Safety, tolerability and subjective effects of vaporized N,N-Dimethyltryptamine: A randomized double-blind clinical trial.

Vaporized N,N-Dimethyltryptamine (DMT) has a short duration and simple application, prompting this technique as a new approach for psychedelics' clinical use. Building on our initial dose-ascending studies and addressing potential confounding effects of dosing order, this study is the first to evaluate inhaled DMT in a randomized, placebo-controlled, double-blind design. Given DMT's therapeutic potential, we aimed to assess its safety, tolerability, and subjective effects compared to an active placebo. Twenty-five healthy participants completed two treatment sessions, receiving DMT (60 mg) or active placebo (0.6 mg DMT) in a crossover design with a two-hour interval between the sessions. Subjective experiences were evaluated using measures of intensity and valence, the Five Dimensions of Altered States of Consciousness Questionnaire (5D-ASC), the Hallucinogen Rating Scale (HRS), and the Mystical Experiences Questionnaire (MEQ). Physiological parameters were monitored, including systolic and diastolic blood pressure, heart rate, respiratory rate, and peripheral oxygen saturation. Biological responses were analysed through various biochemical biomarkers. Adverse events were recorded. Compared to placebo, DMT significantly increased subjective measures of intensity, as well as most 5D-ASC, HRS, and MEQ factors, except for 5D-ASC Anxiety, Audio-Visual Synaesthesia and Vigilance Reduction subscales. DMT transiently increased physiological parameters within safe limits. Biochemical changes were not clinically relevant. The adverse events were predominantly mild and transient. Physiological increases were significantly correlated with subjective experiences, providing insights into the interaction between physiological responses and altered states of consciousness. Our findings suggest that inhaled DMT is safe, well-tolerated, and capable of inducing profound altered states of consciousness. Clinicaltrials.gov NCT05901012.