Changes in injecting versus smoking heroin, fentanyl, and methamphetamine among people who inject drugs in San Diego, California, 2020-2023.

BACKGROUND: Amidst an increasingly toxic drug supply in North America, people who inject drugs may be transitioning to smoking them. We aimed to assess changes in injecting and smoking opioids and methamphetamine among a cohort of people who inject drugs from San Diego, California. METHODS: Over five six-month periods spanning October 2020-April 2023, we assessed prevalence of injecting and smoking opioids or methamphetamine and whether participants used these drugs more frequently by smoking than injecting. Multivariable Poisson regression via generalized estimating equations was used to examine time trends. RESULTS: Of 362 participants, median age was 40 years; a minority were female (29%), Hispanic/Latinx/Mexican (45%), and housed (33%). Among this cohort, of whom 100% injected (and 84% injected and smoked) in period one (October 2020-April 2021), by period five (November 2022-April 2023), 34% only smoked, 59% injected and smoked, and 7% only injected. By period five, the adjusted relative risk (aRR) of injecting opioids was 0.41 (95% Confidence Interval [CI]: 0.33, 0.51) and the aRR for injecting methamphetamine was 0.50 (95% CI: 0.39, 0.63) compared to period one. Risks for smoking fentanyl rose significantly during period three (aRR=1.44, 95% CI: 1.06, 1.94), four (aRR=1.65, 95% CI: 1.24, 2.20) and five (aRR=1.90, 95% CI: 1.43, 2.53) compared to period one. Risks for smoking heroin and methamphetamine more frequently than injecting these drugs increased across all periods. CONCLUSIONS: Opioid and methamphetamine injection declined precipitously, with notable increases in smoking these drugs. Research is needed to understand the health consequences of these trends.

FDA Issues Warning About 'Gas Station Heroin'.

The highly addictive dietary supplement mimics opioid effects.

Pan-striatal reduction in the expression of the astrocytic dopamine transporter precedes the development of dorsolateral striatum dopamine-dependent incentive heroin seeking habits.

The emergence of compulsive drug-seeking habits, a hallmark feature of substance use disorder, has been shown to be predicated on the engagement of dorsolateral striatal control over behaviour. This process involves the dopamine-dependent functional coupling of the anterior dorsolateral striatum (aDLS) with the nucleus accumbens core, but the mechanisms by which this coupling occurs have not been fully elucidated. The striatum is tiled by a syncytium of astrocytes that express the dopamine transporter (DAT), the level of which is altered in individuals with heroin use disorder. Astrocytes are therefore uniquely placed functionally to bridge dopamine-dependent mechanisms across the striatum. Here we tested the hypothesis that exposure to heroin influences the expression of DAT in striatal astrocytes across the striatum before the development of DLS-dependent incentive heroin seeking habits. Using Western-blot, qPCR, and RNAscope™, we measured DAT protein and mRNA levels in whole tissue, culture and in situ astrocytes from striatal territories of rats with a well-established cue-controlled heroin seeking habit and rats trained to respond for heroin or food under continuous reinforcement. Incentive heroin seeking habits were associated with a reduction in DAT protein levels in the anterior aDLS that was preceded by a heroin-induced reduction in DAT mRNA and protein in astrocytes across the striatum. Striatal astrocytes were also shown to be susceptible to direct dopamine- and opioid-induced downregulation of DAT expression. These results suggest that astrocytes may critically regulate the striatal dopaminergic adaptations that lead to the development of incentive heroin seeking habits.

ß-caryophyllene inhibits heroin self-administration, but does not alter opioid-induced antinociception in rodents.

