Psychological and physiological effects of extended DMT

Luan and colleagues frame N,N-dimethyltryptamine (DMT) as a fast-acting serotonergic psychedelic that produces a brief but intense altered state of consciousness, often described as immersion into an alternate world and sometimes involving encounters with apparent 'entities'. Earlier work has used bolus intravenous (IV) administration, inhalation or the oral preparation ayahuasca; IV bolus dosing offers precise control but produces effects that peak within two to three minutes and largely subside within about 30 minutes. The brief time-course limits opportunities to study sustained phenomenology and neurobiology, and no pharmacokinetically informed continuous IV DMT protocols had been systematically tested in humans prior to this study. This study set out to develop and test a bolus-plus-constant-rate IV infusion method intended to prolong and stabilise the DMT experience for 30 minutes. The investigators aimed to derive infusion regimens from prior pharmacokinetic data to maintain moderate-to-high levels of subjective immersion while monitoring psychological safety and physiological responses, thereby creating a platform for extended experimental and potentially therapeutic applications of DMT.

The study used a single-blind, within-subjects, placebo-controlled repeated-measures design. Eleven healthy, psychedelic-experienced volunteers attended multiple dosing visits separated by at least two weeks; up to four different bolus-plus-infusion DMT dose regimens were tested across participants. EEG and pharmacokinetic modelling are reported elsewhere; the present report focuses on subjective, autonomic and plasma outcomes. Dose regimens were derived from a population pharmacokinetic reanalysis of prior bolus IV DMT data and implemented as a bolus injection delivered over 30 seconds followed, after one minute, by a constant-rate infusion lasting 29 minutes (total 30 minutes of DMT administration). A pilot 1.5 mg + 0.2 mg/min session was used for safety and excluded from analysis. The first analysed regimen began with a 6 mg bolus plus a 0.63 mg/min infusion and subsequent sessions escalated when prior doses were well tolerated and produced average peak subjective intensity < 7.5 (0–10 scale). Doses tested in the study reached up to 18 mg bolus + 1.9 mg/min according to the authors. Procedures on dosing days included baseline physiological measures, EEG cap placement, cannulation on both arms (one cannula for blood sampling, the other for infusion), and supportive measures such as a body scan and low-volume ambient music; participants kept eyes closed and wore an eye mask during dosing. Acute subjective intensity was sampled verbally in response to audio prompts at -8, -6, -4, -2, 0, 1, 2, 3, 4 and every two minutes thereafter up to 52 minutes from bolus start. Anxiety ratings were obtained every four minutes. Retrospective measures were collected approximately 30 minutes after the end of administration and included the 5D-ASC (94 items) and MEQ-30. Heart rate (HR) was monitored minute-by-minute using an Empatica E4 wristband. Plasma DMT was measured from repeated blood samples taken at baseline and multiple post-bolus timepoints; the extracted text does not clearly report all specific sampling times, though results refer to early samples (around minute 2) and later samples up to minute 29 and beyond, with additional sampling up to 180 minutes mentioned ambiguously. For analysis, the investigators fitted linear mixed-effects models (LMMs) in R using lme4 and lmerTest, controlling for participant ID as a random intercept. For time-varying measures (intensity, anxiety, HR, plasma concentrations) dose and timepoint were fixed effects and outcomes were analysed as change scores from the subject’s placebo at the same timepoint; dose and time were treated as categorical with minute -8 of Dose 1 as reference. For non-temporal measures (5D-ASC, MEQ-30), separate LMMs per subscale included Dose as a fixed effect on raw scores. False discovery rate correction was applied and significance was set at p < 0.05. The authors did not statistically analyse retrospective dynamic ratings over time due to recall-bias concerns.

