Peptide Health Lab

Cognitive & neuro

Semax

FOR RESEARCH PURPOSES ONLY

Also known as: ACTH(4-7)-Pro-Gly-Pro, Met-Glu-His-Phe-Pro-Gly-Pro

Regulatory status
Research only
Evidence grade
Anecdotal reports only

Last reviewed September 1, 2026 · 12 sources

What Semax is and how it works

Semax is a synthetic heptapeptide: the 4–7 fragment of adrenocorticotropic hormone, Met-Glu-His-Phe, extended at the C-terminus with the tripeptide Pro-Gly-Pro. The extension is the design decision. Short peptides are cleared from blood in minutes, and appending Pro-Gly-Pro slows enzymatic degradation enough for the molecule to survive long enough to act. Everything the compound is known to do rests on that fragment being a melanocortin sequence stripped of the hormonal activity of full-length ACTH.

The proposed mechanism is neurotrophic rather than transmitter-like, and the work behind it is careful. In rat basal forebrain, tritium-labelled peptide bound cell membranes in a way that was time-dependent, specific, reversible and dependent on calcium ions, with a dissociation constant of 2.4 nanomolar and a maximum binding capacity of 33.5 femtomoles per milligram of protein.[1] Intranasal application at 50 and 250 micrograms per kilogram raised brain-derived neurotrophic factor protein in that same region within three hours, and did not raise it in the cerebellum.[1] In the hippocampus, a single 50 micrograms per kilogram application raised BDNF protein about 1.4-fold and trkB tyrosine phosphorylation about 1.6-fold.[2] Further in vivo work reported stimulated BDNF expression across several regions of the rat brain.[3]

A second proposed mechanism is monoaminergic modulation. In rodents, striatal 5-hydroxyindoleacetic acid rose about 25% in tissue two hours after administration and extracellular 5-HIAA climbed to roughly 180% over one to four hours, while dopamine and its metabolites were unchanged by the peptide given on its own.[6]

Both mechanisms are proposed rather than established, and both are described in rats. There is no published human receptor-binding, neurochemical, or pharmacokinetic study of this compound. What a 2.4-nanomolar binding constant measured in rat basal-forebrain membranes predicts about a human brain is a question the literature has not asked.

What the research actually shows

The clinical literature is stroke, and it is not randomized. A 1997 study gave the peptide to 30 patients in the acute period of hemispheric ischemic stroke, alongside combined intensive therapy, and compared them against 80 patients with strokes of comparable severity and lesion location receiving conventional therapy. Using clinical rating scales, EEG mapping and somatosensory evoked potentials, the authors reported that including the peptide had some influence on the rate of restoration of the damaged neurological functions, in the form of increased regress of general cerebral and focal disorders, motor disorders especially, and identified 12 mg per day for moderate strokes and 18 mg per day for severe ones as the most effective daily doses over 5- and 10-day courses.[8] The study is indexed as a controlled clinical trial. It is not described as randomized, and it is not described as blinded.

The 2018 rehabilitation study is the most-cited human result and it has the same shape. One hundred and ten patients after ischemic stroke were divided into early rehabilitation (89 ± 9 days) and late rehabilitation (214 ± 22 days) groups, and each group was subdivided into subgroups that did and did not receive the peptide, at 6000 mcg per day in two 10-day courses separated by 20 days. The authors reported that administration raised plasma BDNF and kept it high through the study, and that the peptide and high BDNF together accelerated and improved the final Barthel index score, with a smaller effect on the degree of paresis.[9] Those are real reported findings and they deserve to be stated with their numbers. The abstract describes no randomization, no blinding, and no placebo, and does not say how patients were allocated to its "semax+" and "semax−" subgroups.

A 2024 Russian-language review reads that literature as positive. It concludes that the oligopeptide is clinically effective in ischemic stroke in both the acute and the recovery period, in atherothrombotic and cardioembolic subtypes, and across carotid and vertebrobasilar territories.[10] It is a narrative review of the same body of work described above, published in the same journal, and it is evidence of how that community reads its own literature rather than an independent appraisal of it.

