The General Hospital Corporation, doing business as Massachusetts General Hospital (MGH), has been awarded a $230,521 Project Grant from the National Institutes of Health (NIH) Trans-NIH Research Support program (CFDA 93.310) to study the effects of the synthetic opioid fentanyl and the veterinary sedative xylazine on respiratory function, metabolism, and wound healing in rats. The 2-year research project, which runs from July 1, 2024 to June 30, 2026, aims to provide a better understanding of the combined toxicity of these drugs in order to guide strategies for preventing and medically managing overdose victims. The study will quantify how fentanyl impacts xylazine-induced respiratory depression, hypotension, and bradycardia, as well as measure the effects of xylazine on skeletal muscle, thermoregulation, and wound healing, both alone and in combination with fentanyl.