Illicitly-manufactured fentanyls (fentanyl) have changed the risk environment of people who use drugs (PWUD). In California and many western US states, the opioid overdose rate spiked from 2016 to 2021, driven largely by fentanyl. Mexican border cities act as transit through-points for the illicit drug supply and similar evolving health risks are likely to be present. Nevertheless, due to data gaps in surveillance infrastructure, little is known about fentanyl prevalence in Mexico.
We employ intensive ethnographic participant-observation among PWUD, as well as key informants including harm reduction professionals, EMTs, and physicians on the front lines in Tijuana, Mexico. We triangulate interview data and direct observations of consumption practices with n=652 immunoassay-based fentanyl tests of drug paraphernalia from mobile harm reduction clinics in various points throughout the city.
PWUD informants described a sharp increase in the psychoactive potency and availability of powder heroin-referred to as “china white”-and concomitant increases in frequency of overdose, soft tissue infection, and polysubstance methamphetamine use. Fentanyl positivity was found among 52.8% (95%CI: 48.9-56.6%) of syringes collected at harm reduction spaces, and varied strongly across sites, from 2.7% (0.0-5.7%) to 76.5% (68.2-84.7%), implying strong market heterogeneity. Controlling for location of collection, syringe-based fentanyl positivity increased by 21.7% (10.1-42.3%) during eight months of testing. Key informants confirm numerous increased public health risks from fentanyl and describe the absence of a systematic or evidence-based governmental response; naloxone remains difficult to access and recent austerity measures have cut funding for harm reduction in Mexico.
Fentanyl, linked to powder heroin, is changing the risk environment of PWUD on the US-Mexico border. Improved surveillance is needed to track the evolving street drug supply in Mexico and related health impacts for vulnerable populations. Structural factors limiting access to naloxone, harm reduction, substance use treatment, and healthcare, and minimal overdose surveillance, must be improved to provide an effective systemic response.

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