Chelsea L. Shover
Chelsea L. Shover, PhD is an Assistant Professor at the David Geffen School of Medicine at UCLA, where she directs the Epidemiology, Policy, and Implementation Lab (EPI Lab). The EPI Lab’s work unites quantitative data analysis with community based participatory research on overdose, substance use disorders, infectious diseases, and homelessness. Dr. Shover completed her PhD in epidemiology at the UCLA Fielding School of Public Health, followed by a postdoctoral fellowship in Psychiatry and Behavioral Sciences at Stanford University School of Medicine. Dr. Shover’s team has identified key U.S. drug supply changes (i.e., fentanyl’s westward spread, emergence of xylazine, rapid introduction of industrial chemical BTMPS into the illicit fentanyl supply) and then worked with policymakers and community organizations to improve on-the-ground overdose prevention. She was awarded a K01 career development award in 2021, and an R01 from the National Institute of Health’s Helping End Addiction Long-Term Initiative in 2022. Dr. Shover’s work is currently funded by the National Institute on Drug Abuse and Centers for Disease Control and Prevention to improve overdose surveillance in Los Angeles and operate a drug checking program at syringe services programs. She is an Associate Editor for Addiction. Alongside her academic research, Dr. Shover has worked in local government, community clinics, and policy advising capacities, all of which inform her team’s approach to urgent and complex public health problems. In 2021, she collaborated with local and state public health partners to arrange LA50K, a pilot program of 50,000 naloxone kits to distribute to people experiencing homelessness in Los Angeles. As a member of the Stanford-Lancet Commission on the North American Overdose Crisis, she co-authored a report published in the Lancet in 2022 and has given international briefings on the report’s recommendations. In 2023, she was invited to join a working group of the United Kingdom’s Advisory Council on the Misuse of Drugs to contribute to a report making recommendations to prevent public health harms associated with xylazine. She has continued to engage with the Home Office about emerging substances. As an educator, Dr. Shover is especially committed to mentoring trainees from underrepresented in science, including people with personal experience of substance use disorders and mental illness.
Session
Background: Quantitative information is rarely available about illicit drugs at all, much less at the consumer level.
Objectives: To determine the mean, median, and range of purity of illicit drugs – specifically, fentanyl, methamphetamine, heroin, and cocaine – along with adulterants and co-detected compounds.
Methods: Samples were submitted anonymously for testing at community-based sites throughout Los Angeles. Quantitative testing was performed using liquid chromatography mass spectrometry. Quantified compounds included: fentanyl, fluorofentanyl, two fentanyl synthesis chemicals (4-ANPP, phenylethyl 4-ANPP), heroin, cocaine, methamphetamine, and xylazine. Results were reported in percent mass, with 0.1% imputed as the limit of quantitation. A voluntary survey was used to determine expected contents and other drug-level characteristics.
Results: Between September 2023 and November 2024, 333 samples bought as fentanyl (n=199), methamphetamine (n=67), heroin (n=42), or cocaine (n=25) were tested. Mean purity varied substantially by drug (Figure 1). Samples bought as fentanyl had mean purity of 9% (SD: 11%), median 5%, range: 0.1%, 48%, with a high variability of co-detected compounds including fluorofentanyl, xylazine, UV stabilizer Bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (BTMPS), and stimulants. Of heroin samples, 15 (36%) contained fentanyl with an average concentration of 2%. In contrast, methamphetamine (mean purity: 57%, SD: 21%, median: 59%, range: 0.1%, 95%) and cocaine (mean purity: 56%, SD: 19%, median: 63%, range: 24%, 81%) samples contained only these compounds.
Implications: Tremendous variability in purity at the street level – often from samples procured within extremely close geographic and temporal proximity – highlights possible scenarios for overdose risk, as well as implications for how pre-treatment exposure may support higher starting doses of opioid agonist treatment.