The preclinical ischemia work is genuinely substantial. In rats with permanent middle cerebral artery occlusion, genome-wide transcriptional analysis found the peptide predominantly enhanced immune-system gene expression, with immune-response genes making up more than half of everything it altered at 24 hours, and changed the expression of 24 vascular-system genes at 3 hours and 12 at 24 hours.[4] In a transient-occlusion model, brain protein profiling found upregulated active CREB in subcortical structures including the ischemic focus, and downregulated MMP-9, c-Fos and active JNK.[5] These are mechanism studies. Gene and protein expression changed in the direction the authors predicted; no animal behavioural outcome is claimed by either.

Where the evidence is weak

The gap between what was studied and why people read this page is the whole story. Every human efficacy result above was generated in stroke patients in Russian hospital rehabilitation settings. The reason most readers arrive at a page about Semax is nootropic self-experimentation in a healthy adult brain — sharper focus, better memory, faster recall. Not one cited paper addresses that. The distance between "unblinded Barthel index recovery in a rehabilitation cohort" and "a healthy person thinks more clearly" is not a matter of degree; it is a different question, in a different population, with a different outcome measure.

The only placebo-controlled work in healthy people measured pictures of the brain, not what it did. Two studies come closest to the reader's question and both stop short of it. In 24 healthy volunteers of mean age 44, resting-state functional MRI before and 5 and 20 minutes after a single intranasal administration found a greater volume of the rostral, medial-frontal subcomponent of the default mode network in the 14 who received the peptide compared with the 10 who received placebo.[11] A second study in 52 healthy participants, with separate peptide, Selank and placebo arms, reported differences in resting functional connectivity between the right amygdala and a right-hemisphere temporal region.[12] Neither study administered a cognitive test as an endpoint. A changed resting-network topography is a demonstration that something reached the brain, not a demonstration that anything improved.

Gene expression is not an outcome. The rat transcriptomic and proteomic work is the most rigorous material on this page, and it is also the easiest to over-read. A gene whose expression rises after a drug is a fact about a molecular intermediate. The step from there to a benefit a person would notice has not been taken for this compound in any species, in any published study.

The research community is narrow. The preclinical mechanism work, the clinical work, the imaging work and the 2024 review that summarizes them all originate substantially from a small set of Moscow institutions and their collaborators, several sharing senior authors. No independent group outside that community has published a controlled trial of this compound, and the reviews that characterize the field are written from inside it.

Long-term human safety is unstudied. The published safety-directed work is a cell-culture screen in which the peptide at 0.1 and 10 micromolar increased mouse embryonic stem cell survival under serum deprivation and had little effect on differentiation into neuronal precursors.[7] No published study has followed a person taking this compound over months or years, and neither of the clinical studies above reports an adverse-event tally.[8][9] The rodent finding that the peptide sharply increased amphetamine's effect on extracellular dopamine and locomotion is the closest thing to an interaction signal the literature contains, and it is in rats.[6]

Legal and regulatory status

Semax is not approved by the FDA for any indication. There is no approved US product containing it, no approved labeling, and no assigned indication. Material carrying the name is distributed for laboratory research use, which is why this page carries research-only framing throughout.

The compounding position is more specific than "unapproved", and it is worth stating precisely. There was an attempt to make Semax (heptapeptide) lawfully available through compounding pharmacies: it was put forward for the section 503A bulks list, FDA placed it in category 2 of its interim policies — the category for substances the agency has identified as potentially presenting significant safety risks — and whoever put it forward then withdrew it, so the evaluation stopped there. FDA's stated concerns were the risk of immunogenicity for certain routes of administration arising from the potential for aggregation and peptide-related impurities, and that the agency had no or only limited safety-related information for the proposed routes of administration and therefore lacked sufficient information to know whether the drug would cause harm if administered to humans. The practical consequence is that Semax is not on the 503A bulks list and there is no lawful compounding pathway for it in the United States.

