Electroluminescence as a Probe of Strong Exciton-Plasmon Coupling in Few-Layer WSe2.

The manipulation of coupled quantum excitations is of fundamental importance in realizing novel photonic and optoelectronic devices. We use electroluminescence to probe plasmon-exciton coupling in hybrid structures consisting of a nanoscale plasmonic tunnel junction and few-layer two-dimensional transition-metal dichalcogenide transferred onto the junction. The resulting hybrid states act as a novel dielectric environment that affects the radiative recombination of hot carriers in the plasmonic nanostructure. We determine the plexcitonic spectrum from the electroluminescence and find Rabi splittings exceeding 50 meV in the strong coupling regime. Our experimental findings are supported by electromagnetic simulations that enable us to explore systematically and in detail the emergence of plexciton polaritons as well as the polarization characteristics of their far-field emission. Electroluminescence modulated by plexciton coupling provides potential applications for engineering compact photonic devices with tunable optical and electrical properties.

Brownian Motion Governs the Plasmonic Enhancement of Colloidal Upconverting Nanoparticles.

Upconverting nanoparticles are essential in modern photonics due to their ability to convert infrared light to visible light. Despite their significance, they exhibit limited brightness, a key drawback that can be addressed by combining them with plasmonic nanoparticles. Plasmon-enhanced upconversion has been widely demonstrated in dry environments, where upconverting nanoparticles are immobilized, but constitutes a challenge in liquid media where Brownian motion competes against immobilization. This study employs optical tweezers for the three-dimensional manipulation of an individual upconverting nanoparticle, enabling the exploration of plasmon-enhanced upconversion luminescence in water. Contrary to expectation, experiments reveal a long-range (micrometer scale) and moderate (20%) enhancement in upconversion luminescence due to the plasmonic resonances of gold nanostructures. Comparison between experiments and numerical simulations evidences the key role of Brownian motion. It is demonstrated how the three-dimensional Brownian fluctuations of the upconverting nanoparticle lead to an "average effect" that explains the magnitude and spatial extension of luminescence enhancement.

Intersections between syndemic conditions and stages along the continuum of overdose risk among women who inject drugs in Mexicali, Mexico.

BACKGROUND: Research on women who inject drugs is scarce in low- and middle-income countries. Women experience unique harms such as sexism and sexual violence which translate into negative health outcomes. The present work aims to provide insight into the experiences of women who inject drugs at the US-Mexico border to identify social and health-related risk factors for overdose to guide harm reduction interventions across the Global South. METHODS: We recruited 25 women ≥ 18 years of age accessing harm reduction and sexual health services at a non-governmental harm reduction organization, "Verter", in Mexicali, Mexico. We employed purposeful sampling to recruit women who inject drugs who met eligibility criteria. We collected quantitative survey data and in-depth interview data. Analyses of both data sources involved the examination of descriptive statistics and thematic analysis, respectively, and were guided by the syndemic and continuum of overdose risk frameworks. RESULTS: Survey data demonstrated reports of initiating injection drug use at a young age, experiencing homelessness, engaging in sex work, being rejected by family members, experiencing physical violence, injecting in public spaces, and experiencing repeated overdose events. Interview data provided evidence of stigma and discrimination toward women, a lack of safe spaces and support systems, risk of overdose-related harms, sexual violence, and the overall need for harm reduction services. CONCLUSION: Women who inject drugs in Mexicali describe experiences of violence, overdose, and public injecting. Women are particularly vulnerable in the Mexicali context, as this area faces a noticeable lack of health and social services. Evidenced-based harm reduction strategies such as safe consumption sites and overdose prevention strategies (e.g., naloxone distribution and training) may benefit this population. Evidence from local organizations could help close the gap in service provision in low-resource settings like Mexico, where government action is almost nonexistent.

Time-Series Analysis of Fentanyl Concentration in the Unregulated Opioid Drug Supply in a Canadian Setting.

