Overdose mortality rates for opioids and stimulant drugs are substantially higher in men than in women: state-level analysis

Sex Differences in the Development of an Opioid Addiction-Like Phenotype: A Focus on the Telescoping Effect

Background

Women develop addiction and drug-related health consequences after fewer years of drug use than men; this accelerated time course, or telescoping effect, has been observed clinically for multiple drugs, including opioids. Preclinical studies indicate that this is a biologically based phenomenon; however, these studies have focused exclusively on cocaine, and none have considered health effects.

Methods

In this study, we used a rat (Sprague Dawley) model to determine sex differences in the time course for the development of an opioid addiction-like phenotype, as defined by the development of physical dependence (withdrawal-induced weight loss) and an increase in motivation for fentanyl (under a progressive-ratio schedule). Effects were determined following either 10 days (optimized, experiment 1) or 3 days (threshold, experiment 2) of extended-access fentanyl self-administration (24 hours/day, fixed ratio 1, 2- to 5-minute trials/hour) or following short-access fentanyl self-administration (subthreshold, experiment 3; fixed ratio 1, up to 40 infusions/day). Opioid-related adverse health effects were also determined (experiment 4).

Results

Motivation for fentanyl was similarly increased in males and females following 10 days of extended-access self-administration (experiment 1), was transiently increased in females, but not males, following 3 days of extended-access self-administration (experiment 2) and was not increased in either sex following short-access self-administration (experiment 3). Females developed fentanyl-associated adverse health effects more readily than males (experiment 4), with particularly robust differences during extended-access self-administration and withdrawal.

Conclusions

As with findings in humans, female rats developed opioid addiction-like features and adverse health consequences more readily than male rats. These data provide support for a biologically based telescoping effect in females for opioids, particularly for opioid-related adverse health consequences.

Gut Hormones: Possible Mediators of Addictive Disorders?

BACKGROUND

Alcohol and drug dependence are major health and economic burdens to society. One of the major challenges to reducing this burden will be to develop more effective and better tolerated medications that target alternative mechanisms in the brain. While the dopamine system has been well characterized for mediating the reward value of drugs, there is evidence that the endocrine system also conveys signals to the same neural systems using gut hormones.

SUMMARY

These gut hormones, produced in the stomach and intestine and that regulate food intake, have also been shown to control the use of other substances, such as alcohol and drugs of abuse. Examples of such hormones are ghrelin and glucagon-like peptide-1, which exert their effects on dopamine transmission in parts of the brain known to be involved in some of the core features of addiction, such as reward sensitivity.

KEY MESSAGES

This raises the possibility that gut hormone systems may play a pivotal role in addictive disorders. This review will briefly outline emerging evidence that the ghrelin and glucagon-like peptide-1 hormones are contrasting mediators of alcohol and drug use and may present a promising alternative target for treatment intervention in addictive disorders.

The Mitragyna speciosa (kratom) alkaloid mitragynine: Analysis of adrenergic α2 receptor activity in vitro and in vivo

Mitragynine, an alkaloid present in the leaves of Mitragyna speciosa (kratom), has a complex pharmacology that includes low efficacy agonism at μ-opioid receptors (MORs). This study examined the activity of mitragynine at adrenergic α2 receptors (Aα2Rs) in vitro and in vivo. Mitragynine displaced a radiolabeled Aα2R antagonist ([3H]RX821002) from human Aα2ARs in vitro with lower affinity (Ki = 1260 nM) than the agonists (-)-epinephrine (Ki = 263 nM) or lofexidine (Ki = 7.42 nM). Mitragynine did not significantly stimulate [35S]GTPγS binding at Aα2ARs in vitro, but in rats trained to discriminate 32 mg/kg mitragynine from vehicle (intraperitoneally administered; i.p.), mitragynine exerted an Aα2R agonist-like effect. Both α2R antagonists (atipamezole and yohimbine) and MOR antagonists (naloxone and naltrexone) produced rightward shifts in mitragynine discrimination dose-effect function and Aα2R agonists lofexidine and clonidine produced leftward shifts. In the mitragynine trained rats, Aα2R agonists also produced leftward shifts in discrimination dose-effect functions for morphine and fentanyl. In a separate rat cohort trained to discriminate 3.2 mg/kg i.p. morphine from vehicle, naltrexone produced a rightward shift, but neither an Aα2R agonist or antagonist affected morphine discrimination. In a hypothermia assay, both lofexidine and clonidine produced marked effects antagonized by yohimbine. Mitragynine did not produce hypothermia. Together, these data demonstrate that mitragynine acts in vivo like an Aα2R agonist, although its failure to induce hypothermia or stimulate [35S]GTPγS binding in vitro, suggests that mitragynine maybe a low efficacy Aα2R agonist.

