Metabolism and disposition of N,N-dimethyltryptamine and harmala alkaloids after oral administration of ayahuasca

This double-blind crossover, balanced design study (n=10) investigated the metabolism and excretion of harmala alkaloids after oral administration of ayahuasca (75mg DMT), by analyzing the metabolic content of urine samples across time.

Abstract

“Introduction: Ayahuasca is an Amazonian psychotropic plant tea obtained from Banisteriopsis caapi, which contains β‐carboline alkaloids, chiefly harmine, harmaline and tetrahydroharmine. The tea usually incorporates the leaves of Psychotria viridis or Diplopterys cabrerana, which are rich in N,N‐dimethyltryptamine (DMT), a psychedelic 5‐HT_2A/1A/2C agonist. The β‐carbolines reversibly inhibit monoamine‐oxidase (MAO), effectively preventing oxidative deamination of the orally labile DMT and allowing its absorption and access to the central nervous system. Despite increased use of the tea worldwide, the metabolism and excretion of DMT and the β‐carbolines has not been studied systematically in humans following ingestion of ayahuasca.

Methods: In the present work, we used an analytical method involving high performance liquid chromatography (HPLC)/electrospray ionization (ESI)/selected reaction monitoring (SRM)/tandem mass spectrometry(MS/MS) to characterize the metabolism and disposition of ayahuasca alkaloids in humans. Twenty‐four‐hour urine samples were obtained from 10 healthy male volunteers following administration of an oral dose of encapsulated freeze‐dried ayahuasca (1.0 mg DMT/kg body weight).

Results: showed that less than 1% of the administered DMT dose was excreted unchanged. Around 50% was recovered as indole‐3‐acetic acid but also as DMT‐N‐oxide (10%) and other MAO‐independent compounds. Recovery of DMT plus metabolites reached 68%. Harmol, harmalol, and tetrahydroharmol conjugates were abundant in urine. However, recoveries of each harmala alkaloid plus its O‐demethylated metabolite varied greatly between 9 and 65%.

Discussion: The present results show the existence in humans of alternative metabolic routes for DMT other than biotransformation by MAO. Also that O‐demethylation plus conjugation is an important but probably not the only metabolic route for the harmala alkaloids in humans.“

Authors: Jordi Riba, Ethan H. McIlhenny, Marta Valle, José Carlos Bousoa & Steven A. Barker

Summary

Introduction

Ayahuasca is a psychotropic plant tea obtained from the stems of the jungle liana Banisteriopsis caapi. It is used in religious ceremonies and shamanic medicine by many Amazonian peoples, but has attracted new uses and has raised public health concerns.

Ayahuasca’s psychotropic effects arise from the pharmacological interaction between the b-carboline alkaloids present in B. caapi and the tryptamines found in P. viridis and D. cabrerana. The b-carbolines block the enzyme monoamine-oxidase A (MAO-A), rendering the DMT present in the plants orally active.

Early studies had already observed that DMT lacked psychoactive effects after oral administration. However, following parenteral administration, DMT disappeared from plasma very rapidly.

MAO may not be the sole metabolic pathway in humans for the breakdown of DMT, as N-oxidation, N-demethylation and cyclization have been described.

A preliminary assessment of the metabolism and urinary disposition of DMT and the harmala alkaloids following ayahuasca administration was conducted in a group of healthy volunteers.

Materials and methods

Volunteers

Ten young healthy male volunteers were recruited. They were experienced psychedelic drug users and underwent a structured psychiatric interview to exclude current or past history of Axis-I disorders and alcohol or other substance dependence.

Drugs

Ayahuasca was administered orally as an encapsulated lyophilizate containing 8.33mg DMT, 14.13mg harmine, 0.96 mg harmaline, and 11.36 mg tetrahydroharmine (THH) per gram.

Study design and sample collection

In a clinical trial involving three experimental sessions, urine samples were obtained from participants who received lactose placebo, 20 mg d-amphetamine, and 1.0mg DMT/kg body weight ayahuasca. The amounts of harmine, harmaline, and tetrahydroharmine recovered in urine are reported together with their potential O-demethylated metabolites. Each experimental session consisted of 24 h urine collection, which was subdivided into 4 time intervals. The collected urine was well mixed, and 50 ml aliquots were separated and stored at 80 C until analysis.

Analytical method

McIlhenny et al. used high performance liquid chromatography with electrospray ionization and tandem mass spectrometry to analyze urine samples.

The liquid chromatography-tandem mass spectrometry method was used to determine the following compounds: DMT, IAA, DMT-NO, NMT, 5-hydroxy-DMT, dimethylkynuramine, 2MTHBC, 5-methoxy-DMT, harmine, harmaline, tetrahydroharmine, harmol, harmalol, and tetrahydroharmol.

Statistics

Descriptive statistics were used to report the amounts of the different compounds measured, and percentage recoveries were calculated relative to the amount of parent compound administered.

Results and discussion

DMT and metabolite excretion was maximal during the first third of the 24 h collection period.

We performed additional calculations to address the relative contribution of oxidative deamination and of MAO-independent metabolism, mainly N-oxidation, to the biotransformation of DMT. The results show that IAA makes up roughly 80% of all substances found in urine.

THH was the most abundant alkaloid in urine followed by harmaline and harmine. Enzymatic treatment increased the amount of recovered harmine but decreased the amount of recovered harmaline and THH.

After enzymatic treatment, the amount of tetrahydroharmol, harmalol and harmol increased by a factor of 50, 3, 2 and 1.5, respectively. The amount of free harmol was 2%, while free harmalol was 36% and free tetrahydroharmol was 68%.

The vast majority of harmol and harmalol recovered in urine after ayahuasca ingestion must necessarily be formed through the metabolic breakdown of harmine and harmaline. Tetrahydroharmol was not present in the ayahuasca batch analyzed for alkaloid content.

The disposition of harmala alkaloids and their metabolites was more evenly distributed throughout the 24-h collection period than that of DMT and its breakdown products.

In the present study, ayahuasca alkaloids were found to undergo extensive metabolism in the urine of humans.

Early investigations in humans had found that DMT was not psychoactive when administered alone per os. A recent study found that DMT was measurable in blood at 30 min but almost undetectable at 1 h.

DMT is metabolized by MAO-catalyzed oxidative deamination in the brain, liver and kidney, and by N-demethylation in the urine. DMT-NO is a major metabolite, accounting for 20% of all tryptamine derivatives measured in urine and 10% of the administered DMT dose.

Studies of DMT metabolism in vitro have shown that other pathways besides oxidative deamination also contribute to DMT metabolism. These pathways include DMT-NO, NMT, N-oxidation, N-demethylation, MAO, and 2-MTHBC.

In the absence of mitochondrial MAO inhibition, DMT-NO appears to be the major metabolite of DMT, and the formation of DMT-NO is shifted toward lower levels in the absence of harmalas.

The b-carbolines, harmine and harmaline, appeared to undergo extensive metabolism with low urine recoveries. Large amounts of harmol and harmalol were found in urine, and these compounds were also found in plasma in a clinical study.

The recoveries of the harmala alkaloid plus its O-demethylation product were lower than expected, and the percentage recovery for THH + tetrahydroharmol was as little as 9%. This suggests that THH undergoes an intense first pass effect and does not reach systemic circulation.

Conclusion

Results show that N-oxidation is a major degradation pathway for DMT in humans, and that O-demethylation plus conjugation is an important but probably not the only degradation route for the harmala alkaloids in humans.

Acknowledgements

The authors thank the Cottonwood Research Foundation and THC Pharm for their support. Marta Valle was supported by the Spanish Health Ministry.