Clinical toxicity of nitazene detections in two Australian emergency department toxicosurveillance systems

Introduction: Nitazenes are a group of potent synthetic opioids that have had increasing prominence as novel psychoactive drugs in the last 5 years. We describe emergency department nitazene-related presentations. Methods: This is a prospective series of patients with analytically confirmed nitazene presentations identified by the Emerging Drugs Network of Australia and Emerging Drugs Network of Australia Victoria. Both studies' databases were searched between July 2020 and February 2024 with clinical data and blood nitazene concentrations abstracted. Results: There were 32 presentations, 23 (72%) males, with a median age of 31 years (range 18–63 years). Only five (16%) intentionally ingested a nitazene, with most (12, 38%) believing they had taken alternative opioids. Co-exposures occurred in 31 (97%), mostly metamfetamine. Naloxone was administered in 23 (72%) presentations, with a median total dose of intravenous naloxone within 1 h post hospital presentation of 400 μg (interquartile range [IQR] 160–450 μg). Four (13%) received a naloxone infusion. Thirteen (41%) were admitted to the intensive care unit. The median length of stay was 17 h (IQR 7–39 h). Protonitazene was the commonest nitazene detected in 23 (72%) presentations with a median concentration of 2.0 μg/L (range 0.7–15 μg/L). The lowest concentration of protonitazene in a patient that received naloxone was 0.7 μg/L. Discussion and Conclusions: Most patients were unaware they were using nitazenes. Given their potency, this has important implications for harm, particularly in those not intentionally using opioids. Nitazene exposure was mostly unintentional. Naloxone use was common and standard dosing regimens appeared effective in most cases.