In vitro and in vivo study of butyrylfentanyl and 4-fluorobutyrylfentanyl in female and male mice: Role of the CRF1 receptor in cardiorespiratory impairment

BACKGROUND AND PURPOSE

Fentanyl analogues have been implicated in many cases of intoxication and death with overdose worldwide. The aim of this study is to investigate the pharmaco-toxicology of two fentanyl analogues: butyrylfentanyl (BUF) and 4-fluorobutyrylfentanyl (4F-BUF).

EXPERIMENTAL APPROACH

In vitro, we measured agonist opioid receptor efficacy, potency, and selectivity and ability to promote interaction of the μ receptor with G protein and β-arrestin 2. In vivo, we evaluated thermal antinociception, stimulated motor activity and cardiorespiratory changes in female and male CD-1 mice injected with BUF or 4F-BUF (0.1-6 mg·kg-1). Opioid receptor specificity was investigated using naloxone (6 mg·kg-1). We investigated the possible role of stress in increasing cardiorespiratory toxicity using the corticotropin-releasing factor 1 (CRF1) antagonist antalarmin (10 mg·kg-1).

KEY RESULTS

Agonists displayed the following rank of potency at μ receptors: fentanyl > 4F-BUF > BUF. Fentanyl and BUF behaved as partial agonists for the β-arrestin 2 pathway, whereas 4F-BUF did not promote β-arrestin 2 recruitment. In vivo, we revealed sex differences in motor and cardiorespiratory impairments but not antinociception induced by BUF and 4F-BUF. Antalarmin alone was effective in blocking respiratory impairment induced by BUF in both sexes but not 4F-BUF. The combination of naloxone and antalarmin significantly enhanced naloxone reversal of the cardiorespiratory impairments induced by BUF and 4F-BUF in mice.

CONCLUSION AND IMPLICATIONS

In this study, we have uncovered a novel mechanism by which synthetic opioids induce respiratory depression, shedding new light on the role of CRF1 receptors in cardiorespiratory impairments by μ agonists.

Serum cytokines and inflammatory proteins in individuals with heroin use disorder: potential mechanistically based biomarkers for diagnosis

Opioid use disorders cause major morbidity and mortality, and there is a pressing need for novel mechanistic targets and biomarkers for diagnosis and prognosis. Exposure to mu-opioid receptor (MOR) agonists causes changes in cytokine and inflammatory protein networks in peripheral blood, and also in brain glia and neurons. Individuals with heroin use disorder (iHUD) show dysregulated levels of several cytokines in the blood. However, there is limited data on a comprehensive panel of such markers in iHUD versus healthy controls (HC), especially considered as a multi-target biomarker. We used a validated proximity extension assay for the relative quantification of 92 cytokines and inflammatory proteins in the serum of iHUD on medication-assisted therapy (MAT; n = 21), compared to HC (n = 24). Twenty-nine targets showed significant group differences (primarily iHUD>HC), surviving multiple comparison corrections (p = 0.05). These targets included 19 members of canonical cytokine families, including specific chemokines, interleukins, growth factors, and tumor necrosis factor (TNF)-related proteins. For dimensionality reduction, data from these 19 cytokines were entered into a principal component (PC) analysis, with PC1 scores showing significant group differences (iHUD > HC; p < 0.0001). A receiver-operating characteristic (ROC) curve analysis yielded an AUROC = 91.7% (p < 0.0001). This PC1 score remained a positive predictor of being in the HUD group in a multivariable logistic regression, that included select demographic/clinical variables. Overall, this study shows a panel of cytokines that differ significantly between iHUD and HC, providing a multi-target "cytokine biomarker score" for potential diagnostic purposes, and future examination of disease severity.

