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About this resource
This page introduces a 1999 study that measured blood concentrations and time courses of major alkaloids in humans after exposure to an ayahuasca-type brew called hoasca in Brazil. Fifteen healthy, experienced participants took part in a ceremonial context, and the brew and plasma were analyzed for DMT, harmine, harmaline, tetrahydroharmine, and related constituents.
Study design
Participants consumed a defined amount of hoasca and then underwent blood collection and subjective assessments at several time points. Gas chromatography and high-performance liquid chromatography were used to measure constituent content in the brew and plasma concentrations. There was no placebo or alternative comparison condition; the study primarily described pharmacokinetics.
Content
The mean time to peak blood concentration of DMT was reported as approximately 107.5 minutes, and strong subjective effects broadly corresponded with the period of higher alkaloid concentrations. The findings support the pharmacological explanation that DMT, which is ordinarily readily broken down when taken orally, reaches the systemic circulation when combined with monoamine oxidase inhibition by β-carbolines.
Each constituent had a different rate of absorption, metabolism, and elimination. A brew is a mixture of multiple constituents, and DMT concentration alone cannot explain the overall effects. Exposure also changes when constituent concentrations differ between samples, even at the same volume.
Results
This is an early resource that quantified hoasca-derived alkaloids in humans and showed their temporal correspondence with acute subjective effects. It became a foundation for later research using standardized preparations and investigating interactions. Understanding pharmacokinetics, however, is not the same as establishing efficacy or long-term safety.
Limitations
This was an uncontrolled study of 15 experienced participants. Analytical methods from the 1990s had the detection and quantification constraints of their time and may not always be directly comparable with current measurements. Results from a single ceremony and sample cannot be generalized to diverse ayahuasca preparations or first-time participants.
Without a placebo condition, the temporal parallel between subjective effects and blood concentrations cannot establish every detail of causation. The true peak concentration may also have occurred between blood-draw time points, so the reported time to peak depends on the sample and measurement schedule. A research condition defined by body weight is not a conversion standard for uncharacterized samples used elsewhere.
Safety
Individual differences in pharmacokinetics make the strength and duration of effects difficult to predict. Enzyme inhibition by β-carbolines may be relevant to interactions with concomitant medications and other substances. A small monitored study of healthy, experienced participants does not establish safety in cardiovascular disease, psychiatric illness, pregnancy, or other conditions.
The time at which constituents disappear from blood is not necessarily the time at which judgment and mental state have fully returned to baseline. Curves of acute pharmacology alone cannot evaluate accidents, delayed psychological difficulties, or effects of repeated use. This page is not a resource for selecting an amount to ingest.
Average values conceal the range among people with faster or slower absorption and metabolism. Liver function, enzyme activity, other drugs, and differences in brew concentration can alter the time course. Representative values from an older study cannot predict the onset or end of effects in an individual.
Pharmacokinetics is not a study that defines a safety margin; it describes movement through the body under the measured conditions.
The reported values should therefore be treated as historical and pharmacological reference points, not transferred directly to another sample or person. This study must also be distinguished from research on clinical outcomes.
Source and rights
Original source: Callaway JC, et al. Pharmacokinetics of Hoasca alkaloids in healthy humans. Journal of Ethnopharmacology. 1999;65(3):243–256. DOI: 10.1016/S0378-8741(98)00168-8.
This page is a detailed introduction based on publicly available bibliographic information and the abstract; it is not a translation or republication of the copyrighted article. Consult the original for measurement methods and individual numerical results.