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What it does - plain English
Semax is a synthetic seven-amino-acid peptide (a short chain of protein building blocks) based on a fragment of ACTH - adrenocorticotropic hormone, the hormone your pituitary gland releases to tell your adrenal glands to make cortisol. The Russian researchers who developed it modified the natural ACTH fragment to remove the cortisol-stimulating effect while keeping the brain-acting effects.
Result: a peptide that increases BDNF (brain-derived neurotrophic factor, a protein that supports the growth and survival of neurons) without raising cortisol. Approved in Russia for stroke recovery and cognitive support. Used off-label by the nootropic community for focus and mental endurance. Most often administered as an intranasal spray.
Status
B-tier within cognitive peptides. The Russian neuroprotection and stroke-recovery data is methodologically reasonable, with multiple trials over decades. The neurotropic and BDNF mechanism is well-supported. As with Selank, Western replication is sparse and the trials are concentrated in one research tradition.
The peptide community treats Semax and Selank as the most-evidence-supported Russian cognitive peptides. That is a meaningful distinction in a field where most compounds have almost nothing behind them.
Legal status
Approved as a prescription medication in Russia for cerebrovascular disorders (conditions affecting blood flow to the brain), cognitive impairment, and asthenia (a clinical term for chronic fatigue or weakness). Not FDA-approved in the US. Not banned. Research-peptide category in the US.
The gap between Russian approval and US status is not unusual for this class of compound. Russia has a longer history of state-funded neuroprotection research, and several compounds that are Rx there have no equivalent Western review pathway.
Where to source
Two paths: international pharmacy import from Russia (legal for personal use in some states, gray zone in others) or research peptide vendors with a COA (Certificate of Analysis - the lab report verifying purity and concentration).
The pharmaceutical-grade nasal spray formulation is what the Russian trials use. Research-grade Semax from US peptide vendors may not be in the same formulation. Always ask for a COA. No COA, no buy.
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Two studies worth reading
Stroke recovery RCT
Gusev, E. et al., Zhurnal Nevrologii i Psikhiatrii imeni S.S. Korsakova
Russian trial of acute ischemic stroke patients receiving Semax adjunctively to standard care. Improvements in neurological recovery scores compared to standard care alone. The trial that anchors the stroke-recovery indication in Russia.
BDNF-induction mechanism study
Dolotov, O. et al., Brain Research Bulletin
Mechanism paper showing Semax increases BDNF in the rat hippocampus - the brain region central to memory and learning. The molecular basis for the cognitive-support claim.
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Last reviewed · 2026·05·04 · Status reviewed weekly