North America has been contending with an unregulated street drug supply in which opioids are often adulterated with illicitly manufactured fentanyl. The unpredictability of composition may result in an increased risk of overdose due to unexpected elevated concentrations of the high-potency drug. Using data from a community-based drug-checking project, we evaluated trends in fentanyl concentration of illicit opioids in the context of an overdose epidemic. Using a quantification model for fentanyl hydrochloride, historical Fourier-transform infrared spectra from opioid drug-checking samples were analyzed to determine fentanyl concentrations. Median monthly fentanyl concentrations were plotted, and polynomial and autoregressive time-series analyses were performed to examine trends over time. A total of 3,621 fentanyl-positive samples were included in the study, spanning November 2017 to December 2019. Monthly median fentanyl concentrations ranged from 4.5% to 10.4%. Time-series analyses indicated that a third-degree polynomial model fit the data well (R2 = 0.639), suggesting a cyclical pattern in median concentration over time. Notably, absolute variance in fentanyl concentration decreased by an average 0.1% per month (P < 0.001). Future research should explore the relationship between fentanyl concentration and overdose to identify potential targeted harm-reduction interventions that can respond to changes in observed fentanyl concentration.

Municipal police support for harm reduction services in officer-led referrals of people who inject drugs in Tijuana, Mexico.

BACKGROUND: Police constitute a structural determinant of health and HIV risk of people who inject drugs (PWID), and negative encounters with law enforcement present significant barriers to PWID access to harm reduction services. Conversely, police may facilitate access via officer-led referrals, potentiating prevention of HIV, overdose, and drug-related harms. We aimed to identify police characteristics associated with support for officer-led referrals to addiction treatment services and syringe service programs (SSP). We hypothesized that officers who believe harm reduction services are contradictory to policing priorities in terms of safety and crime reduction will be less likely to support police referrals. METHODS: Between January and June 2018, police officers (n = 305) in Tijuana, Mexico, completed self-administered surveys about referrals to harm reduction services during the 24-month follow-up visit as part of the SHIELD police training and longitudinal cohort study. Log-binomial regression was used to estimate adjusted prevalence ratios and model policing characteristics and attitudes related to officers' support for including addiction treatment and SSP in referrals. RESULTS: Respondents were primarily male (89%), patrol officers (86%) with a median age of 38 years (IQR 33-43). Overall, 89% endorsed referral to addiction services, whereas 53% endorsed SSP as acceptable targets of referrals. Officers endorsing addiction services were less likely to be assigned to high drug use districts (adjusted prevalence ratio [APR] = 0.50, 95% CI 0.24, 1.08) and more likely to agree that methadone programs reduce crime (APR = 4.66, 95% CI 2.05, 9.18) than officers who did not support addiction services. Officers endorsing SSPs were younger (adjusted prevalence ratio [APR] = 0.96 95% CI 0.93, 0.98), less likely to be assigned to high drug use districts (APR = 0.50, 95% CI 0.29, 0.87), more likely to believe that methadone programs reduce crime (APR = 2.43, 95% CI 1.30, 4.55), and less likely to believe that SSPs increase risk of needlestick injury for police (APR = 0.44, 0.27, 0.71). CONCLUSIONS: Beliefs related to the occupational impact of harm reduction services in terms of officer safety and crime reduction are associated with support for referral to related harm reduction services. Efforts to deflect PWID from carceral systems toward harm reduction by frontline police should include measures to improve officer knowledge and attitudes about harm reduction services as they relate to occupational safety and law enforcement priorities. TRIAL REGISTRATION: NCT02444403.

The utility of visual appearance in predicting the composition of street opioids.

Background: With the emergence of unregulated fentanyl, people who use unregulated opioids are increasingly relying on appearance in an effort to ascertain the presence of fentanyl and level of drug potency. However, the utility of visual inspection to identify drug composition in the fentanyl era has not been assessed. Methods: We assessed client expectation, appearance, and composition of street drug samples being presented for drug checking. Results of a visual screening test were compared to fentanyl immunoassay strip testing. We calculated sensitivity, specificity and likelihood ratios (LR) to assess the accuracy of the common assumption that samples with a "pebbles" appearance contain fentanyl. Results: In total, of the 2502 unregulated opioid samples tested, 1820 (73.5%) appeared as "pebbles", of which 1729 (95.0%) tested positive for fentanyl for a sensitivity of 75.9% (95% Confidence Interval [CI]: 74.2-77.6) and specificity of 59.4% (95%CI: 57.5-61.3). Although, the odds of samples containing fentanyl was 4.60 (95%CI: 3.47-6.11) times higher among pebbles samples compared to non-pebble samples, the positive LR for pebbles to contain fentanyl was only 1.87 (CI: 1.59-2.19). The negative LR was more useful at 0.41 (95% CI: 0.36-0.46). Conclusions: A positive screening test for pebbles is not strongly enough associated to be used as a proxy for detecting fentanyl. While the absence of the appearance of pebbles does somewhat reduce the likelihood of fentanyl being present in a given sample, the high prevalence of fentanyl and fentanyl analogues in the drug supply and the risks of consumption are such that public health providers should routinely advise people who use unregulated opioids against solely relying on visual characteristics of drugs as a harm reduction strategy.

