13-Hydroxy-LSD

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 several-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, metabolites of LSD, possibly including 13-hydroxy-LSD, have been reported to be pharmacologically active with LSD-like effects in animals, although details do not appear to have been provided.

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. 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.