Toxicokinetics and analytical toxicology of four N, N-dimethyltryptamine derivatives studied in human in vitro systems and in vivo by means of zebrafish embryos.

N,N-Dimethyltryptamine (DMT) is a naturally occurring substituted tryptamine used as a psychedelic drug for ritual purposes by various cultures. Derivatives were already found on the drug of abuse market, such as N1-tert-butoxycarbonyl-N,N-dimethyltryptamine (DMT-Boc). The aim of the current study was to investigate the toxicokinetics of DMT-Boc and three related DMT derivatives, by name DMT-isopropylcarbamate, DMT-pivaloylamide, and DMT-THP (N,N-dimethyl-2-[1-(oxan-2-yl)indol-3-yl]ethanamine). In vitro and in vivo metabolism studies with pooled human liver S9 incubations and zebrafish embryos were performed, respectively. Monooxygenase and monoamine oxidase (MAO) isozymes involved in the phase I metabolism were identified. In vitro metabolic stability and plasma protein binding (PPB) were evaluated. A total of 11 metabolites for DMT-Boc, 13 for DMT-isopropylcarbamate, eight for DMT-pivaloylamide and 16 for DMT-THP were identified using high-resolution tandem mass spectrometry. N-Demethylation and hydroxylation were the most relevant metabolic reactions. CYP1A2, CYP2D6, and FMO3 were identified as most active phase I isozymes and MAO-A contributed to DMT-THP metabolism. The in vitro half-lives of DMT-Boc, DMT-isopropylcarbamate, and DMT-pivaloylamide were calculated to be between 74 and 79 min, while that of DMT-THP was found to be > 180 min. All compounds showed high PPB (> 99%) indicating that co-consumption with other drugs might increase the DMT derivatives' toxicity. Combined in vitro and in vivo approaches provided a comprehensive metabolism overview. N, N-bis-Demethylated, N-demethylated and N-oxygenated metabolites along with parent compound were proposed as consumption markers in order to support clinical and forensic toxicologists to identify these substances in biosamples in case of suspected abuse.