A growing body of research indicates that ß-caryophyllene (BCP), a constituent present in a large number of plants, possesses significant therapeutic properties against CNS disorders, including alcohol and psychostimulant use disorders. However, it is unknown whether BCP has similar therapeutic potential for opioid use disorders. In this study, we found that systemic administration of BCP dose-dependently reduced heroin self-administration in rats under an FR2 schedule of reinforcement and partially blocked heroin-enhanced brain stimulation reward in DAT-cre mice, maintained by optical stimulation of midbrain dopamine neurons at high frequencies. Acute administration of BCP failed to block heroin conditioned place preference (CPP) in male mice, but attenuated heroin-induced CPP in females. Furthermore, repeated dosing with BCP for 5 days facilitated the extinction of CPP in female but not male mice. In the hot plate assay, pretreatment with the same doses of BCP failed to enhance or prolong opioid antinociception. Lastly, in a substitution test, BCP replacement for heroin failed to maintain intravenous BCP self-administration, suggesting that BCP itself has no reinforcing properties. These findings suggest that BCP may have certain therapeutic effects against opioid use disorders with fewer unwanted side-effects by itself.

Adulterants present in the San Diego county fentanyl supply: a laboratory analysis of seized law enforcement samples.

BACKGROUND: The opioid overdose crisis is one of the worst public health crises ever to face the US and emerging evidence suggests its effects are compounded by the presence of drug adulterants. Here we report our efforts to characterize the adulterants present within the local fentanyl supply of San Diego County, obtained from undifferentiated drug samples seized by local law enforcement over the calendar year 2021. METHODS: Thirty-two participating local law enforcement agencies across San Diego submitted 4838 unknown individual illicit drug samples (total of 312 kg) to the San Diego County Sheriff's Department Regional Crime Laboratory for identification. RESULTS: Qualitative analysis of these samples via FTIR and GC-MS identified methamphetamine (38.7%), fentanyl (20.8%), diacetylmorphine (heroin) (10.2%), codeine (5.8%) and alprazolam (4.3%) as the most common illicit substances and the presence of 52 unique adulterants. The most common adulterants included 4-methylaminoantipyrine (4-MAAP) (10.9%), mannitol (9%), acetaminophen (8.5%), methamphetamine (4.2%), diacetylmorphine (heroin) (3.6%), tramadol (1.9%), and xylazine (1.7%). Several additional pharmacologically active adulterants and contaminants of interest were also identified. CONCLUSION: This analysis is vital for public health use and harm reduction efforts at the level of the individual consumer. Continued direct surveillance of the drug supply is necessary for the detection of potentially harmful adulterants that may pose serious threats to the public.

Fact vs. fiction: naloxone in the treatment of opioid-induced respiratory depression in the current era of synthetic opioids.

Opioid-induced respiratory depression (OIRD) deaths are ~80,000 a year in the US and are a major public health issue. Approximately 90% of fatal opioid-related deaths are due to synthetic opioids such as fentanyl, most of which is illicitly manufactured and distributed either on its own or as an adulterant to other drugs of abuse such as cocaine or methamphetamine. Other potent opioids such as nitazenes are also increasingly present in the illicit drug supply, and xylazine, a veterinary tranquilizer, is a prevalent additive to opioids and other drugs of abuse. Naloxone is the main treatment used to reverse OIRD and is available as nasal sprays, prefilled naloxone injection devices, and generic naloxone for injection. An overdose needs to be treated as soon as possible to avoid death, and synthetic opioids such as fentanyl are up to 50 times more potent than heroin, so the availability of new, higher-dose, 5-mg prefilled injection or 8-mg intranasal spray naloxone preparations are important additions for emergency treatment of OIRDs, especially by lay people in the community. Higher naloxone doses are expected to reverse a synthetic overdose more rapidly and the current formulations are ideal for use by untrained lay people in the community. There are potential concerns about severe withdrawal symptoms, or pulmonary edema from treatment with high-dose naloxone. However, from the perspective of first responders, the balance of risks would point to administration of naloxone at the dose required to combat the overdose where the risk of death is very high. The presence of xylazines as an adulterant complicates the treatment of OIRDs, as naloxone is probably ineffective, although it will reverse the respiratory depression due to the opioid. For these patients, hospitalization is particularly vital. Education about the benefits of naloxone remains important not only in informing people about how to treat emergency OIRDs but also how to obtain naloxone. A call to emergency services is also essential after administering naloxone because, although the patient may revive, they may overdose again later because of the short half-life of naloxone and the long-lasting potency of fentanyl and its analogs.

