DMT + harmine (pharmahuasca) increases glucose consumption in the brain

A new study by researchers from the University of Zurich and Bern University Hospital has, for the first time, mapped out what happens to the energy consumption of the brain takes place during a DMT experience, using an advanced PET scanning technique.
The study has been published in Journal of Cerebral Blood Flow & Metabolism and investigated the combination of DMT with harmine, also known as "pharmahuasca": a synthetic replica of the active ingredients in ayahuasca.

What is pharmahuasca?

DMT (N,N-dimethyltryptamine) normally has only a short-lived effect, as it is rapidly broken down by the enzyme MAO-A.
By combining DMT with harmine, an MAO-A inhibitor that also occurs naturally in ayahuasca, this breakdown is inhibited, resulting in a psychedelic experience that 4 to 5 hours lasts, similar to a traditional ayahuasca session but using purified, measured substances.
In this study, 14 healthy men were administered 90 mg of DMT combined with 120 mg of harmine, or a placebo, via the buccal mucosa (buccal route), in a single-blind crossover design.

How was it measured?

The researchers used [¹⁸F]FDG-PET scans to assess the cerebral metabolic rate for glucose utilisation (CMRglc) to measure: how much energy the brain actually consumes.
The scans were taken during the peak of the effect, between 100 and 170 minutes after administration, when the psychedelic effects are at their strongest.
Previous neuroimaging studies into DMT have mainly focused on functional connectivity (how different areas of the brain communicate with one another) and EEG signals, but the actual energy consumption of the brain during a DMT trip has, until now, remained largely unexplored territory.

Key findings

Total glucose consumption in the brain increased by 12,5% under the influence of DMT + harmine, compared with placebo (t = 2.58, p = 0.011), a statistically significant increase.
Analyses by brain region and by network showed that this increase widespread was observed across the cortex, with the strongest increases in what are known as higher-order brain networks – the networks involved in more complex cognitive processes such as self-reflection and the attribution of meaning.
Furthermore, exploratory analyses revealed a significant positive correlation between total glucose consumption and the amount of harmine in the blood, but not with the amount of DMT in the blood or with how intensely participants subjectively rated the experience.

How does this compare with psilocybin?

The researchers emphasise that this finding is a a classic effect of psilocybin reiterates: an increase in glucose metabolism in the brain has previously been observed with psilocybin as well.
The fact that DMT and harmine exhibit the same pattern suggests that this overall increase in energy consumption may be a shared metabolic characteristic refers to the psychedelic state in general, regardless of the specific substance used.

Conclusion

A psychedelic dose of DMT + harmine increases glucose metabolism in the brain on a widespread scale, particularly in brain networks involved in higher-order thought processes.
This reinforces the view that, despite their different chemical targets, psychedelics may act via a shared underlying mechanism at the level of brain energy and metabolism, which in turn provides avenues for future therapeutic research.

Addition

This study is particularly interesting because it is a physiological, measurable basis refers to something that people often describe subjectively following an ayahuasca or DMT experience: the sensation of intense mental activity, accelerated thought processes and a feeling of processing "more" than usual.
It is striking that the level of harmine in the blood was linked to glucose consumption, rather than the amount of DMT or how intensely a person subjectively experienced the trip.
This suggests that harmine, the compound in traditional ayahuasca that is often somewhat overshadowed by DMT, may play a greater role in the underlying brain processes than previously thought.
For those interested in the science behind ayahuasca and pharmahuasca experiences, this research reaffirms that reproducible, measurable changes occur in the brain, further establishing it as a serious field of research within psychedelic science.

Source: Egger K, Bozsak R, Aicher HD, et al. "Global increases in brain glucose metabolism following acute administration of N,N-dimethyltryptamine and harmine in healthy volunteers: A randomised [18F]FDG-PET study." J Cereb Blood Flow Metab. 1 June 2026. doi: 10.1177/0271678X261454172.