Factors associated with drug checking service utilization among people who use drugs in a Canadian setting.

BACKGROUND: The United States and Canada are amidst an opioid overdose crisis, with the Canadian province of British Columbia (BC) among the hardest hit. In response, drug checking services (DCS) have been introduced in this setting as a novel pilot harm reduction intervention though little is known about usage rates. Therefore, we sought to identify factors associated with drug checking uptake among people who use drugs (PWUD) in Vancouver, BC. METHODS: Data were derived from three ongoing prospective cohort studies of PWUD in Vancouver between June and November 2018. Multivariable logistic regression was used to determine factors associated with self-reported DCS utilization in the past 6 months among participants at high risk of fentanyl exposure (i.e., those self-reporting illicit opioid use or testing positive for fentanyl via urine drug screen). RESULTS: Among 828 eligible participants, including 451 (55%) males, 176 (21%) reported recent use of DCS. In multivariable analyses, factors significantly associated with DCS utilization included: homelessness (Adjusted Odds Ratio [AOR] 1.47; 95% Confidence Interval [CI] 1.01-2.13) and involvement in drug dealing (AOR 1.59; 95% CI 1.05-2.39). CONCLUSIONS: In our sample of PWUD, uptake of DCS was low, although those who were homeless, a sub-population known to be at a heightened risk of overdose, were more likely to use the services. Those involved in drug dealing were also more likely to use the services, which may imply potential for improving drug market safety. Further evaluation of drug checking is warranted.

Interactive Versus Video-Based Training of Police to Communicate Syringe Legality to People Who Inject Drugs: The SHIELD Study, Mexico, 2015-2016.

Objectives. To assess how instructional techniques affect officers' intent to communicate syringe legality during searches in Tijuana, Mexico, where pervasive syringe confiscation potentiates risk of HIV and HCV among people who inject drugs (PWID) and of occupational needle-stick injury among police. Methods. Using the SHIELD (Safety and Health Integration in the Enforcement of Laws on Drugs) model, Tijuana police underwent training to encourage communication of syringe possession legality to PWID. Trainees received either passive video or interactive role-play exercise on safer search techniques. We used logistic regression to assess the training's impact on self-reported intent to communicate syringe legality by training type and gender. Results. Officers (n = 1749) were mostly men (86%) assigned to patrol (84%). After the training, intent to communicate the law improved markedly: from 20% to 39% (video group) and 20% to 58% (interactive group). Gender and training type significantly predicted intent to communicate syringe legality. Male and female officers' adjusted odds ratios in the interactive group were 5.37 (95% confidence interval [CI] = 4.56, 6.33) and 9.16 (95% CI = 5.88, 14.28), respectively, after the training. Conclusions. To more effectively persuade police to endorse harm reduction and occupational safety practices, police trainings should include interactive elements.

Improving police conceptual knowledge of Mexico's law on cannabis possession: Findings from an assessment of a police education program.

BACKGROUND AND OBJECTIVES: Policing practices do not reflect recent decriminalization of drug possession in Mexico. We assessed knowledge of cannabis law as part of a police education program (PEP) post-drug law reform in Tijuana. METHODS: Officers took pre-/post-PEP surveys; random subsample (n = 759) received follow-up assessments. Longitudinal logistic regression (pre-, post-, 3-months post-PEP) measured knowledge of cannabis law. RESULTS: PEP increased conceptual knowledge of cannabis law from baseline to post-training (AOR = 56.1, CI: 41.0-76.8) and 3 months post-PEP (AOR = 11.3, CI: 9.0-14.2). CONCLUSION AND SCIENTIFIC SIGNIFICANCE: PEPs improve police knowledge of cannabis law. Reforms should be bundled with PEPs to improve policy implementation. (Am J Addict 2018;XX:XX-XX).