Development and validation of an LC-MS/MS method for quantifying diamorphine and its major metabolites 6-monoacetylmorphine, morphine, morphine-3-glucuronide, and morphine-6-glucuronide in human plasma.

Diamorphine, commonly known as heroin, is a semi-synthetic opioid analgesic. In the context of heroin-assisted treatment for opioid-dependent patients, diamorphine is mostly administered intravenously. However, recent attention has shifted towards intranasal administration as a better-tolerated alternative to the intravenous route. Here, we developed and validated a rapid bioanalytical method for the simultaneous quantification of diamorphine and its major metabolites 6-monoacetylmorphine, morphine, morphine-3-glucuronide, and morphine-6-glucuronide in human plasma using liquid chromatography-tandem mass spectrometry (LC-MS/MS). A straightforward protein precipitation extraction step was used for sample preparation. Chromatographic analyte separation was achieved using a Kinetex EVO C18 analytical column and a mobile phase gradient comprising an aqueous solution of ammonium hydrogen carbonate and methanol supplied with formic acid. Employing positive electrospray ionization and scheduled multiple reaction monitoring, we established a quantification range of 1-1,000 ng/mL for all analytes. Our validation results demonstrate a mean intra-assay accuracy of 91-106% and an intra-assay precision (CV) between 2 and 9% for all analytes and over three validation runs. The method exhibits a high extraction recovery (> 87%) and a negligible matrix effect (99-125%). Furthermore, no interferences with endogenous plasma compounds were detected. Lastly, we applied the method to assess the plasma concentrations of an opioid-dependent patient after the intranasal administration of diamorphine in a clinical study. In summary, we have successfully developed a rapid, highly reliable, and straightforward bioanalytical method for quantifying diamorphine and its metabolites in low amounts of clinical plasma samples.

Co-located Heroin Assisted Treatment within primary care: A preliminary analysis of the implications for healthcare access, cost, and treatment delivery in the UK.

BACKGROUND: The UK is experiencing its highest rate of drug related deaths in 25 years. Poor and inconsistent access to healthcare negatively impacts health outcomes for people who use drugs. Innovation in models of care which promote access and availability of physical treatment is fundamental. Heroin Assisted Treatment (HAT) is a treatment modality targeted at the most marginalised people who use drugs, at high risk of mortality and morbidity. The first service-provider initiated HAT service in the UK ran between October 2019 and November 2022 in Middlesbrough, England. The service was co-located within a specialist primary care facility offering acute healthcare treatment alongside injectable diamorphine. METHODS: Analysis of anonymised health records for healthcare costs (not including drug treatment) took place using descriptive statistics prior and during engagement with HAT, at both three (n=15) and six (n=12) months. Primary outcome measures were incidents of wound care, skin and soft tissue infections (SSTIs), overdose (OD) events, unplanned overnight stays in hospital, treatment engagement (general and within hospital care settings) and ambulance incidents. Secondary outcome measures were costs associated with these events. RESULTS: A shift in healthcare access for participants during HAT engagement was observed. HAT service attendance appeared to support health promoting preventative care, and reduce reactive reliance on emergency healthcare systems. At three and six months, engagement for preventative wound care and treatment for SSTIs increased at the practice. Unplanned emergency healthcare interactions for ODs, overnight hospital stays, serious SSTIs, and ambulance incidents reduced, and there was an increase in treatment engagement (i.e. a reduction in appointments which were not engaged with). There was a decrease in treatment engagement in hospital settings. Changes in healthcare utilisation during HAT translated to a reduction in healthcare costs of 58% within six months compared to the same timeframe from the period directly prior to commencing HAT. CONCLUSION: This exploratory study highlights the potential for innovative harm reduction interventions such as HAT, co-located with primary care services, to improve healthcare access and engagement for a high-risk population. Increased uptake of primary healthcare services translated to reductions in emergency healthcare use and associated costs. Although costs of HAT provision are substantial, the notable cost-savings in health care should be an important consideration in service implementation planning.

