RÉSUMÉ
Mitragynine is the primary active alkaloid in the leaves of the tropical tree Mitragyna speciosa, and goes by the popular names "Kratom", biak-biak and maeng da. Mitragynine is increasingly seen in forensic toxicology casework including driving under the influence of drugs and medicolegal death investigation cases. The toxicity of mitragynine continues to be debated in the scientific community as advocates highlight its long history of use in Southeast Asia and testimonials to its benefits by present-day users, while opponents point to an increasing number of adverse events tied to mitragynine use in Western societies. Quantitative reports of mitragynine in biological specimens from forensic investigations in the literature are sparse and may be influenced by poor analyte stability and inadequate resolution of mitragynine from its diastereomers, which could lead to falsely elevated concentrations and subsequently render those reported concentrations inappropriate for comparison to a reference range. Over the course of 27 months, 1,001 blood specimens submitted to our laboratory tested positive for mitragynine using a sensitive and specific quantitative LC-MS/MS method; concentrations ranged from 5.6-29,000 ng/mL, with mean and median concentrations of 410 ± 1,124 and 130 ng/mL, respectively. Mitragynine presents an analytical challenge that requires a method that appropriately separates and identifies mitragynine itself from its isomers and other related natural products. We describe a validated analytical method and present a short series of case reports that provide examples of apparent adverse events, and the associated range of mitragynine concentrations. This type of analytical specificity is required to appropriately interpret mitragynine concentrations detected in biological specimens from forensic casework and assess its potential toxicity.