Factors associated with extrajudicial arrest for syringe possession: results of a department-wide survey of municipal police in Tijuana, Mexico.

BACKGROUND: Mexican law permits syringe purchase and possession without prescription. Nonetheless, people who inject drugs (PWID) frequently report arrest for syringe possession. Extrajudicial arrests not only violate human rights, but also significantly increase the risk of blood-borne infection transmission and other health harms among PWID and police personnel. To better understand how police practices contribute to the PWID risk environment, prior research has primarily examined drug user perspectives and experiences. This study focuses on municipal police officers (MPOs) in Tijuana, Mexico to identify factors associated with self-reported arrests for syringe possession. METHODS: Participants were active police officers aged ≥18 years, who completed a self-administered questionnaire on knowledge, attitudes and behaviors related to occupational safety, drug laws, and harm reduction strategies. Univariable and multivariable logistic regression was used to identify correlates of recent syringe possession arrest. RESULTS: Among 1044 MPOs, nearly half (47.9%) reported always/sometimes making arrests for syringe possession (previous 6mo). Factors independently associated with more frequent arrest included being male (Adjusted Odds Ratio [AOR] = 1.62; 95% Confidence Interval [95% CI] =1.04-2.52; working in a district along Tijuana River Canal (where PWID congregate) (AOR = 2.85; 95%CI = 2.16-3.77); having recently experienced a physical altercation with PWID (AOR = 2.83; 95% CI = 2.15-3.74); and having recently referred PWID to social and health services (AOR = 1.97; 95% CI = 1.48-2.61). Conversely, odds were significantly lower among officers reporting knowing that syringe possession is legal (AOR = 0.61; 95% CI = 0.46-0.82). CONCLUSIONS: Police and related criminal justice stakeholders (e.g., municipal judges, prosecutors) play a key role in shaping PWID risk environment. Findings highlight the urgent need for structural interventions to reduce extra-judicial syringe possession arrests. Police training, increasing gender and other forms of diversity, and policy reforms at various governmental and institutional levels are necessary to reduce police occupational risks, improve knowledge of drug laws, and facilitate harm reduction strategies that promote human rights and community health.

The Spatial-Temporal Pattern of Policing Following a Drug Policy Reform: Triangulating Self-Reported Arrests With Official Crime Statistics.

BACKGROUND: In 2009, Mexico enacted a drug policy reform (Narcomenudeo) designed to divert persons possessing small amounts of illicit drugs to treatment rather than incarceration. To assess reform impact, this study examines the spatial-temporal trends of drug-related policing in Tijuana, Mexico post-enactment. METHOD: Location of self-reported arrests (N = 1,160) among a prospective, community-recruited cohort of people who inject drugs (PWID) in Tijuana (N = 552) was mapped across city neighborhoods. Official police reports detailing drug-related arrests was triangulated with PWID self-reported arrests. Exploratory spatial data analysis examined the distribution of arrests and spatial association between both datasets across three successive years, 2011-2013. RESULTS: In 2011, over half of PWID reported being detained but not officially charged with a criminal offense; in 2013, 90% of arrests led to criminal charges. Official drug-related arrests increased by 67.8% (p <.01) from 2011 to 2013 despite overall arrest rates remaining stable throughout Tijuana. For each successive year, we identified a high degree of spatial association between the location of self-reported and official arrests (p <.05). CONCLUSION: Two independent data sources suggest that intensity of drug law enforcement had risen in Tijuana despite the promulgation of a public health-oriented drug policy reform. The highest concentrations of arrests were in areas traditionally characterized by higher rates of drug crime. High correlation between self-reported and official arrest data underscores opportunities for future research on the role of policing as a structural determinant of public health.

Utilization of Google enterprise tools to georeference survey data among hard-to-reach groups: strategic application in international settings.

