Individuals at Elevated Risk for Opioid Overdose

While current opioid prescribing guidelines highlight a dose-response relationship between therapeutic management and overdose risk, other concurrent risk factors have also been identified. However, there is little data in assessing the relationship between risk factor prevalence, associated provider communication, and subsequent perceptions of overdose risk among chronic pain, opioid-managed (CPOM) patients. An online questionnaire was distributed in June 2020 to a sample of CPOM individuals (n = 190) treated with an opioid prescription at or above 50 daily MME, or any dosage alongside benzodiazepines. CPOM individuals reported a mean daily MME of 470, with half (52.6%) receiving a concurrent benzodiazepine prescription. All patients reported past month alcohol use, and 67.4% indicated a risk-elevating diagnosed medical condition. In assessing provider communication, 41.6% reported no discussion focusing on the risks of one’s opioid therapy. Subsequently, 62.1% perceived themselves as having “no risk”, and 60.0% were “not at all concerned” (60.0%) about experiencing an opioid overdose. Organizational policies should focus on implementing consistent methods of patient education regarding overdose risk, as well as assessments of behaviors or characteristics that my increase an individual’s risk of opioid overdose. These policies should also include other forms of evidence-based overdose risk prevention such as co-prescriptions of naloxone.

Covalently Loaded Naloxone Nanoparticles as a Long-Acting Medical Countermeasure to Opioid Poisoning

The mu opioid receptor antagonist naloxone has been a vital, long-standing countermeasure in the ongoing battle against opioid use disorders (OUD) and toxicity. However, due to its distinctive short elimination half-life, naloxone has shown diminished efficacy in cases of synthetic opioid poisoning as larger or repeated doses of the antidote have been required to achieve adequate reversal of severe respiratory depression and prevent episodes of renarcotization. This report describes the synthesis, characterization, and in vivo evaluation of a novel, nanoparticle-based naloxone formulation that provides extended protection against the toxic effects of the powerful synthetic opioid fentanyl. The strategy was predicated on a modified two-step protocol involving the synthesis and subsequent nanoprecipitation of a poly(lactic-co-glycolic acid) polymer scaffold bearing a covalently linked naloxone chain end (drug loading ∼7% w/w). Pharmacokinetic evaluation of the resulting covalently loaded naloxone nanoparticles (cNLX-NP) revealed an elimination half-life that was 34 times longer than high dose free naloxone (10 mg/kg) in male Sprague-Dawley rats. This enhancement was further demonstrated by cNLX-NP in subsequent in vivo studies affording protection against fentanyl-induced respiratory depression and antinociception for up to 48 h following a single intramuscular injection. These discoveries support further investigation of cNLX-NP as a potential therapeutic to reverse overdose and prevent renarcotization from fentanyl and its potent analogs.

Coprescription of Opioids With Other Medications and Risk of Opioid Overdose

Polypharmacy is common among patients taking prescription opioids long-term, and the codispensing of interacting medications may further increase opioid overdose risk. To identify nonopioid medications that may increase opioid overdose risk in this population, we conducted a case-crossover-based screening of electronic claims data from IBM MarketScan and Optum Clinformatics Data Mart spanning 2003 through 2019. Eligible patients were 18 years of age or older and had at least 180 days of continuous enrollment and 90 days of prescription opioid use immediately before an opioid overdose resulting in an emergency room visit or hospitalization. The main analysis quantified the odds ratio (OR) between opioid overdose and each nonopioid medication dispensed in the 90 days immediately before the opioid overdose date after adjustment for prescription opioid dosage and benzodiazepine codispensing. Additional analyses restricted to patients without cancer diagnoses and individuals who used only oxycodone for 90 days immediately before the opioid overdose date. The false discovery rate (FDR) was used to account for multiple testing. We identified 24,866 individuals who experienced opioid overdose. Baclofen (OR 1.56; FDR < 0.01; 95% confidence interval (CI), 1.29 to 1.89), lorazepam (OR 1.53; FDR < 0.01; 95% CI, 1.25 to 1.88), and gabapentin (OR 1.16; FDR = 0.09; 95% CI, 1.04 to 1.28), among other nonopioid medications, were associated with opioid overdose. Similar patterns were observed in noncancer patients and individuals who used only oxycodone. Interventions may focus on prescribing safer alternatives when a potential for interaction exists.