Fentanyl self-administration is accelerated by methamphetamine co-use and results in worsened hypodopaminergia in male, but not female rats

Combined use of fentanyl and methamphetamine (FENT + METH) has increased in recent years and has been documented in a growing number overdose deaths each year. The impact of FENT + METH on behavior and neurobiology is not well understood. In this study, male and female Long Evans rats were tested on a limited access, fixed ratio 1 self-administration schedule for increasing doses (1.25-5 μg/kg/infusion; iv) of fentanyl, with and without a single dose (0.1 mg/kg/infusion; iv) of methamphetamine, for 15 days. FENT + METH abolished dose responsiveness to fentanyl in all rats and accelerated intake in males, resulting in patterns of responding that may be more likely to result in adverse effects. Ex vivo slice voltammetry in the nucleus accumbens core showed decreases in dopamine release and reuptake (Vmax) following FENT + METH exposure, compared with saline, fentanyl, and methamphetamine alone groups at baseline parameters. Further, significant decreases in dopamine release were observed across a range of stimulation intensities following FENT + METH exposure. Overall, male and female rats displayed sex-specific behavioral and neurobiological responses to FENT + METH exposure, with males displaying increased vulnerability.

Sex disparities in outcome of medication-assisted therapy of opioid use disorder: Nationally representative study

Question

The opioid epidemic causes massive morbidity, and males have substantially greater overdose mortality rates than females. It is unclear whether there are sex-related disparities at different stages in the trajectory of opioid use disorders, in "real world" settings.

Goal

To determine sex disparities in non-medical opioid use (NMOU) at the end of outpatient medication-assisted treatment (MAT), using nationally representative data.

Design

Observational epidemiological study of publicly funded outpatient MAT programs in the national "Treatment episode data set-discharges" (TEDS-D) for 2019.

Participants

Persons aged ≥18 in their first treatment episode, in outpatient MAT for use of heroin or other opioids (N=11,549). The binary outcome was presence/absence of NMOU.

Results

In univariate analyses, males had significantly higher odds of NMOU, compared to females (odds ratio=1.27; Chi2 [df:1]=39.08; uncorrected p<0.0001; p=0.0041 after Bonferroni correction). A multivariable logistic regression detected a male>female odds ratio of 1.19 (95%CI=1.09-1.29; p<0.0001), adjusting for socio-demographic/clinical variables. Several specific conditions were revealed in which males had greater odds of NMOU compared to females (e.g., at ages 18-29 and 30-39; corrected p=0.012, or if they used opioids by inhalation; corrected p=0.0041).

Conclusions

This nationally representative study indicates that males have greater odds of NMOU in their first episode of MAT, indicating more unfavorable outcomes. The study reveals specific socio-demographic and clinical variables under which this sex disparity is most prominent.

Effect of chronic delivery of the NOP/MOR partial agonist AT-201 and NOP antagonist J-113397 on heroin relapse in a rat model of opioid maintenance

RATIONALE

The opioid crisis persists despite availability of effective opioid agonist maintenance treatments (methadone and buprenorphine). Thus, there is a need to advance novel medications for the treatment of opioid use and relapse.