PHL was not able to confirm a marketing authorization for Semax against a primary regulatory register — the Russian State Register of Medicines has no interface this review could query — and reports that as the limit of what it verified rather than as a finding either way. What the record does establish is how the literature describes the compound: the published clinical work treats Semax as a registered medicinal product in the Russian Federation, and a 2024 review covers its place in the therapy and rehabilitation of patients with ischemic stroke, which is the setting every clinical result on this page comes from.[10] A status granted in another country is not a status in the United States; it belongs to a different regulator applying a different evidentiary standard. It is not an FDA finding, not a substitute for one, not an endorsement of the compound, and not a route to obtaining anything. PHL does not sell peptides and takes no position on how unapproved material reaches anyone.

Questions to bring to a provider

The productive conversation is not "should I run Semax". It is "here is the cognitive problem I am actually trying to solve — is it real, is it measurable, and is a peptide the right tool for it?" Questions worth raising:

  • Given that the human efficacy literature is unblinded stroke rehabilitation, what would count as evidence that this compound does anything in a healthy brain?[9]
  • The only placebo-controlled work in healthy adults measured resting-state brain imaging rather than memory or attention. Does a change in network topography mean anything a person would notice?[11]
  • Is there a treatable cause behind the cognitive complaint — sleep, thyroid, mood, medication, anaemia — that testing would identify before anything experimental is considered?
  • Does any current stimulant, dopaminergic or serotonergic medication change the calculus, given that rodent work found sharply amplified amphetamine responses?[6]
  • FDA's recorded concern about material carrying this name was immunogenicity arising from aggregation and peptide-related impurities. Is that something either of us could detect, and what would it look like if it happened?
  • What would a baseline and a follow-up look like, so that a change could be detected rather than assumed?

A clinician who answers "the human evidence here is unblinded, in a different population, for a different problem" is describing the literature accurately, not being dismissive.

Evidence by claim

Grades describe how strong the evidence is; the line under each grade describes what kind of studies it is. How we grade evidence.

Cognitive enhancement in healthy adults
Anecdotal reports only human observational

No published controlled trial has measured a cognitive outcome in healthy adults. Two placebo-controlled studies in healthy volunteers exist and both measured brain imaging rather than cognition: one reported a larger rostral, medial-frontal subcomponent of the resting default mode network in 14 volunteers given the peptide intranasally compared with 10 given placebo, and the other reported differences in resting functional connectivity between the right amygdala and right temporal cortex across 52 healthy participants receiving the peptide, Selank, or placebo in separate arms. Neither administered a memory, attention, or performance test as an endpoint. This is the claim most readers arrive with, and it is the claim with the least evidence behind it.

[11] [12]

Recovery after ischemic stroke
Anecdotal reports only human observational · review

The human efficacy literature is Russian-language and non-randomized. A 1997 study gave the peptide to 30 patients in the acute period of hemispheric ischemic stroke and compared them with 80 patients of matched severity and lesion location on conventional therapy, reporting some influence on the rate of restoration of the damaged neurological functions, in the form of increased regress of general cerebral and focal disorders, motor disorders especially; it is indexed as a controlled clinical trial and is not described as randomized or blinded. A 2018 study followed 110 patients after ischemic stroke, dividing them into early and late rehabilitation groups and subdividing each into subgroups that did and did not receive the peptide, and reported that the peptide raised and sustained plasma BDNF and that the peptide together with high BDNF levels accelerated and improved final Barthel index recovery; that report likewise does not describe randomization, blinding, or a placebo arm. A 2024 Russian-language review of this clinical literature concludes the oligopeptide is clinically effective in both the acute and the recovery period of ischemic stroke. Non-randomized comparisons without blinding or a placebo arm, reviewed within the same research community, do not support a grade above this one.