Inhibition of SIRT1 in the nucleus accumbens attenuates heroin addiction-related behavior by decreasing D1 neuronal autophagy.

This study aimed to investigate the effects of SIRT1 modulation on heroin addiction-like behavior and its possible biological mechanisms. Wild-type C57BL/6J and Sirt1loxp/loxp D1-Cre mice were used in this experiment, and Sirt1 loxp/loxp D1-Cre(-) mice were used as a control for conditional knockout mice. Mice were divided into saline control and heroin-dependent groups. Behavioral methods were used to record the withdrawal response, conditioned place preference (CPP) changes, and open field test results. Transmission electron microscopy (TEM) was used to observe the structure of autophagosomes in nucleus accumbens (NAc) neurons. The expression of SIRT1 and autophagy-related proteins and genes, such as LC3Ⅱ, ATG5 , and ATG7 , was detected in the NAc of each mouse group via western blot, real-time quantitative PCR (qPCR) analyzes, and immunofluorescence. The results of this experiment showed that compared with the saline group, mice in the wild-type heroin-dependent group showed marked withdrawal symptoms, with more autophagosomes observed in NAc via TEM. Compared with wild-type and Sirt1loxp/loxp D1-Cre(-) heroin-dependent groups, CPP formation was found to be reduced in the conditional knockout mouse group, with a significant decrease in spontaneous activity. Western blot, qPCR, and immunofluorescence results indicated that the expression of LC3Ⅱ, ATG-5, and ATG-7 was significantly reduced in the NAc of the Sirt1loxp/loxp D1-Cre(+) group. It was still, however, higher than that in the saline control group. These results suggest that inhibition of Sirt1 expression may prevent heroin-induced addiction-related behaviors via reducing D1 neuronal autophagy.

Detection of contraband drugs in forensic-correctional mental health services using TeknoScan-a gas chromatography tool.

Substance misuse is a major problem among individuals involved in forensic-correctional mental health services. Urine drug screening detects substance use and deters the entry of contraband into forensic-correctional units, albeit with limitations. For example, a point-of-care urine sample may not be possible and patients can alter or substitute samples to avoid detection, highlighting the role of ancillary tools to detect contraband substances. This study describes the pattern and types of substances detected from environmental samples using a gas chromatographic analyzer (TeknoScan TSI3000) in forensic-correctional populations to model the benefits of similar tools in similar settings. Samples collected over 18 months (January 2020 to June 2021) by trained staff members using the machine were reviewed. During this period, 217 environmental samples were recorded, and 66 (30%) samples were positive for contraband substances, including tetrahydrocannabinol (25%), methamphetamines (19%), and cocaine (16%). Other substances detected include methylene-dioxymethamphetamine, heroin, morphine, lysergic acid diethylamide, tramadol, and methyl-benzoate. Fewer positive samples were detected, especially during the time corresponding with the COVID-19 restriction on the forensic units. TeknoScan was beneficial as an ancillary tool to detect and deter contraband substances. It also provided evidence for risk management. Adequate training is needed for the successful implementation of the tool.

Long-access heroin self-administration induces region specific reduction of grey matter volume and microglia reactivity in the rat.

In opioid use disorder (OUD) patients, a decrease in brain grey matter volume (GMV) has been reported. It is unclear whether this is the consequence of prolonged exposure to opioids or is a predisposing causal factor in OUD development. To investigate this, we conducted a structural MRI longitudinal study in NIH Heterogeneous Stock rats exposed to heroin self-administration and age-matched naïve controls housed in the same controlled environment. Structural MRI scans were acquired before (MRI1) and after (MRI2) a prolonged period of long access heroin self-administration resulting in escalation of drug intake. Heroin intake resulted in reduced GMV in various cortical and sub-cortical brain regions. In drug-naïve controls no difference was found between MRI1 and MRI2. Notably, the degree of GMV reduction in the medial prefrontal cortex (mPFC) and the insula positively correlated with the amount of heroin consumed and the escalation of heroin use. In a preliminary gene expression analysis, we identified a number of transcripts linked to immune response and neuroinflammation. This prompted us to hypothesize a link between changes in microglia homeostasis and loss of GMV. For this reason, we analyzed the number and morphology of microglial cells in the mPFC and insula. The number of neurons and their morphology was also evaluated. The primary motor cortex, where no GMV change was observed, was used as negative control. We found no differences in the number of neurons and microglia cells following heroin. However, in the same regions where reduced GMV was detected, we observed a shift towards a rounder shape and size reduction in microglia, suggestive of their homeostatic change towards a reactive state. Altogether these findings suggest that escalation of heroin intake correlates with loss of GMV in specific brain regions and that this phenomenon is linked to changes in microglial morphology.