OBJECTIVES

We recently modeled maintenance treatment in rats and found that chronic delivery of buprenorphine and the mu opioid receptor (MOR) partial agonist TRV130 decreases relapse to oxycodone seeking and taking. In contrast, chronic delivery of the buprenorphine analog BU08028 had mixed effects on different heroin relapse-related measures. Here, we tested the effect of the mixed nociceptin (NOP) receptor/MOR partial agonist AT-201 and the NOP receptor antagonist J-113397 on different heroin relapse-related measures.

METHODS

We trained male and female rats to self-administer heroin (6-h/d, 14-d) in context A and then implanted osmotic minipumps containing AT-201 (0, 3.8, or 12 mg/kg/d) or J-113397 (0, 12.6, or 40 mg/kg/d). Next, we tested the effect of chronic delivery of the compounds on (1) incubation of heroin seeking in a non-drug context B, (2) extinction responding reinforced by heroin-associated discrete cues in context B, (3) context A-induced reinstatement of heroin seeking, and (4) reacquisition of heroin self-administration in context A.

RESULTS

In females, AT-201 modestly increased reacquisition of heroin self-administration and J-113397 modestly decreased incubation of heroin seeking. The compounds had no effect on the other relapse-related measures in females, and no effect on any of the measures in males.

CONCLUSION

The NOP/MOR partial agonist AT-201 and the NOP antagonist J-113397 did not mimic buprenorphine's inhibitory effects on relapse in a rat model of opioid maintenance treatment.

Sex differences in opioid response: a role for the gut microbiome?

Opioid drugs have been long known to induce different responses in males compared to females, however, the molecular mechanisms underlying these effects are yet to be fully characterized. Recent studies have established a link between the gut microbiome and behavioral responses to opioids. Chronic opioid use is associated with gut dysbiosis, or microbiome disruptions, which is thought to contribute to altered opioid analgesia and reward processing. Gut microbiome composition and functioning have also been demonstrated to be influenced by sex hormones. Despite this, there is currently very little work investigating whether sex differences in the gut microbiome mediate sex-dependent responses to opioids, highlighting a critical gap in the literature. Here, we briefly review the supporting evidence implicating a potential role for the gut microbiome in regulating sexually dimorphic opioid response and identify areas for future research.

Opioid-Associated Nervous System Injuries

With the rise of the opioid epidemic, the practicing neurologist must recognize the patterns of a growing number of opioid-associated neurological injuries. This is in addition to the classic toxidrome of miosis, altered mental status, and respiratory depression, which must never be overlooked, as it is reversible and potentially lifesaving. Several other idiosyncratic syndromes due to opioid-related nervous system insults are defined by their characteristic imaging findings and portend variable functional recovery. Opioid toxicity can not only lead to brain injury, but also spinal cord and, rarely, peripheral nerve injury. As several newer synthetic opioids are undetectable by most assays, a low threshold to suspect opioid exposure must be maintained.

Evolution of an epidemic: Understanding the opioid epidemic in the United States and the impact of the COVID-19 pandemic on opioid-related mortality

We conduct this research with a two-fold aim: providing a quantitative analysis of the opioid epidemic in the United States (U.S.), and exploring the impact of the COVID-19 pandemic on opioid-related mortality. The duration and persistence of the opioid epidemic lends itself to the need for an overarching analysis with extensive scope. Additionally, studying the ramifications of these concurrent severe public health crises is vital for informing policies to avoid preventable mortality. Using data from CDC WONDER, we consider opioid-related deaths grouped by Census Region spanning January 1999 to October 2022 inclusive, and later add on a demographic component with gender-stratification. Through the lens of key events in the opioid epidemic, we build an interrupted time series model to reveal statistically significant drivers of opioid-related mortality. We then employ a counterfactual to approximate trends in the absence of COVID-19, and estimate excess opioid-related deaths (defined as observed opioid-related deaths minus projected opioid-related deaths) associated with the pandemic. According to our model, the proliferation of fentanyl contributed to sustained increases in opioid-related death rates across three of the four U.S. census regions, corroborating existing knowledge in the field. Critically, each region has an immediate increase to its opioid-related monthly death rate of at least 0.31 deaths per 100,000 persons at the start of the pandemic, highlighting the nationwide knock-on effects of COVID-19. There are consistent positive deviations from the expected monthly opioid-related death rate and a sizable burden from cumulative excess opioid-related deaths, surpassing 60,000 additional deaths nationally from March 2020 to October 2022, ∼70% of which were male. These results suggest that robust, multi-faceted measures are even more important in light of the COVID-19 pandemic to prevent overdoses and educate users on the risks associated with potent synthetic opioids such as fentanyl.

