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LSD

Group: Psychedelics
Nicknames: lysergic acid diethylamide, acid, tab, blotter, L, Sid, lucy, LSD-25
Last reviewed: October 2026

Pharmacology

LSD is a non-selective serotonin receptor modulator. This includes potent serotonin 2A (5-HT2A) receptor activation, thought to be primarily responsible for its psychedelic effects. However, its activation of other serotonin receptors may modulate its subjective effects, alongside its dopamine receptor affinities – unique among serotonergic psychedelics.

LSD is one of the most potent psychedelics in humans, with typical doses of 30–70 µg. Its oral bioavailability is around 80%, takes an average of 1.5 hours to reach its peak blood concentration after consumption, and has a half life of around 3–5 hours. That said, LSD gets temporarily ‘trapped’ inside the serotonin receptor. While LSD in the bloodstream gets quickly broken down by CYP450 liver enzymes, plenty of LSD continues to activate the psychedelia-inducing brain receptors making ‘trips’ last typically between 6 and 12 hours, depending on dose, tolerance and age. In individuals who are CYP2D6 poor metabolisers, or people taking CYP2D6 inhibitors, LSD’s half life increases to around 8 hours.

Although LSD binds tightly to the 5-HT2A receptor, the maximum pharmacological effect it causes is lower than that for other similar drugs and once that maximum ‘ceiling’ is reached, further stimulation of these receptors is blocked. For this reason, LSD is described as a ‘strong partial agonist’ at the 5-HT2A receptor.

In contrast with other psychedelic drugs that bind to serotonin receptors, LSD also binds to, and stimulates many dopamine receptors. This binding is thought to stimulate some of the non-psychedelic effects of LSD.

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