Then (1979), LSD: My Problem Child
LSD Potency: The Threshold Claim
LSD was the most potent psychoactive substance known, active in extremely small amounts, making it roughly 1,000 times more potent than mescaline and 10,000 times more potent than psilocybin by weight.
confirmed
LSD remains the most potent classical psychedelic in clinical use. However, more recently characterized compounds, particularly 5-MeO-DMT, which is active in very small amounts by inhalation, produce comparable experiences at even lower weights. The 5-HT2A binding affinity of LSD and its unusual 'lid' mechanism (the drug becomes trapped in the receptor for hours, explaining its duration) were elucidated by crystal structure studies in 2017 (Wacker et al., Cell). The mechanism Hofmann could only speculate about is now resolved at atomic resolution.
Sources
- Hofmann, LSD: My Problem Child (1979)
- Wacker et al., Cell (2017)
- Nichols, Pharmacol. Rev. (2016)