Semax: Legal Status, Side Effects, and Human Evidence

Semax is a synthetic heptapeptide, Met-Glu-His-Phe-Pro-Gly-Pro. It is an analog of ACTH(4-10), a fragment of adrenocorticotropic hormone. It was studied for effects on learning and for brain protection after ischemia, and it is often described as a nootropic. It was developed in Russia, where a 2022 review lists it among registered peptide drugs. Registration there does not establish approval or evidence acceptance elsewhere, and it is not an approved medicine in the United States or Canada.

Animal studies: in the rat hippocampus, a single application raised levels of the growth factor BDNF and the activation of its receptor, trkB, and treated rats made more conditioned avoidance responses. After an experimental blockage of a brain artery in rats, Semax increased cortical transcription of neurotrophins, including BDNF and NGF, and of their receptors. A genome-wide rat study found changes in genes linked to the immune and vascular systems.

In rodents, Semax raised a serotonin metabolite in the striatum without changing dopamine on its own, and it enhanced the dopamine release and movement caused by D-amphetamine. These are hypotheses about how it might act in people, not shown human mechanisms.

The one human study in this entry is a 2018 Russian study of 110 patients in early or late rehabilitation after ischemic stroke. Each group was split into patients who did or did not receive Semax. The Semax subgroups had higher blood BDNF and better recovery on the Barthel index, a scale of daily-living function. The abstract does not describe randomization or blinding, so it is weak evidence of benefit.

None of these studies tests cognition, focus or memory in healthy people. Claims about brain fog, ADHD, anxiety or depression are not supported by controlled human trials in this entry.

Human safety data are thin. The stroke study was small and short, and it was not designed to detect rare or long-term harms. Interactions with stimulants or other drugs that act on dopamine and serotonin have not been studied in controlled human trials. The rodent finding that Semax amplified amphetamine-driven dopamine release is a reason for caution, not a measured human risk.

FDA says compounded drugs containing Semax may pose a risk of immunogenicity for some routes, because of possible aggregation and peptide-related impurities, and that it has no, or limited, safety information for the proposed routes.

Semax is not approved by the FDA or Health Canada, and Health Canada's Drug Product Database lists no product containing it. FDA lists it among bulk substances nominated for compounding that were placed in category 2 and then withdrawn by the nominators. It is not named on the 2026 WADA Prohibited List, whose section S0 covers substances with no current approval by any government health regulator for human therapeutic use.