Date of Award

January 2022

Document Type


Degree Name

Master of Public Health (MPH)


School of Public Health

First Advisor

Robert Heimer

Second Advisor

Lauretta E. Grau


Background: Xylazine, a sedative analgesic drug approved as an animal tranquilizer but not for human use, has become an adulterant in the supply of heroin/fentanyl.(Greene & Thurmon, 1988) Between 2019 and 2020, prevalence of xylazine in overdose death reports increased by 44.8% nationally.(Friedman et al., 2021) The three jurisdictions in 2020 with the highest prevalence of xylazine were Philadelphia (25.8%), Maryland (19.3%), and Connecticut (10.2%).(Friedman et al., 2021) Not much is known about how xylazine’s impacts on service provider’s practices and the people they serve.

Objectives: Use a multiple methods approach to understand xylazine’s presence and impact in Connecticut, and document challenges and solutions from Connecticut and Philadelphia.

Data Collection and Analysis: Service providers in Connecticut (n=7; thematic saturation) and in Philadelphia (n=3; entire team) were interviewed about their response practices and understanding/ observations of xylazine in the population they serve. Results were coded and analyzed using a rapid thematic assessment. (Watkins, 2017) Conditional logistic regression was run on overdose death data from the office of the chief medical examiner in Connecticut, to understand the relationship between the presence of xylazine and predictors such as urban/rural status and the presence of other drugs or alcohol. Logistic regression was also constructed on a fentanyl/xylazine survey of people who use drugs in Connecticut (n=453), asking about 1) use of fentanyl test strips, 2) awareness of xylazine, 3) potential use of a xylazine test strip, and 4) concerns about the unpredictable drug supply.

Main Results: Qualitative analysis showed that 1) xylazine has had a noticeable impact on the people providers serve, both in Connecticut and Philadelphia, 2) there are a range of implemented and unimplemented practices to better prevent and respond to xylazine harms, including oxygen therapy and 3) there are misconceptions by bystanders on how to respond to overdose, specifically a misunderstanding of when and how much naloxone to administer, and not knowing to use rescue breathing in between doses of naloxone.

Conditional logistic regression showed the presence of fentanyl or fentanyl analogues was a statistically significant predictor of xylazine presence. (OR=3.54, 95%CI (2.0-9,6.55)) This is consistent with existing research showing an “ecological” relationship between xylazine and fentanyl. (Friedman et al., 2021) Additionally, analysis showed overdose death occurrences in larger cities (80,000+) were less likely to include xylazine. (OR=0.63, 95%CI (0.46,0.84))

Analysis of fentanyl/xylazine survey data showed that of the total 453 respondents, 317 reported they did not use fentanyl test strips, 70 were unaware of the presence of xylazine, 158 after being informed about xylazine said they may use a xylazine test strip if they were available, and 331 respondents were sometimes concerned about the unpredictable drug supply. Respondents who injected drugs were more likely to say they would use a xylazine test strip. (OR=4.1345)

Discussion and Public Health Implications: This work shows the need for 1) expanded harm reduction education with fidelity to best practices and 2) drug testing, including xylazine test strip development, and a safer drug supply. This study reveals that the opioid crisis and the changing illicit drug market have health impacts on people who use drugs beyond overdose deaths, that are not fully understood and are largely unmet.


This thesis is restricted to Yale network users only. It will be made publicly available on 11/19/2022