• Medetomidine, an animal sedative, is increasingly found in the US illegal drug supply, often mixed with fentanyl.
• Philadelphia saw a surge in medetomidine presence, with 72% of tested illegal opioid samples containing it by late 2024, surpassing xylazine.
• Severe withdrawal symptoms associated with medetomidine are resistant to standard opioid and xylazine withdrawal treatments, requiring intensive care and alternative medications like dexmedetomidine.

Medetomidine, an animal sedative, is increasingly being detected in the illegal drug supply across the United States, particularly in combination with fentanyl. This trend, highlighted in recent reports from the Centers for Disease Control and Prevention (CDC) and investigations by local health departments, is causing significant concern due to the severe withdrawal symptoms it induces, which are often resistant to traditional treatments for opioid and xylazine withdrawal. The rise of medetomidine is complicating the existing opioid crisis and posing new challenges for healthcare providers in managing overdose and withdrawal cases.

• What: Medetomidine, an animal sedative, is increasingly being mixed with illicit drugs, primarily fentanyl, leading to severe withdrawal symptoms and overdose complications.
• Who: Patients with opioid use disorder, healthcare providers, public health agencies, and drug users are all significantly affected.
• When: The rise of medetomidine was particularly noticeable in the last four months of 2024. Clusters of cases were reported between September 2024 and March 2025.
• Where: Significant clusters of medetomidine-related cases have been reported in Philadelphia, Chicago, and Pittsburgh. Testing for medetomidine was available at health system A in Philadelphia.

The emergence of medetomidine as a prevalent adulterant in the illegal drug supply represents a significant escalation in the challenges posed by the opioid crisis. Its presence complicates overdose reversal efforts, as naloxone may be less effective, and induces severe withdrawal symptoms that are resistant to traditional treatments. The need for ICU-level care for medetomidine withdrawal further strains healthcare resources. The rapid shift from xylazine to medetomidine highlights the dynamic nature of the drug supply and the need for continuous monitoring and adaptation of treatment strategies. The success of dexmedetomidine in managing withdrawal symptoms offers a potential therapeutic avenue, but its use requires careful monitoring and management, given its own potential for inducing withdrawal.

We knew what was in the drug supply, and we knew there was an abnormal syndrome in people, but it was hard to tie those together. Ultimately, it was a process of elimination.

The increasing prevalence of medetomidine in the illegal drug supply represents a significant and evolving threat to public health, demanding a multi-faceted and urgent response from healthcare providers and public health agencies. The co-occurrence of medetomidine with fentanyl, heroin, and other illicit substances intensifies the risk of severe adverse outcomes, including prolonged sedation, respiratory depression, bradycardia, hypotension, coma, and potentially fatal overdose. Medetomidine's effects are not reversed by naloxone, complicating overdose response and necessitating comprehensive supportive care, including airway management and cardiopulmonary support. The withdrawal syndrome associated with medetomidine is characterized by severe autonomic hyperactivity, often requiring intensive care and specialized treatment protocols. Effective strategies to mitigate the impact of medetomidine require improved detection methods, the development of targeted treatment protocols, continuous monitoring of the drug supply, and robust public awareness campaigns. Rapid drug testing methods are crucial for timely identification and intervention. Treatment protocols should address both opioid withdrawal and the unique challenges posed by medetomidine, potentially including the use of clonidine or dexmedetomidine to manage withdrawal symptoms. Public health initiatives should focus on educating individuals who use drugs, healthcare professionals, and first responders about the risks associated with medetomidine and strategies for harm reduction. These strategies could include wider distribution of naloxone, even though it doesn't directly counter medetomidine, as medetomidine is often found in combination with opioids. Furthermore, long-term strategies should include enhanced substance abuse prevention programs, expanded access to addiction treatment services, and addressing the underlying social determinants of drug use. Collaboration between public health agencies, law enforcement, and healthcare providers is essential to effectively monitor and respond to this emerging threat. Continuous research is needed to better understand the long-term effects of medetomidine use and to develop targeted interventions to improve outcomes for individuals struggling with opioid use disorder.