A unique psychedelic shows promise for pain and stroke

An unusual psychedelic compound found in the plant Salvia divinorum has shown potentially useful effects against pain, addiction, and stroke in animal experiments, although side effects remain a major barrier. The systematic review was published in the journal Translational Psychiatry and found much less consistent evidence for treating depression. The compound, salvinorin A, differs markedly from substances such as psilocybin and LSD. Those better-known psychedelics primarily affect the brain’s serotonin signaling (how the brain uses the chemical messenger serotonin to regulate mood and perception). In contrast, salvinorin A acts mainly through a different system known as the kappa opioid receptor, which is a specific protein in the brain involved in pain, mood, and consciousness. This distinction has attracted researchers interested in developing treatments that work through pathways not targeted by classical psychedelics. Laboratory experiments have investigated salvinorin A in conditions ranging from pain and drug addiction to depression and reduced blood flow to the brain (such as during a stroke). Yet the evidence was scattered across different species, doses, and experimental models. Human therapeutic trials—testing the drug in human patients—are scarce, making it difficult to determine whether promising animal findings justify further clinical development. Led by Wolfgang Emanuel Zürrer at the University of Zurich, the researchers systematically searched three major scientific databases for relevant animal studies published up to June 28, 2024. They screened 1,718 publications and included 82 studies in their descriptive review, with 10 providing sufficiently comparable data for a meta-analysis (a statistical method that combines the results of multiple studies to find overarching trends). The studies collectively used about 3,456 animals. Rats accounted for the largest share, followed by mice, non-human primates, piglets, and zebrafish. Across the evidence, salvinorin A repeatedly reduced pain-related responses and inflammation, showed protective effects in experimental models of stroke and related brain injuries, and reduced some forms of drug-seeking behavior. Depression was a very different story. Some studies recorded behavior consistent with an antidepressant effect, while others found the opposite, including depression-like responses. Safety also produced a mixed picture. Animal studies reported anxiety-like behavior and problems with movement and cognition (thinking and memory skills), yet the compound generally had limited effects on vital physical measures like heart rate or blood pressure. Its extremely short action presents another challenge: depending on how it was given, concentrations peaked within seconds or minutes. Its measured brain half-life (the time it takes for half of the substance to break down and leave the brain) ranged from about three to 36 minutes, with elimination from the blood taking roughly an hour. The review also identified 16 chemically modified relatives of salvinorin A. Several lasted longer, entered the brain more effectively, or produced fewer unwanted behavioral effects in animals, suggesting that the parent compound might ultimately be more valuable as a starting point for drug development than as a medicine itself. The authors concluded, “Our findings support the therapeutic potential of salvinorin A for pain, addiction, and stroke, though its side effect profile may limit clinical application. The development of novel [compounds] could address these challenges.” However, some limitations are to be noted. For instance, animal models cannot reproduce the complexity of human psychiatric illness, the reviewed experiments varied substantially in design, and young male rodents dominated the evidence base (meaning the results might not perfectly translate to humans or to females). The study, “The translational potential of salvinorin A: systematic review and meta-analysis of preclinical studies,” was authored by Wolfgang Emanuel Zürrer, Lionel Wettstein, Helena D. Aicher, Milan Scheidegger, and Benjamin Victor Ineichen.