Repeated low doses of LSD were safe and well tolerated in healthy older adults
A 2019 phase 1 trial gave healthy older adults repeated low doses of LSD to check whether the doses were safe and well tolerated and how much drug reached the blood.
This was an early-stage safety test of very low doses of LSD in healthy older adults. Forty-eight volunteers, average age about 63, were split into four groups: a dummy-pill (placebo) group and 5-, 10-, and 20-microgram LSD groups. Each person took their assigned dose six times, once every four days over three weeks, and neither the participants nor the staff scoring them knew who got LSD. The doses were well tolerated: side effects happened about as often as with the placebo, the main difference being slightly more mild-to-moderate headaches on LSD. No one dropped out because of a side effect, and tests of thinking, balance, and body awareness showed no impairment. The lowest 5-microgram dose was too small to detect in the blood; the 10- and 20-microgram doses peaked in the blood at 30 minutes. The authors concluded the low doses were safe and well tolerated.
In this phase 1 randomized, double-blind, placebo-controlled dose-response study, 48 healthy older volunteers (mean age 62.9 years) were assigned to placebo (n = 12), 5 μg (n = 12), 10 μg (n = 12), or 20 μg (n = 12) LSD and received their assigned dose on six occasions, once every 4 days over 21 days. LSD was well tolerated: the frequency and intensity of adverse events were similar to placebo, and the only minor clinical difference was the number of headaches reported (8.3% of placebo volunteers versus 16.7%, 50.0%, and 25.0% at 5, 10, and 20 μg). No volunteer discontinued due to an adverse event and no unexpected adverse events occurred, and assessments of cognition, balance, and proprioception revealed no impairment. LSD plasma levels were undetectable in the 5 μg group; peak plasma levels for the 10 and 20 μg groups occurred at 30 minutes. The authors conclude the results support the safety and tolerability of these low doses.
The authors' interpretation is bounded by the pharmacokinetic data: they note that the estimate of how long LSD stayed in the blood (its half-life) was limited by very low plasma drug levels and incomplete data at time points after 4 hours for most volunteers, so drug-level conclusions carry limited certainty. Design-inherent points: this was a small first-step safety study (48 participants, only 12 per dose group) designed to assess safety, tolerability, and pharmacokinetics — not to test whether LSD treats or prevents any disease or symptom, so it says nothing about clinical benefit. The dosing period was short (21 days) with no long-term follow-up, and the sample was healthy older adults, not a clinical or veteran population, limiting generalizability. The study was funded by Eleusis Benefit Corporation, and all authors were paid consultants of the company.
In a phase 1 double-blind, placebo-controlled, randomized study, 48 healthy older volunteers received placebo, 5 μg, 10 μg, or 20 μg LSD on six occasions every 4 days over 21 days, and the authors concluded the results support the safety and tolerability of these low doses (Family et al., 2019, Psychopharmacology).
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