[8] [9] [10]

Induction of BDNF and trkB signalling in the brain
Animal studies only animal

This is the compound's best-characterized mechanism and all of it is in rats. Tritium-labelled peptide bound rat basal-forebrain membranes in a time-dependent, specific, reversible and calcium-dependent way, with a dissociation constant of 2.4 nanomolar, and intranasal application at 50 and 250 micrograms per kilogram raised BDNF protein in the basal forebrain within 3 hours but not in the cerebellum. A single 50 micrograms per kilogram application raised hippocampal BDNF protein 1.4-fold and trkB tyrosine phosphorylation 1.6-fold, with a distinct increase in conditioned avoidance reactions in the treated animals. Further in vivo work reported stimulated BDNF expression across different areas of the rat brain.

[1] [2] [3]

Neuroprotection in experimental cerebral ischemia
Animal studies only animal

In rats with permanent middle cerebral artery occlusion, genome-wide analysis found the peptide predominantly enhanced immune-system gene expression at 3 and 24 hours, with more than half of all altered genes belonging to the immune response, and altered 24 vascular-system genes at 3 hours and 12 at 24 hours. In a transient-occlusion model, the peptide was associated with upregulated active CREB in subcortical structures and downregulated MMP-9, c-Fos and active JNK. Both studies measure molecular intermediates in rats, not clinical outcomes in anyone.

[4] [5]

Effects on dopaminergic and serotonergic systems
Animal studies only animal

In rodents, tissue 5-hydroxyindoleacetic acid in the striatum rose by about 25% two hours after administration and extracellular 5-HIAA rose progressively to about 180% over one to four hours, while the peptide alone changed neither tissue nor extracellular dopamine or its metabolites. The authors described a positive modulatory effect on the striatal serotonergic system and an ability to increase amphetamine-elicited dopamine release and locomotion. No human neurochemical study of this compound has been published.

[6]

FOR RESEARCH PURPOSES ONLY

Typical protocol range in the research

  • Non-randomized clinical comparison in the acute period of hemispheric ischemic stroke, in which 30 patients received the peptide alongside combined intensive therapy and 80 patients of comparable stroke severity and lesion location received conventional therapy alone

    The authors identified 12 mg per day as the most effective daily dose in strokes of moderate severity and 18 mg per day in severe strokes, over treatment courses of 5 and 10 days [8]

  • Rehabilitation study of 110 patients after ischemic stroke, split into early and late rehabilitation groups and each group subdivided into subgroups that did and did not receive the peptide

    A standard regimen of 6000 mcg per day given as two courses of 10 days with a 20-day interval between them [9]

  • Rats given the peptide intranasally, with brain-derived neurotrophic factor protein in the basal forebrain measured 3 hours later

    50 and 250 micrograms per kilogram of body weight, single application [1]

  • Placebo-controlled resting-state functional MRI study in 24 healthy volunteers of mean age 44, imaged before and 5 and 20 minutes after a single intranasal administration

    A single intranasal administration of a 1% solution in 14 subjects, against placebo in 10 subjects; the report gives the concentration rather than a milligram figure [11]

Every human figure above comes from a Russian clinical or imaging study, and every one of them was generated in a population that is not the population reading this page. No published trial establishes a dose of Semax for cognitive enhancement in a healthy adult, because no published trial has tested that outcome at any dose. The fixed daily microgram figures that circulate in community discussion have no published trial behind them and are therefore not reported here.

Ranges are what published research reports, not a recommendation. PHL does not prescribe, and nothing here is personalized to you.

Side effects & safety signals

  • No published long-term human safety study

    Not established · The safety-directed published work on Semax is a cell-culture screen, in which the peptide at 0.1 and 10 micromolar significantly increased the survival of mouse embryonic stem cells under serum deprivation and had little effect on their differentiation into neuronal precursors. That is a cytotoxicity screen in cultured mouse cells, and it is not a human safety dataset. Nothing published follows anyone taking this compound over months or years.