Associations among drug acquisition and use behaviors, psychosocial attributes, and opioid-involved overdoses

AIMS

This study sought to develop and assess an exploratory model of how demographic and psychosocial attributes, and drug use or acquisition behaviors interact to affect opioid-involved overdoses.

DESIGN

We conducted exploratory and confirmatory factor analysis (EFA/CFA) to identify a factor structure for ten drug acquisition and use behaviors. We then evaluated alternative structural equation models incorporating the identified factors, adding demographic and psychosocial attributes as predictors of past-year opioid overdose.

SETTING AND PARTICIPANTS

We used interview data collected for two studies recruiting opioid-misusing participants receiving services from a community-based syringe services program. The first investigated current attitudes toward drug-checking (N = 150). The second was an RCT assessing a telehealth versus in-person medical appointment for opioid use disorder treatment referral (N = 270).

MEASUREMENTS

Demographics included gender, age, race/ethnicity, education, and socioeconomic status. Psychosocial measures were homelessness, psychological distress, and trauma. Self-reported drug-related risk behaviors included using alone, having a new supplier, using opioids with benzodiazepines/alcohol, and preferring fentanyl. Past-year opioid-involved overdoses were dichotomized into experiencing none or any.

FINDINGS

The EFA/CFA revealed a two-factor structure with one factor reflecting drug acquisition and the second drug use behaviors. The selected model (CFI = .984, TLI = .981, RMSEA = .024) accounted for 13.1% of overdose probability variance. A latent variable representing psychosocial attributes was indirectly associated with an increase in past-year overdose probability (β = .234, p = .001), as mediated by the EFA/CFA identified latent variables: drug acquisition (β = .683, p < .001) and drug use (β = .567, p = .001). Drug use behaviors (β = .287, p = .04) but not drug acquisition (β = .105, p = .461) also had a significant, positive direct effect on past-year overdose. No demographic attributes were significant direct or indirect overdose predictors.

CONCLUSIONS

Psychosocial attributes, particularly homelessness, increase the probability of an overdose through associations with risky drug acquisition and drug-using behaviors. Further research is needed to replicate these findings with populations at high-risk of an opioid-related overdose to assess generalizability and refine the metrics used to assess psychosocial characteristics.

The lived experiences and treatment needs of women with opioid use disorder and posttraumatic stress symptoms: A mixed methods study

INTRODUCTION

Women show a gender-specific risk for co-occurring opioid use disorder (OUD) and posttraumatic stress disorder (PTSD). Expert groups have called for the development of integrated treatments for women with OUD/PTSD, but there remains limited information on such interventions.

METHODS

This mixed-methods study interviewed and surveyed 10 women with current or past OUD and co-occurring posttraumatic stress symptoms (PTSS) and 16 providers who work with these women. Interviews and surveys queried patient participants' and providers' experiences of OUD/PTSS and how to best design an integrated, trauma-focused treatment for OUD/PTSD.

