Acute toxic leucoencephalopathy following protonitazene ingestion.

Authors

Ruadhan O'Laoi, Holly Acton, Pierce Kavanagh, Isabelle Hunt, Niall Sheehy, Cormac Kennedy

Published in

British journal of clinical pharmacology. Sep 06, 2026. Epub Sep 06, 2026.

Abstract

Distribution of illicit counterfeit alprazolam containing the highly potent synthetic opioid-receptor agonist protonitazene recently resulted in a number of severe overdoses in Ireland. We report three cases that presented to our hospital, within 6 weeks of one another, following ingestion of illicitly-sourced alprazolam. All cases demonstrated clinical and radiological findings consistent with acute toxic leucoencephalopathy.
A 19-year-old male ingested several tablets of counterfeit alprazolam. Magnetic resonance imaging (MRI) demonstrated mild white matter changes consistent with acute toxic leucoencephalopathy. He was extubated after 6 days and made a full neurological recovery by Day 22. A 30-year-old male suffered an out-of-hospital cardiac arrest following ingestion of illicitly sourced alprazolam. MRI demonstrated extensive white matter changes in a distribution consistent with severe acute toxic leucoencephalopathy. There was no neurological recovery, and he passed away 30 days following presentation. A 36-year-old male was found surrounded by empty packaging of illicitly-sourced alprazolam. He was intubated and subsequent MRI demonstrated near-identical features to that of Case 2. He made no neurological recovery by Day 27 and passed away on Day 45. Analysis by gas chromatography-mass spectrometry identified protonitazene in the recovered tablets of Cases 1 and 2. Case 3 had no tablets available for analysis, though the empty alprazolam packaging was identical to that seen in Cases 1 and 2.
These cases describe a trio of local protonitazene poisonings that were associated with the development of acute toxic leucoencephalopathy. Prognosis was poor but variable, with a correlation between radiological severity and neuroprognostication.

PMID:
42702575
Bibliographic data and abstract were imported from PubMed on 07 Sep 2026.

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