# A Medical Examiner Chases Down an Elusive Killer
Dr. Darinka Mileusnic-Polchan, Knoxville's chief medical examiner, has become a detective on the front lines of an evolving overdose crisis. Synthetic opioids beyond fentanyl continue to appear in street drug supplies, killing users with little warning and outpacing toxicology labs' ability to identify them.
The problem: standard drug testing cannot always detect emerging synthetic opioids before they claim lives. Mileusnic-Polchan works to rapidly identify new compounds appearing in overdose deaths so public health officials can alert communities and clinicians about what's circulating. Her work matters because knowledge saves lives. When emergency departments know which opioid killed someone, they can adjust naloxone protocols and prepare treatment plans.
Recent years have seen xylazine, nitazenes, and isotonitazene surface in fatal overdoses across the country. These drugs either don't respond to naloxone or respond poorly, creating a treatment nightmare for paramedics and emergency physicians. Xylazine, a veterinary sedative, produces skin wounds and addiction similar to heroin but resists overdose reversal medications. Nitazenes are synthetic opioids banned in many countries that produce overdose deaths with minimal warning.
Mileusnic-Polchan and her team use advanced toxicology methods to identify compounds in deceased people's blood and tissues. Once identified, they communicate findings to harm reduction organizations, public health departments, and law enforcement. This intelligence allows harm reduction workers to counsel drug users about what's in local supplies and equip them with overdose prevention tools.
The lag between a death and identification creates a dangerous gap. An opioid killing people today might not be officially identified for weeks or months, leaving users un