RESULTS

Patient participants (90 % white, 90 % mothers, Mage = 45.70) met criteria for severe, lifetime OUD and 40 % met a provisional diagnosis for PTSD. Four themes emerged for participants' experiences of OUD/PTSS: 1) numerous stressors; 2) shame; 3) multiple motivations to use opioids; and 4) a cycle of trauma and opioid use. Four themes emerged regarding patient participants' perceptions on the development of an OUD/PTSD treatment: 1) mixed attitudes towards medications for OUD; 2) barriers to treatment (e.g., insufficient treatments and contextual factors); 3) treatment facilitators (e.g., social support); and 4) preferences in treatment (e.g., trauma-focused, gender-focused, family content, ambivalence around group therapy). Providers (Mage = 38.94) were primarily white women (76.5 %). Two themes emerged from their experiences working with women with OUD/PTSS: 1) perceiving women to use opioids to regulate emotions and 2) gender differences in trauma types. Three themes emerged for providers' perceptions on the development of an OUD/PTSD treatment: 1) barriers to treatment (e.g., chaotic lives, contextual factors, family); 2) treatment facilitators (e.g., trust and external motivations); and 3) desired treatment modifications (e.g., stabilization, early skills in therapy, flexibility in therapy, social supports, safety guidelines, and assistance in identifying an index trauma). Most participants (90.0 %) and providers (93.5 %) preferred working on OUD/PTSD symptoms simultaneously rather than separately.

CONCLUSIONS

Findings demonstrate the need to modify integrated treatments to meet the preferences of providers and women with OUD/PTSS and OUD/PTSD. Treatments should consider therapeutic content, structure, contextual factors, social support, and PTSD severity to enhance uptake and reach.

Combined treatment with naloxone and the alpha2 adrenoceptor antagonist atipamezole reversed brain hypoxia induced by a fentanyl-xylazine mixture in a rat model

Xylazine, a veterinary tranquillizer known by drug users as "Tranq", is being increasingly detected in people who overdose on opioid drugs, indicating enhanced health risk of fentanyl-xylazine mixtures. We recently found that xylazine potentiates fentanyl- and heroin-induced brain hypoxia and eliminates the rebound-like post-hypoxic oxygen increases. Here, we used oxygen sensors coupled with high-speed amperometry in rats of both sexes to explore the treatment potential of naloxone plus atipamezole, a selective α2-adrenoceptor antagonist, in reversing brain (nucleus accumbens) and periphery (subcutaneous space) hypoxia induced by a fentanyl-xylazine mixture. Pretreatment with naloxone (0.2 mg/kg, IV) fully blocked brain and peripheral hypoxia induced by fentanyl (20 μg/kg, IV), but only partially decreased hypoxia induced by a fentanyl-xylazine mixture. Pretreatment with atipamezole (0.25 mg/kg, IV) fully blocked the hypoxic effects of xylazine (1.0 mg/kg, IV), but not fentanyl. Pretreatment with atipamezole + naloxone was more potent than naloxone alone in blocking the hypoxic effects of the fentanyl-xylazine mixture. Both naloxone and naloxone + atipamezole, delivered at the peak of brain hypoxia (3 min post fentanyl-xylazine exposure), reversed the rapid initial brain hypoxia, but only naloxone + atipamezole decreased the prolonged weaker hypoxia. There were no sex differences in the effects of the different drugs and their combinations on brain and peripheral oxygen responses. Results indicate that combined treatment with naloxone and atipamezole is more effective than naloxone alone in reversing the hypoxic effects of fentanyl-xylazine mixtures. Naloxone + atipamezole treatment should be considered in preventing overdoses induced by fentanyl-xylazine mixtures in humans.

Naloxone prescription fills and use by patients treated for opioid use disorder by telehealth

Background

It is unknown how many people in treatment for opioid use disorder (OUD) have naloxone, use naloxone, and what their perceptions and barriers to obtaining it are.

Methods

This was a survey of patients treated in a large telehealth OUD program. Between December 6, 2023 and January 6, 2024, all patients who had access to the program's phone app (n=17,899 individuals, of whom 12,887 were in active treatment), were invited to complete an anonymous online survey.