Eleven volunteers contributed data across dose levels: six participants received Dose 1, ten received Dose 2, nine received Dose 3, and five received Dose 4. Adverse reactions are described in a table referenced in the text but not reproduced in the extracted material. Acute subjective intensity increased rapidly with all tested doses. Effects began within the first minute of the bolus and peaked at minute 2, after which intensity remained relatively stable throughout the infusion period. LMMs showed a significant increase in intensity for Dose 1 versus placebo at minute 1 (β = 5.33, t = 15.5, p < 0.001), with peak intensity at minute 2 (β = 5.50, t = 15.9, p < 0.001) and a sustained effect until minute 42 (β = 0.83, t = 2.35, p = 0.026). Significant dose–response increases relative to Dose 1 were reported for Dose 2 (β = 1.09), Dose 3 (β = 1.85) and Dose 4 (β = 3.12), all p < 0.001, yielding a significant dose–effect relationship during the 30-minute infusion and for 12 minutes after infusion end (all FDR corrected). Anxiety ratings remained generally low before and during dosing, indicating tolerability. LMMs found no significant dose-related increases in anxiety; small significant differences versus placebo occurred at minutes 8, 12 and 28 (β ≈ 0.60–0.70, p-values 0.019–0.008, FDR corrected) that the authors attribute to a quicker drop in anxiety in the placebo condition and to anticipatory effects rather than dose-dependent drug effects. Retrospective assessments showed robust altered-consciousness and mystical-type effects. On the 5D-ASC, 'Oceanic boundlessness' and 'Visionary restructuralization' increased significantly for all doses versus placebo; 'Dread of ego-dissolution' and 'Auditory alterations' increased only for some higher doses. For the 11D-ASC several subscales increased significantly for all doses (for example 'Unity', 'Meaning', 'Spiritual experience', 'Blissful state', 'Insightfulness', 'Complex imagery', and 'Elementary imagery'), with 'Disembodiment' and 'Impaired cognition' increasing only at higher doses. No dose differed from placebo on certain subscales such as 'Anxiety' and 'Audio/visual synesthesia'. The MEQ-30 total and all subscales increased significantly for all doses relative to placebo. Heart rate rises followed a rapid temporal profile: Dose 1 produced HR increases starting at minute 0 (β = 8.29, t = 2.75, p = 0.013), peaking at minute 2 (β = 35.5, t = 11.8, p < 0.001) and remaining elevated until minute 24 (β = 8.95, t = 2.97, p = 0.007). Dose-related additions were significant after FDR correction for Dose 3 (β = 4.28, p = 0.003) and Dose 4 (β = 8.67, p < 0.001). The authors report that HR habituated within about 10–15 minutes while subjective effects stayed elevated. Plasma DMT concentrations rose sharply after the bolus, with an early peak at minute 2 (β = 103.4, t = 14.2, p < 0.001) and a second peak around minute 29 (β = 124.2, t = 17.1, p < 0.001) that coincided with late sampling during infusion. Higher doses produced larger plasma concentrations compared with Dose 1 (Dose 2 β = 11.7, p = 0.019; Dose 3 β = 35.2, p < 0.001; Dose 4 β = 45.8, p < 0.001), with significant dose effects up to minute 50 (FDR corrected). Plasma levels dropped quickly after infusion end, reaching < 1 nM by 90 minutes. The authors note a dissociation from about minute 20 onward: plasma concentrations continued to rise while subjective intensity remained plateaued or declined slightly, a pattern they interpret as suggesting short-term psychological tolerance or habituation.

Luan and colleagues interpret their findings as demonstration that a bolus-plus-constant-rate IV infusion can extend and stabilise the typically brief DMT experience for a chosen 30-minute window. Subjective effects emerged within one minute, peaked at two minutes, and then settled at a sustained, slightly lower-than-peak level during infusion. Intensity increased in a dose-dependent manner while anxiety remained low overall, with only transient anticipatory increases. Heart rate rose rapidly after the bolus but habituated within about 10–15 minutes, which the authors present as evidence of physiological safety during extended infusions. A notable observation was the decoupling between rising plasma DMT concentrations and stable or slightly declining subjective intensity from around minute 20 onwards. The investigators suggest this reflects acute psychological tolerance or habituation to sustained stimulation—sharp transitions (such as from the bolus) may provoke stronger subjective responses than sustained levels of the same intensity. They acknowledge inter-individual variability in both plasma concentrations and subjective responses, reporting roughly a two-fold range for a single dose, and note that such variability is not unique to DMT but argues for personalised dosing approaches. Limitations discussed include the reliance at study conception on plasma concentration data from a single prior bolus study, meaning the pharmacokinetic model used to derive infusion regimens can be refined. The authors highlight that EEG and full PK–PD modelling are to be reported elsewhere and that the present sample size and exploratory dose-escalation nature limit definitive conclusions. They also point out variability between individuals as an uncertainty to be addressed in future work. Looking forward, the authors propose that refined PK–PD modelling and personalised infusion parameters could reduce variability and better maintain desired subjective states. They suggest potential applications in consciousness research (for example studying 'entity' experiences) and in clinical settings, where short half-life and rapid resolution after infusion may offer safety advantages over longer-acting oral psychedelics. The study is presented as a pilot demonstration of feasibility and safety that lays groundwork for longer infusions, dynamic dosing regimens and precision approaches in psychedelic research and therapy.