BACKGROUND: As geospatial data have become increasingly integral to health and human rights research, their collection using formal address designations or paper maps has been complicated by numerous factors, including poor cartographic literacy, nomenclature imprecision, and human error. As part of a longitudinal study of people who inject drugs in Tijuana, Mexico, respondents were prompted to georeference specific experiences. RESULTS: At baseline, only about one third of the 737 participants were native to Tijuana, underscoring prevalence of migration/deportation experience. Areas frequented typically represented locations with no street address (e.g. informal encampments). Through web-based cartographic technology and participatory mapping, this study was able to overcome the use of vernacular names and difficulties mapping liminal spaces in generating georeferenced data points that were subsequently analyzed in other research. CONCLUSION: Integrating low-threshold virtual navigation as part of data collection can enhance investigations of mobile populations, informal settlements, and other locations in research into structural production of health at low- or no cost. However, further research into user experience is warranted.

Examining the spatial distribution of law enforcement encounters among people who inject drugs after implementation of Mexico's drug policy reform.

In 2009, Mexico decriminalized the possession of small amounts of illicit drugs for personal use in order to refocus law enforcement resources on drug dealers and traffickers. This study examines the spatial distribution of law enforcement encounters reported by people who inject drugs (PWID) in Tijuana, Mexico to identify concentrated areas of policing activity after implementation of the new drug policy. Mapping the physical location of law enforcement encounters provided by PWID (n = 461) recruited through targeted sampling, we identified hotspots of extra-judicial encounters (e.g., physical/sexual abuse, syringe confiscation, and money extortion by law enforcement) and routine authorized encounters (e.g., being arrested or stopped but not arrested) using point density maps and the Getis-Ord Gi* statistic calculated at the neighborhood-level. Approximately half of the participants encountered law enforcement more than once in a calendar year and nearly one third of these encounters did not result in arrest but involved harassment or abuse by law enforcement. Statistically significant hotspots of law enforcement encounters were identified in a limited number of neighborhoods located in areas with known drug markets. At the local-level, law enforcement activities continue to target drug users despite a national drug policy that emphasizes drug treatment diversion rather than punitive enforcement. There is a need for law enforcement training and improved monitoring of policing tactics to better align policing with public health goals.

Mexico's "ley de narcomenudeo" drug policy reform and the international drug control regime.

It has been over half a century since the landmark Single Convention on Narcotic Drugs was adopted, for the first time unifying international drug policy under a single treaty aimed at limiting use, manufacture, trade, possession, and trafficking of opiates, cannabis, and other narcotics. Since then, other international drug policy measures have been adopted, largely emphasizing enforcement-based approaches to reducing drug supply and use. Recently, in response to concerns that the historic focus on criminalization and enforcement has had limited effectiveness, international drug policies have begun to undergo a paradigm shift as countries seek to enact their own reforms to partially depenalize or deregulate personal drug use and possession. This includes Mexico, which in 2009 enacted national drug policy reform partially decriminalizing possession of small quantities of narcotics for personal consumption while also requiring drug treatment for repeat offenders. As countries move forward with their own reform models, critical assessment of their legal compatibility and effectiveness is necessary. In this commentary we conduct a critical assessment of the compatibility of Mexico's reform policy to the international drug policy regime and describe its role in the current evolving drug policy environment. We argue that Mexico's reform is consistent with flexibilities allowed under international drug treaty instruments and related commentaries. We also advocate that drug policy reforms and future governance efforts should be based on empirical evidence, emphasize harm reduction practices, and integrate evidence-based evaluation and implementation of drug reform measures.

Cost-effectiveness of a police education program on HIV and overdose among people who inject drugs in Tijuana, Mexico.

