Testing for protonitazene in human hair using LC–MS-MS.

This article focuses on the development and validation of a liquid chromatography-tandem mass spectrometry (LC–MS-MS) method for detecting protonitazene, a synthetic benzimidazole opioid from the nitazenes class, in human hair. Protonitazene, originally synthesized in the 1950s as a potent analgesic but never marketed due to severe side effects and dependence risk, has recently emerged as a new psychoactive substance with increasing public health concerns. The validated method demonstrated high sensitivity and selectivity, with a detection limit of 0.1 pg/mg, and was successfully applied to hair samples from two deceased individuals and two living co-prisoners in a French overseas department, confirming protonitazene exposure. This study represents the first reported identification of protonitazene in human hair, highlighting hair analysis as a valuable tool for monitoring long-term use of novel synthetic opioids in forensic and clinical toxicology contexts.