The effect of opioid use on traffic fatalities.

We use a difference-in-differences design to study the effect of opioid use on traffic fatalities. Following Alpert et al., we focus on the 1996 introduction and marketing of OxyContin, and we examine its long-term impacts on traffic fatalities involving Schedule II drugs or heroin. Based on the national fatal vehicle crash database, we find that the states heavily targeted by the initial marketing of OxyContin (i.e., non-triplicate states) experienced 2.4 times more traffic fatalities (1.6 additional deaths per million individuals) involving Schedule II drugs or heroin during 2011-2019, when overdose deaths from heroin and fentanyl became more prominent. We find no difference in traffic fatalities until after the mid-2000s between states with and without a triplicate prescription program. The effect is mainly concentrated in fatal crashes with drug involvement of drivers ages between 25 and 44. Our results highlight additional long-term detrimental consequences of the introduction and marketing of OxyContin.

The influence of transformations in supply on methamphetamine initiation among people injecting opioids in the United States.

BACKGROUND: Co-use of methamphetamine (MA) and opioids (pharmaceutical pills, heroin and fentanyls) has increased in the United States and is represented in rising mortality. Although coinciding with the import of low cost, high potency and purity methamphetamine, the relationship between supply and demand in propelling this polydrug use is not well understood. We consider the influence of macro changes in supply on the uptake of opioid and methamphetamine co-use by injection at the level of individual drug and injection initiation in West Virginia, a state which leads the US in drug overdose mortality. METHOD: We recruited n = 30 people for semi-structured interviews who self-reported injecting heroin/fentanyl and using methamphetamine by any route at a West Virginia syringe service program and through snowball sampling. Interviews were recorded and transcripts analyzed using a thematic approach. Ethnographic observation was also conducted and recorded in fieldnotes. Sequence of substance and mode of use initiation and use trajectories for opioids and stimulants were charted for each participant. RESULTS: A clear pattern of individual drug initiation emerged that matched each successive supply wave of the US overdose epidemic: 25 participants had initiated opioid use with pills, followed by heroin, often mixed with/replaced by fentanyl, and subsequently added methamphetamine use. For participants, the supply and consumption of opioid analgesics had set in motion a series of steps leading to the addition of stimulant injection to existing opioid injecting repertoires. Unlike other studies that have found a birth cohort effect in patterns of initiation, participants showed the same sequence across age groups. Considerations of economy, availability, dependence, tolerance and the erosion of taboos that marked transitions from opioid pills to heroin injection influenced these subsequent trajectories in novel ways. The form, timing and extent of opioid and stimulant consumption was influenced by four stages of the changing drug supply, which in turn reflected back on demand. CONCLUSION: Transformations in the social meaning and supply of methamphetamine enabled these transitions while other desired, non-injectable drugs were difficult to obtain. We discuss policy implications of injectable drugs' market dominance at this location and possible interventions.

Evaluation of heroin-assisted treatment in Norway: protocol for a mixed methods study.