Background: Incarceration is associated with drug-related harms among people who inject drugs (PWID). We trained >1800 police officers in Tijuana, Mexico on occupational safety and HIV/HCV, harm reduction, and decriminalization reforms (Proyecto Escudo). We evaluated its effect on incarceration, population impact and cost-effectiveness on HIV and fatal overdose among PWID. Methods: We assessed self-reported recent incarceration in a longitudinal cohort of PWID before and after Escudo. Segmented regression was used to compare linear trends in log risk of incarceration among PWID pre-Escudo (2012-2015) and post-Escudo (2016-2018). We estimated population impact using a dynamic model of HIV transmission and fatal overdose among PWID, with incarceration associated with syringe sharing and fatal overdose. The model was calibrated to HIV and incarceration patterns in Tijuana. We compared a scenario with Escudo (observed incarceration declines for 2 years post-Escudo among PWID from the segmented regression) compared to a counterfactual of no Escudo (continuation of stable pre-Escudo trends), assessing cost-effectiveness from a societal perspective. Using a 2-year intervention effect and 50-year time horizon, we determined the incremental cost-effectiveness ratio (ICER, in 2022 USD per disability-adjusted life years [DALYs] averted). Findings: Compared to stable incarceration pre-Escudo, for every three-month interval in the post-Escudo period, recent incarceration among PWID declined by 21% (adjusted relative risk = 0.79, 95% CI: 0.68-0.91). Based on these declines, we estimated 1.7% [95% interval: 0.7%-3.5%] of new HIV cases and 12.2% [4.5%-26.6%] of fatal overdoses among PWID were averted in the 2 years post-Escudo, compared to a counterfactual without Escudo. Escudo was cost-effective (ICER USD 3746/DALY averted compared to a willingness-to-pay threshold of $4842-$13,557). Interpretation: Escudo is a cost-effective structural intervention that aligned policing practices and human-rights-based public health practices, which could serve as a model for other settings where policing constitutes structural HIV and overdose risk among PWID. Funding: National Institute on Drug Abuse, UC MEXUS CONACyT, and the San Diego Center for AIDS Research (SD CFAR).

Syringe confiscation as an HIV risk factor: the public health implications of arbitrary policing in Tijuana and Ciudad Juarez, Mexico.

Female sex workers who inject drugs (FSW-IDUs) face elevated risk for HIV/STIs and constitute a key population for public health prevention. Through direct and indirect pathways including human rights violations, policing practices like syringe confiscation can compound FSW-IDU health risk and facilitate the spread of disease. We studied correlates of experiencing syringe confiscation among FSW-IDUs in northern Mexico, where formal policy allows for syringes to be available over the counter without a prescription, but police practices are often at odds with the law. FSW-IDUs reporting recent syringe sharing and unprotected sex with clients in Tijuana and Ciudad Juarez were administered surveys and HIV/STI testing. Logistic regression was used to identify correlates of syringe confiscation. Among 624 respondent FSW-IDUs, prevalence of syringe confiscation in the last 6 months was 48%. The following factors were positively associated with syringe confiscation: testing positive for HIV (adjusted odds ratio [aOR] = 2.54, 95% confidence interval [CI] = 1.11-5.80), reporting sexual abuse by police (aOR = 12.76, 95% CI = 6.58-24.72), engaging in groin injection (aOR = 1.84, 95% CI = 1.15-2.93), injecting in public (aOR = 1.64; 95% CI = 1.14-2.36), and obtaining syringes from pharmacies (aOR = 1.54; 95% CI = 1.06-2.23). Higher education level was negatively associated with syringe confiscation (aOR = 0.92, 95% CI = 0.87-0.98) as was frequent injection with clients within the last month (aOR = 0.64, 95% CI = 0.44-0.94). This analysis adds to the body of evidence linking unauthorized law enforcement actions targeting high-risk groups with HIV and other adverse health outcomes. Using a public health lens to conceptualize abuse as a structural risk factor, we advocate for multi-prong prevention, systematic monitoring, and evidence-based intervention response to deleterious police practices.

Unlocking deflection: The role of supervisor support in police officer willingness to refer people who inject drugs to harm reduction services.

BACKGROUND: Research is needed that investigates the relationship between police behaviors, attitudes, and perceived supervisor support as an implementation strategy of improving drug policy reforms. METHODS: We hypothesized that officers with more positive attitudes and practices would be more likely to report the perceived support of their supervisors. Data includes a sample of 1227 police officers who completed Project ESCUDO, a police education training program in Tijuana, Mexico. A negative binomial distribution was used to estimate associations between police behaviors and attitudes and perceived supervisor support. RESULTS: Officers who reported perceived supervisor support accounted for 29.2% (n=470) of the sample. Officers who referred people to social services were more likely and officers who broke syringes were less likely to report perceived supervisor support compared to officers who did not engage in these practices. Officers who believed: MOUD reduced criminal activity, "referring people who use drugs to social services is part of my job", and "laws that treat addiction as a public health problem make my job easier", were more likely to report perceived supervisor support. Beliefs that drug addiction is a disease, laws that treat addiction as a public health problem make their job easier, and talking to other law enforcement officers about infectious diseases were not significantly associated with perceived supervisor support. CONCLUSIONS: Our research highlights the importance of incorporating police supervisors as key actors in assuring officers' practices reflect current drug law reforms as well as embrace patient-centered approaches to managing encounters people who use opioids and inject drugs.