Results

There were 701 individuals who completed the survey. Nearly all patients (n=693, 99%) knew what naloxone is, and the majority (n=601, 86%) knew how to administer it. A quarter of these patients (n=177, 25%) reported either having naloxone used on themselves or using it on someone else. 161 patients (23%) reported taking a naloxone training course. Of patients who recalled receiving a prescription, 72% (n=382) filled the prescription, and 85% (n=321) reported that insurance paid for all or part of it. If filled, the naloxone was reported as used by 30 (8%) patients. If not filled, reasons were: already had it (n=55, 37%), did not think it was needed (n=54, 37%) or too expensive (n=36, 23%). Patients who reported knowing how to administer naloxone (OR 2.63 (95% CI 1.35-5.00) were more likely to fill the prescription.

Conclusions

Patients prescribed naloxone in a telehealth treatment program filled the prescription 72% of the time, and when it was filled, 8% used the naloxone. Education and cost policy changes may reduce barriers to obtaining naloxone.

Serum cytokine and inflammatory markers in individuals with heroin use disorder: potential biomarkers for diagnosis and disease severity

Opioid use disorders cause major morbidity and mortality, and there is a pressing need for novel mechanistic targets and biomarkers for diagnosis and prognosis. Exposure to mu-opioid receptor (MOR) agonists causes changes in cytokine and inflammatory protein networks in peripheral blood, and also in brain glia and neurons. Individuals with heroin use disorder (iHUD) show dysregulated levels of several cytokines in blood. However, there is limited data on a comprehensive panel of such markers in iHUD versus healthy controls (HC), especially as a multi-target biomarker. We used a validated proximity extension assay for relative quantification of 92 cytokines and inflammatory proteins in serum of iHUD on medication assisted therapy (MAT; n=21), versus HC (n=24). Twenty-nine targets showed significant group differences (primarily iHUD>HC), surviving multiple comparison correction (p=0.05). This included 19 members of canonical cytokine families, including specific chemokines, interleukins, growth factors, and tumor necrosis factor (TNF)-related proteins. For dimensionality reduction, data from these 19 cytokines were entered into a principal component (PC) analysis, and PC1 scores were iHUD>HC (p<0.0001). A receiver-operating characteristic (ROC) curve analysis yielded an AUROC=91.7% (p<0.0001). This PC1 score remained a positive predictor of being in the HUD group in a multivariable logistic regression, which included demographic/clinical variables. Overall, this study shows a panel of cytokines that differ significantly between iHUD and HC, and provides a multi-target "cytokine biomarker score" for potential diagnostic purposes, and examination of disease severity.

Stimulant Drugs and Stimulant Use Disorder

The authors aim to summarize several key points of stimulant drugs and stimulant use disorder, including their indications, short-term and long-term adverse effects, current treatment strategies, and association with opioid medications. The global prevalence of stimulant use has seen annual increase in the last decade. Multiple studies have shown that stimulant use and stimulant use disorder are associated with a range of individual and public health issues. Stimulant misuse has led to a significant increase of overdose deaths in the United States.

Modeling methamphetamine use disorder in mammals: Sex differences in behavioral, biochemical, and transcriptional consequences

Methamphetamine (METH) is the most commonly misused amphetamine-type stimulant throughout the globe. METH is very rewarding, and its misuse can lead to a diagnosis of METH use disorder (MUD). Although METH use is observed in both sexes, there are, however, reported differences in the clinical manifestations of METH use and its consequences. These observations indicate the need for more research on the long-term sex-dependent consequences of METH taking in both preclinical and clinical settings. In effect, sex is a biological variable that can impact conclusions drawn from various basic and clinical studies. Thus, the present chapter provides a succinct review of the current state of the research on METH and its sex-associated consequences. In addition to behavioral and cognitive aspects of METH use, we discuss METH-induced changes in neurotransmitter systems and structures in the brain. Thus, the book chapter serves to highlight the significance of sex as a critical element that needs to be considered during discussions of novel therapeutic approaches to MUD.