BACKGROUND: Opioid agonist treatment (OAT) for patients with opioid use disorder (OUD) has a convincing evidence base, although variable retention rates suggest that it may not be beneficial for all. One of the options to include more patients is the introduction of heroin-assisted treatment (HAT), which involves the prescribing of pharmaceutical heroin in a clinical supervised setting. Clinical trials suggest that HAT positively affects illicit drug use, criminal behavior, quality of life, and health. The results are less clear for longer-term outcomes such as mortality, level of function and social integration. This protocol describes a longitudinal evaluation of the introduction of HAT into the OAT services in Norway over a 5-year period. The main aim of the project is to study the individual, organizational and societal effects of implementing HAT in the specialized healthcare services for OUD. METHODS: The project adopts a multidisciplinary approach, where the primary cohort for analysis will consist of approximately 250 patients in Norway, observed during the period of 2022-2026. Cohorts for comparative analysis will include all HAT-patients in Denmark from 2010 to 2022 (N = 500) and all Norwegian patients in conventional OAT (N = 8300). Data comes from individual in-depth and semi-structured interviews, self-report questionnaires, clinical records, and national registries, collected at several time points throughout patients' courses of treatment. Qualitative analyses will use a flexible inductive thematic approach. Quantitative analyses will employ a wide array of methods including bi-variate parametric and non-parametric tests, and various forms of multivariate modeling. DISCUSSION: The project's primary strength lies in its comprehensive and longitudinal approach. It has the potential to reveal new insights on whether pharmaceutical heroin should be an integral part of integrated conventional OAT services to individually tailor treatments for patients with OUD. This could affect considerations about drug treatment even beyond HAT-specific topics, where an expanded understanding of why some do not succeed with conventional OAT will strengthen the knowledge base for drug treatment in general. Results will be disseminated to the scientific community, clinicians, and policy makers. TRIAL REGISTRATION: The study was approved by the Norwegian Regional Committee for Medical and Health Research Ethics (REK), ref.nr.:195733.

State-level variation in distribution of oxycodone and opioid-related deaths from 2000 to 2021: an ecological study of ARCOS and CDC WONDER data in the USA.

OBJECTIVES: This study aims to characterise oxycodone's distribution and opioid-related overdoses in the USA by state from 2000 to 2021. DESIGN: This is an observational study. SETTING: More than 80 000 Americans died of an opioid overdose in 2021 as the USA continues to struggle with an opioid crisis. Prescription opioids play a substantial role, introducing patients to opioids and providing a supply of drugs that can be redirected to those seeking to misuse them. METHODS: The Drug Enforcement Administration annual summary reports from the Automation of Reports and Consolidated Orders System provided weights of oxycodone distributed per state by business type (pharmacies, hospitals and practitioners). Weights were converted to morphine milligram equivalents (MME) per capita and normalised for population. The Centers for Disease Control and Prevention Wide-ranging ONline Data for Epidemiologic Research provided mortality data for heroin, other opioids, methadone, other synthetic narcotics and other/unspecified narcotics. RESULTS: There was a sharp 280.13% increase in total MME/person of oxycodone from 2000 to 2010, followed by a slower 54.34% decrease from 2010 to 2021. Florida (2007-2011), Delaware (2003-2020) and Tennessee (2012-2021) displayed consistent and substantial elevations in combined MME/person compared with other states. In the peak year (2010), there was a 15-fold difference between the highest and lowest states. MME/person from only pharmacies, which constituted >94% of the total, showed similar results. Hospitals in Alaska (2000-2001, 2008, 2010-2021), Colorado (2008-2021) and DC (2000-2011) distributed substantially more MME/person over many years compared with other states. Florida stood out in practitioner-distributed oxycodone, with an elevation of almost 15-fold the average state from 2006 to 2010. Opioid-related deaths increased +806% from 2000 to 2021, largely driven by heroin, other opioids and other synthetic narcotics. CONCLUSIONS: Oxycodone distribution across the USA showed marked differences between states and business types over time. Investigation of opioid policies in states of interest may provide insight for future actions to mitigate opioid misuse.

Full Characterisation of Heroin Samples Using Infrared Spectroscopy and Multivariate Calibration.