Drug checking in the fentanyl era: Utilization and interest among people who inject drugs in San Diego, California.

BACKGROUND: In North America, overdose rates have steeply risen over the past five years, largely due to the ubiquity of illicitly manufactured fentanyls in the drug supply. Drug checking services (DCS) represent a promising harm reduction strategy and characterizing experiences of use and interest among people who inject drugs (PWID) is a priority. METHODS: Between February-October 2022, PWID participating in a cohort study in San Diego, CA and Tijuana, Mexico completed structured surveys including questions about DCS, socio-demographics and substance use behaviors. We used Poisson regression to assess factors associated with lifetime DCS use and characterized experiences with DCS and interest in free access to DCS. RESULTS: Of 426 PWID, 72% were male, 59% Latinx, 79% were experiencing homelessness and 56% ever experienced a nonfatal overdose. One third had heard of DCS, of whom 57% had ever used them. Among the latter, most (98%) reported using fentanyl test strips (FTS) the last time they used DCS; 66% did so less than once per month. In the last six months, respondents used FTS to check methamphetamine (48%), heroin (30%) or fentanyl (29%). Relative to White/non-Latinx PWID, those who were non-White/Latinx were significantly less likely to have used DCS [adjusted risk ratio (aRR): 0.22; 95% CI: 0.10, 0.47), as were PWID experiencing homelessness (aRR:0.45; 95% CI: 0.28, 0.72). However, a significant interaction indicated that non-White/Latinx syringe service program (SSP) clients were more likely to have used DCS than non-SSP clients (aRR: 2.79; CI: 1.09, 7.2). Among all PWID, 44% expressed interest in free access to FTS, while 84% (of 196 PWID) expressed interest in advanced spectrometry DCS to identify and quantify multiple substances. CONCLUSIONS: Our findings highlight low rates of DCS awareness and utilization, inequities by race/ethnicity and housing situation, high interest in advanced spectrometry DCS versus FTS, and the potential role of SSPs in improving access to DCS, especially among racial/ethnic minorities.

Behavior change after fentanyl testing at a safe consumption space for women in Northern Mexico: A pilot study.

BACKGROUND: Fentanyl has led to an increased number of overdose deaths in North America. Testing substances for fentanyl may be a harm reduction strategy to prevent overdose. Little is known about behavior change after fentanyl testing and the attitudes around fentanyl knowledge and testing along the US-Mexico border in the context of a safe consumption site. METHODS: This was a pilot quantitative and qualitative study with 30 women who use drugs at an unsanctioned safe consumption site in Mexicali, Mexico. Women participated in a quantitative survey, a semi-structured interview, and fentanyl testing of substances. Injection behavior was observed after fentanyl testing results were provided. Qualitative data were collected to explore the meanings participants attributed to fentanyl and fentanyl testing. RESULTS: Half of the substances tested positive for fentanyl (n=15, 50%), and all of them were in samples of black tar heroin. Among those participants who tested positive for fentanyl, 7 (47%) subsequently used less of the intended substance, 1 did not use the intended substance, and 7 (47%) did not change their behavior (i.e., used as originally intended). In qualitative interviews, a predominant theme was a description of fentanyl as dangerous and deadly and fentanyl testing as being helpful for modifying drug use behaviors. However, participants recognized that there could be no change in behavior following a positive fentanyl test in the context of not being able to find substances free of fentanyl. CONCLUSION: We observed mixed results related to behavior change after women's intended substance for use tested positive for fentanyl. Fentanyl testing was acceptable to women, but behavior change was hampered by the inability to find substances free of fentanyl. Further research is needed to maximize the potential of fentanyl testing as a harm reduction tool especially in the context of a changing drug supply.