13-Hydroxy-LSD is a lysergamide and a metabolite of the psychedelic drug lysergic acid diethylamide (LSD). It is a major metabolite of LSD in rats and guinea pigs but a minor metabolite of LSD in monkeys and humans. Following its formation, 13-hydroxy-LSD undergoes further metabolism via glucuronidation. Little is known about the specific enzymes responsible for generation of LSD metabolites such as 13-hydroxy-LSD in humans.
According to David E. Nichols in 2016, the pharmacology of hydroxylated metabolites of LSD like 13-hydroxy-LSD has not been studied. Nichols has posited that metabolism of LSD into active metabolites with potent dopamine receptor activity may be responsible for the delayed-onset dopaminergic stimulus effects of LSD in rodent drug discrimination tests. Relatedly, lergotrile's corresponding metabolite 13-hydroxylergotrile is 100-fold more potent as a dopamine receptor agonist than lergotrile itself in vitro. However, more research is needed to assess the activity of 13-hydroxy-LSD and its potential involvement in LSD's effects. In any case, 13-hydroxy-LSD has been reported to produce LSD-like electroencephalogram (EEG) changes in rabbits.
Subsequently, 13-hydroxy-LSD was shown by Nichols and colleagues in 2026 to be an extremely potent dopamine D4 receptor agonist, with an of 36pM and 380times greater potency than LSD itself (which had a value of 14nM). Moreover, 13-hydroxy-LSD is among the most potent dopamine D4 receptor agonists ever to have been discovered. While 13-hydroxy-LSD is only a minor metabolite of LSD in humans, it is so potent as a dopamine D4 receptor agonist that it may contribute to LSD's effects and may indeed be responsible for the delayed dopaminergic or "paranoid" phase of LSD's effects.
The 13 position of the ergoline ring system as in LSD and 13-hydroxy-LSD corresponds to the 6 position of the indole ring as in simple tryptamines. 6-Hydroxy-DMT has been found to be active but less potent than dimethyltryptamine (DMT) in animals and to be inactive in humans at the assessed doses. "6-HO-DMT is a minor metabolite of DMT in man, and it was studied for the same reasons. Could this compound play a role in explaining the activity of the parent dialkylamine? It was explored in a series of subjects who had responded spectacularly to DMT. The five volunteers in this study were former opium addicts who were serving sentences for violation of United States narcotics laws. They were administered 6-HO-DMT at either 0.75 mg/kg (one subject) or 1.0 mg/kg (four subjects) and reported no differences from the inactive placebo control. The objective measures (blood pressure, respiration and heart rate, pupillary dilation) confirmed this absence of activity at this level. The active control drug was DMT itself, and it showed the expected responses in all regards." [...] "It is pretty generally accepted that 6-HO-DMT is inactive. I am not too surprised. There are so few things with open and exposed hydroxyl groups that succeed in making it through the lipid barriers that protect to the brain." Similarly, it showed very low affinity for the serotonin 5-HT2 receptors.
13-Hydroxy-LSD was first described in the scientific literature by at least 1963.
See also Substituted lysergamide LSD § Psychological (two phases of effects) Psychedelic microdosing § Neurological toxicity 13-Methoxy-LSD 12-Hydroxy-LSD 14-Hydroxy-LSD 6-Hydroxy-DMT 2-Oxo-LSD 2-Oxo-3-hydroxy-LSD
References
External links 13-OH-LSD - Isomer Design