Letter to the Editor.

Abstract

We have read with great interest the report by Wiltshire et al.,1 which suggests a possible link between the death of a healthy young man in southwest England in 2008 and the South American botanical hallucinogen ayahuasca. This study is important as it highlights the complex link between life-threatening reactions and the ingestion of ayahuasca.2 However, the study has several important limitations, and it does not offer sufficient information to support the possible causal role of ayahuasca or its alkaloids in the death of the young man. For instance, Wiltshire et al. affirm that the leaves of Psychotria viridis “...contain harmine and other beta-carboline alkaloids, but also, significantly, the alkaloid dimethyltryptamine (DMT)” (pg. 74). However, the main alkaloid present in P. viridis is DMT, and this plant lacks harmine.3 The authors also suggest that the monoamine oxidase inhibition produced by the beta-carbolines in ayahuasca could increase the levels of endogenous DMT, producing psychoactive effects (pg. 74), and that alcohol may “...facilitate the passage of DMT into the blood and, given thewidespread consumption of alcohol, this is an important consideration.” (pg. 75). This assertion is merely theoretical, as we are not aware of any study in humans that report the link between ayahuasca administration and increased levels of endogenous DMT, and the clinical use of monoamine oxidase inhibitors is not associated with psychedelic effects.4 We are also not aware of human studies demonstrating that alcohol increases DMT levels in the blood. Furthermore, the warning against the combined consumption of alcohol and ayahuasca seems exaggerated, as ayahuasca is not widely used5 and alcohol is usually avoided in ayahuasca rituals.6 The evidence used byWiltshire et al. to suggest the causal role of ayahuasca or its alkaloids, especially DMT, is very limited. For instance, it seems that the man's ileum and colon were examined microscopically, revealing spores of Psilocybe mushrooms, pollen of Cannabis, and seeds of opium poppy, but chemical analysis was performed only in the stomach and exclusively for DMT. Importantly, the authors do not report any quantitative analysis of DMT. Therefore, it is not possible to know whether the young man ingested other recreational drugs (such as opiates, psychostimulants, or other hallucinogens) or therapeutic medications (for example, for treating psychiatric, neurological, hepatic, or cardiovascular disorders). Thus, it is possible that some other drug or drug combination could have contributed to his death. For instance, the combination of the monoamine oxidase inhibitors present in ayahuasca with substances such as selective serotonin reuptake