The analysis of heroin samples, before use in the protected environment of user centra, could be a supplementary service in the context of harm reduction. Infrared spectroscopy hyphenated with multivariate calibration could be a valuable asset in this context, and therefore 125 heroin samples were collected directly from users and analysed with classical chromatographic techniques. Further, Mid-Infrared spectra were collected for all samples, to be used in Partial Least Squares (PLS) modelling, in order to obtain qualitative and quantitative models based on real live samples. The approach showed that it was possible to identify and quantify heroin in the samples based on the collected spectral data and PLS modelling. These models were able to identify heroin correctly for 96% of the samples of the external test set with precision, specificity and sensitivity values of 100.0, 75.0 and 95.5%, respectively. For regression, a root mean squared error of prediction (RMSEP) of 0.04 was obtained, pointing at good predictive properties. Furthermore, during mass spectrometric screening, 10 different adulterants and impurities were encountered. Using the spectral data to model the presence of each of these resulted in performant models for seven of them. All models showed promising correct-classification rates (between 92 and 96%) and good values for sensitivity, specificity and precision. For codeine and morphine, the models were not satisfactory, probably due to the low concentration of these impurities as a consequence of acetylation. For methacetin, the approach failed.

Rebuilding the behavioral inhibition circuit to prevent opioid relapse.

Failure in behavioral suppression is a key feature in substance use disorders, potentially leading to compulsive drug seeking and relapse. In this issue of Neuron, Paniccia et al.1 elucidated a heroin-damaged paraventricular nucleus of the thalamus (PVT)-accumbal circuit and how recovery of PVT function could prevent heroin relapse.

The dynamics of heroin and illicit opioid use disorder, casual use, treatment, and recovery: A mathematical modeling analysis.

A leading crisis in the United States is the opioid use disorder (OUD) epidemic. Opioid overdose deaths have been increasing, with over 100,000 deaths due to overdose from April 2020 to April 2021. This paper presents a mathematical model to address illicit OUD (IOUD), initiation, casual use, treatment, relapse, recovery, and opioid overdose deaths within an epidemiological framework. Within this model, individuals remain in the recovery class unless they relapse back to use and due to the limited availability of specialty treatment facilities for individuals with OUD, a saturation treatment function was incorporated. Additionally, a casual user class and its corresponding specialty treatment class were incorporated. We use both heroin and all-illicit opioids datasets to find parameter estimates for our models. Bistability of equilibrium solutions was found for realistic parameter values for the heroin-only dataset. This result implies that it would be beneficial to increase the availability of treatment. An alarming effect was discovered about the high overdose death rate: by 2046, the disorder-free equilibrium would be the only stable equilibrium. This consequence is concerning because it means the epidemic would end due to high overdose death rates. The IOUD model with a casual user class, its sensitivity results, and the comparison of parameters for both datasets, showed the importance of not overlooking the influence that casual users have in driving the all-illicit opioid epidemic. Casual users stay in the casual user class longer and are not going to treatment as quickly as the users of the heroin epidemic. Another result was that the users of the all-illicit opioids were going to the recovered class by means other than specialty treatment. However, the change in the relapse rate has more of an influence for those individuals than in the heroin-only epidemic. The results above from analyzing this model may inform health and policy officials, leading to more effective treatment options and prevention efforts.

Regulation of histone acetylation by garcinol blocks the reconsolidation of heroin-associated memory.

Drug-associated long-term memories underlie substance use disorders, including heroin use disorder (HUD), which are difficult to eliminate through existing therapies. Addictive memories may become unstable when reexposed to drug-related cues and need to be stabilized again through protein resynthesis. Studies have shown the involvement of histone acetylation in the formation and reconsolidation of long-term drug-associated memory. However, it remains unknown whether and how histone acetyltransferases (HAT), the essential regulators of histone acetylation, contribute to the reconsolidation of heroin-associated memories. Herein, we investigated the function of HAT in the reconsolidation concerning heroin-conditioned memory by using a rat self-administration model. Systemic administration of the HAT inhibitor garcinol inhibited cue and heroin-priming induced reinstatement of heroin seeking, indicating the treatment potential of garcinol for relapse prevention.