A New Rat Study Suggests There May Be a Biologic Explanation for Higher Fentanyl Mortality in Men Than in Women

Could it be possible that we should give some weight to the contribution of biological differences as contributors to the greater fentanyl mortality in males than in females? Most current explanations for a sex difference are based largely on psychosocial and other non-physiologic contributions. Our recent findings suggest a biological contribution. This could have broad implications for the interpretation and prevention of fentanyl overdose deaths.

Associations among Drug Acquisition and Use Behaviors, Psychosocial Attributes, and Opioid-Involved Overdoses: A SEM Analysis

Aims

This study sought to develop and assess an exploratory model of how demographic and psychosocial attributes, and drug use or acquisition behaviors interact to affect opioid-involved overdoses.

Methods

We conducted exploratory and confirmatory factor analysis (EFA/CFA) to identify a factor structure for ten drug acquisition and use behaviors. We then evaluated alternative structural equation models incorporating the identified factors, adding demographic and psychosocial attributes as predictors of past-year opioid overdose. We used interview data collected for two studies recruiting opioid-misusing participants receiving services from a community-based syringe service program. The first investigated current attitudes toward drug-checking (N = 150). The second was an RCT assessing a telehealth versus in-person medical appointment for opioid use disorder treatment referral (N = 270). Demographics included gender, age, race/ethnicity, education, and socioeconomic status. Psychosocial measures were homelessness, psychological distress, and trauma. Self-reported drug-related risk behaviors included using alone, having a new supplier, using opioids with benzodiazepines/alcohol, and preferring fentanyl. Past-year opioid-involved overdoses were dichotomized into experiencing none or any.

Results

The EFA/CFA revealed a two-factor structure with one factor reflecting drug acquisition and the second drug use behaviors. The selected model (CFI = .984, TLI = .981, RMSEA = .024) accounted for 13.1% of overdose probability variance. A latent variable representing psychosocial attributes was indirectly associated with an increase in past-year overdose probability (β=.234, p = .001), as mediated by the EFA/CFA identified latent variables: drug acquisition (β=.683, p < .001) and drug use (β=.567, p = .001). Drug use behaviors (β=.287, p = .04) but not drug acquisition (β=.105, p = .461) also had a significant, positive direct effect on past-year overdose. No demographic attributes were significant direct or indirect overdose predictors.

Conclusions

Psychosocial attributes, particularly homelessness, increase the probability of an overdose through associations with risky drug acquisition and drug-using behaviors. To increase effectiveness, prevention efforts might address the interacting overdose risks that span multiple functional domains.

Neuroimmune Mechanisms of Opioid Use Disorder and Recovery: Translatability to Human Studies, and Future Research Directions

Opioid use disorder (OUD) is a major current cause of morbidity and mortality. Long-term exposure to short-acting opioids (MOP-r agonists such as heroin or fentanyl) results in complex pathophysiological changes to neuroimmune and neuroinflammatory functions, affected in part by peripheral mechanisms (e.g., cytokines in blood), and by neuroendocrine systems such as the hypothalamic-pituitary-adrenal (HPA) stress axis. There are important findings from preclinical models, but their role in the trajectory and outcomes of OUD in humans is not well understood. The goal of this narrative review is to examine available data on immune and inflammatory functions in persons with OUD, and to identify major areas for future research. Peripheral blood biomarker studies revealed a pro-inflammatory state in persons with OUD in withdrawal or early abstinence, consistent with available postmortem brain studies (which show glial activation) and diffusion tensor imaging studies (indicating white matter disruptions), with gradual abstinence-associated recovery. The mechanistic roles of these neuroimmune and neuroinflammatory changes in the trajectory of OUD (including recovery and medication management) cannot be examined practically with postmortem data. Collection of longitudinal data in larger-scale human cohorts would allow examination of these mechanisms associated with OUD stage and progression. Given the heterogeneity in presentation of OUD, a precision medicine approach integrating multi-omic peripheral biomarkers and comprehensive phenotyping, including neuroimaging, can be beneficial in risk stratification, and individually optimized selection of interventions for individuals who will benefit, and assessments under refractory therapy.