Pharmacokinetics of N,N-dimethyltryptamine in Humans.

DMT, a psychedelic compound being developed for major depressive disorder, is rapidly cleared from the body with a mean elimination half-life of 9 to 12 minutes. In vitro experiments showed that blocking monoamine oxidase A and certain cytochrome P450 enzymes (CYP2D6 and, to a lesser extent, CYP2C19) slowed DMT's clearance. The drug has low lipophilicity and low plasma protein binding, meaning a high proportion is available for distribution and metabolism, consistent with its very fast clinical pharmacokinetics. In a phase I trial, 24 healthy adults received single escalating intravenous infusions of DMT (9–21.5 mg freebase) over 10 minutes. All doses were safe and well tolerated, and peak plasma concentrations did not relate to body weight or BMI. These results support developing novel DMT infusion regimens for treating major depressive disorder.

Study at a glance

Abstract

N,N-dimethyltryptamine (DMT) is a psychedelic compound under development for the treatment of major depressive disorder (MDD). This study evaluated the preclinical and clinical pharmacokinetics and metabolism of DMT in healthy subjects. The physiochemical properties of DMT were determined using a series of in vitro experiments and its metabolic profile was assessed using monoamine oxidase (MAO) and cytochrome P450 (CYP) inhibitors in hepatocyte and mitochondrial fractions. Clinical pharmacokinetics results are from the phase I component of a phase I/IIa randomised, double-blind, placebo-controlled, parallel-group, dose-escalation trial (NCT04673383). Healthy adults received single escalating doses of DMT fumarate (SPL026) via a two-phase intravenous (IV) infusion. Dosing regimens were calculated based on pharmacokinetic modelling and predictions with progression to each subsequent dose level contingent upon safety and tolerability. In vitro clearance of DMT was reduced through the inhibition of MAO-A, CYP2D6 and to a lesser extent CYP2C19. Determination of lipophilicity and plasma protein binding was low, indicating that a high proportion of DMT is available for distribution and metabolism, consistent with the very rapid clinical pharmacokinetics. Twenty-four healthy subjects received escalating doses of DMT administered as a 10-min infusion over the dose range of 9-21.5 mg (DMT freebase). DMT was rapidly cleared for all doses: mean elimination half-life was 9-12 min. All doses were safe and well tolerated and there was no relationship between peak DMT plasma concentrations and body mass index (BMI) or weight. This is the first study to determine, in detail, the full pharmacokinetics profile of DMT following a slow IV infusion in humans, confirming rapid attainment of peak plasma concentrations followed by rapid clearance. These findings provide evidence which supports the development of novel DMT infusion regimens for the treatment of MDD. Registered on ClinicalTrials.gov (NCT04673383).