It is a quiet day on the research wire, which affords us the welcome excuse to look backwards — specifically, to a clinical research programme at the University of New Mexico that, between roughly 1990 and 1995, did more to shape the modern scientific conversation about N,N-dimethyltryptamine than any work before or since. Rick Strassman's DMT studies were not the first to administer the compound to humans; that distinction belongs to the Hungarian chemist and psychiatrist Stephen Szára, who injected himself with it in 1956. But Strassman's programme was the first systematic attempt to apply something approaching contemporary clinical pharmacology to the experience, and its influence on the field's vocabulary, dosing conventions, and phenomenological categories remains pervasive — for better and, one might argue, for worse.

Context: A Twenty-Year Drought

By the late 1980s, human psychedelic research in the United States had been effectively dormant for two decades. The regulatory chill that followed the Controlled Substances Act of 1970 had not technically prohibited such studies, but the practical barriers — Schedule I licensing, Institutional Review Board wariness, the reputational risk to any investigator foolish enough to try — amounted to a de facto moratorium. Strassman's achievement was in part bureaucratic: obtaining FDA approval, DEA Schedule I researcher registration, and university ethics clearance for a dose-response study of intravenous DMT in healthy volunteers. The paperwork alone is reported to have taken approximately two years. One sometimes forgets that the enabling infrastructure of a study can be as consequential as the science itself.

Design and Dosing

The core protocol involved the intravenous administration of DMT fumarate to experienced hallucinogen users — a deliberate choice intended to reduce the risk of panic reactions in naïve subjects. Doses were administered across a range: 0.05, 0.1, 0.2, and 0.4 mg/kg, delivered as a bolus injection over approximately 30 seconds. A saline placebo condition was included. The intravenous route was chosen for its pharmacokinetic clarity: rapid onset (effects within seconds), short duration (peak at roughly two to five minutes, substantial resolution by 20–30 minutes), and relatively precise dose control compared to smoked or intramuscular administration. The programme is reported to have enrolled approximately 60 volunteers across its various phases, including an extended dosing sub-study examining tolerance.

Physiological monitoring included heart rate, blood pressure, rectal temperature, pupil diameter, and neuroendocrine measures — notably plasma beta-endorphin, cortisol, prolactin, growth hormone, and melatonin levels. The Hallucinogen Rating Scale (HRS), developed by Strassman and his colleagues specifically for this work, provided the primary subjective outcome measure. The HRS comprised six clusters: Somaesthesia (interoceptive and bodily effects), Affect (emotional responses), Perception (visual, auditory, and other sensory changes), Cognition (alterations in thought content and process), Volition (sense of self-control and agency), and Intensity (overall strength of the experience). This taxonomy was born of necessity — no existing psychiatric rating instrument was adequate to the phenomenology — and it has persisted in the field with little modification.

What Emerged

The dose-response data were orderly: subjective effects scaled with dose in a manner that was, by the standards of psychiatric pharmacology, unusually clean. The 0.4 mg/kg dose reliably produced full immersive experiences — the now-familiar reports of encounters with entities, passage through tunnels or geometric spaces, dissolution of self-world boundaries. The 0.05 mg/kg dose produced threshold somatic effects with minimal perceptual change. Neuroendocrine responses were similarly dose-dependent, with significant elevations in cortisol, ACTH, and beta-endorphin at higher doses. Cardiovascular effects — principally increases in systolic blood pressure and heart rate — were transient but notable, peaking within two minutes and resolving within 20.

The tolerance sub-study, in which subjects received four successive 0.3 mg/kg doses at 30-minute intervals, found no significant diminution in subjective effects across administrations — a finding that distinguished DMT from LSD and psilocybin, where acute tolerance develops rapidly. It continues to intrigue pharmacologists exploring receptor desensitisation kinetics.

The Taxonomy's Long Shadow

Strassman's phenomenological categories — the entity encounters, the "waiting room," the sense of arrival in an independently existing space — entered the cultural and scientific lexicon largely through his 2001 book DMT: The Spirit Molecule, which drew on the clinical data but framed it within a speculative metaphysical architecture involving the pineal gland and endogenous DMT release at birth and death. The scientific community's relationship with this framing has been, to put it diplomatically, complicated. The clinical pharmacology was sound; the pineal hypothesis was not well supported by evidence then and remains poorly supported now. Yet the two became entangled in the public imagination, and subsequent researchers have had to navigate a landscape in which Strassman's careful dose-response curves and his more adventurous theorising are often treated as a single package.

What endures most usefully is the HRS itself and the basic pharmacokinetic and dosing parameters. The 0.3–0.4 mg/kg intravenous dose range established in Albuquerque remains the reference standard for contemporary human DMT studies — including the Imperial College and University of Michigan programmes now exploring extended-state DMT infusion. The six-cluster phenomenological model, while debatable in its granularity, gave researchers a shared descriptive framework where none had existed. One can quarrel with the categories and still acknowledge their utility.

What Current Research Still Wrestles With

Several open questions trace directly back to gaps or ambiguities in the Strassman data. The absence of acute tolerance remains incompletely explained at the receptor level; sigma-1 receptor involvement, 5-HT2A receptor trafficking dynamics, and trace amine-associated receptor (TAAR) contributions have all been proposed, none conclusively. The phenomenological consistency of entity encounters across subjects — Strassman reported that roughly half of volunteers at the 0.4 mg/kg dose described contact with seemingly autonomous beings — raises questions about the neural correlates of "perceived presence" that current neuroimaging protocols are only beginning to address. And the basic safety pharmacology, while reassuring within the studied population of healthy, experienced volunteers, tells us rather less than we need to know about cardiovascular risk in the broader populations now being considered for therapeutic trials.

The Strassman protocol was, in essence, a careful first pass: proof that the compound could be studied rigorously in humans, that dose-response relationships were orderly, and that the phenomenology, however extraordinary, submitted to systematic description. That it was also the last pass for nearly two decades says more about the regulatory and cultural environment than about any scientific deficiency in the work itself.

Marginalia

The most cited finding from Strassman's programme — the entity encounter — was never the primary endpoint. It emerged as a recurrent qualitative theme, was reported with appropriate caution, and then took on a life of its own. There is a lesson here about which findings survive contact with the public, and it has little to do with p-values.