The emergence of veterinary sedatives such as xylazine and medetomidine as adulterants in the illicit drug supply poses increasing challenges to clinical toxicology and public health. Medetomidine, a potent alpha-2 adrenergic receptor agonist not approved for human use, has recently been detected in overdose cases, particularly in fentanyl-positive individuals. To address this, we developed and validated a liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay capable of detecting xylazine and medetomidine in urine with minimal sample preparation, a 60-min hydrolysis incubation, and a 7-min chromatographic run time. Analytical validation demonstrated acceptable precision, accuracy, linearity, and minimal matrix effects. We then analyzed 100 retrospective urine samples from a polydrug-using population. Xylazine was detected in 20 % and 3-hydroxymedetomidine (medetomidine's primary metabolite in urine) in 12 % of samples, with both compounds most frequently co-occurring with fentanyl. A subset of medetomidine-positive cases also tested positive for xylazine, indicating potential co-adulteration. This study highlights the value of expanded toxicological testing in identifying emerging adulterants that may otherwise go undetected by routine screening.
Keywords: LC-MS/MS and adulterant; Medetomidine; Xylazine.
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