    [7]

  • Tolerability is not reported in the human studies that exist

    Not systematically reported · Neither the 1997 acute-stroke comparison nor the 2018 rehabilitation study reports an adverse-event tally in its published abstract; both report efficacy endpoints only. An absence of reported harms in reports that did not set out to count them is not a finding of tolerability, and it should not be read as one.

    [8] [9]

  • Amplification of amphetamine's dopaminergic and behavioural effects in rodents

    Observed in rodents · Given alone, the peptide raised striatal 5-hydroxyindoleacetic acid and did not alter tissue or extracellular dopamine. Given 20 minutes before D-amphetamine, it dramatically increased amphetamine's effect on extracellular striatal dopamine and on locomotor activity. That is a rodent finding about a stimulant interaction, not a documented human one, but any concurrent stimulant, dopaminergic, or serotonergic medication is a reason to raise this compound with a clinician before considering anything.

    [6]

  • Broad modulation of immune-response gene expression

    Observed in rat focal cerebral ischemia · In a genome-wide transcriptional analysis of ischemic rat brain cortex, genes involved in the immune response made up more than half of all genes whose expression the peptide altered at 24 hours, with immunoglobulin and chemokine genes the most prominent groups. The authors read this as part of the mechanism of neuroprotection. What broad immune-gene modulation does in a person who is not having a stroke has not been studied, and an autoimmune or immunosuppressed history is a provider-discussion flag rather than a documented contraindication.

    [4]

Published lists are never exhaustive, so report anything unexpected to a licensed provider.

Storage, handling & reconstitution

Lyophilized storage
Lyophilized Semax is conventionally kept refrigerated at 2–8 °C and protected from light, with freezing used for longer holding. No published stability study addresses shelf life of the powder in a vial. The published pharmacology of the peptide concerns its behaviour after intranasal application in rats and its rapid clearance, which is a different question from how long a sealed vial holds its contents intact, and nothing in the cited literature speaks to the latter.
Reconstituted storage
Once in solution, peptides are conventionally refrigerated at 2–8 °C, protected from light, and treated as short-dated rather than indefinitely stable. No published study establishes a solution shelf life for Semax.
Reconstitution diluent
The conventional diluent for lyophilized research peptides, including Semax, is bacteriostatic water: sterile water preserved with 0.9% benzyl alcohol. Sterile water without a preservative is used where a preservative is contraindicated and is treated as single-use.
Reconstitution & handling
Conventional handling: sanitize the stopper before piercing it, add the diluent slowly down the inside wall of the vial rather than directly onto the powder, and let the powder dissolve on its own. Swirl gently if needed; never shake. A properly reconstituted solution is clear, and anything cloudy, discoloured, or carrying visible particulate is discarded. PHL does not publish volume or unit calculations, and does not describe how any preparation is administered, because those are dosing and administration decisions that belong with a licensed clinician.
Handling notes
Semax has no approved manufacturer in the United States, so there is no label, no assigned beyond-use date, and no lot-level stability testing standing behind any storage claim here. Treat all of the above as convention rather than specification, and note that nothing guarantees a vial holds the molecule its label names at the concentration claimed.

The how-to guides cover the conventions behind these fields, and what the published stability data does and does not establish: Storage, Reconstitution, Handling.

Questions for your provider

Bring this page to a licensed provider. A provider can order labs, review your medications and history, and tell you whether anything here is relevant to your situation. This page can't. Peptide Health Lab does not prescribe and does not sell peptides.

Want a structured starting point for that conversation? The Stack Builder turns your goals into a research-cited outline you can review together.

Citations

12 sources · every identifier checked against PubMed

Before you act on any of this

This page is educational only and is not medical advice. It does not diagnose, treat, or prescribe. Review it with a licensed provider before making any health decision. Peptide Health Lab does not sell peptides.

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