Semax with selank and dihexa
Semax with selank and dihexa (cognitive stack)
Written by Aaron CuhaReviewed Sep 2026
Also known as: Cognitive enhancement stack, Nootropic peptide trio
In plain English, from Aaron
This is how I would explain it to a friend. The evidence, with the numbers, is further down the page.
Three brain peptides sold as one stack. One is meant to sharpen you up, one to calm you down, one to build connections. Two of the three are registered medicines in Russia. The third rests on a paper that got retracted in 2025.
What people take it for
- Focus and mental sharpness.
- Less anxiety without feeling dopey.
- Memory and learning.
- Recovery after a brain injury.
What the trials actually showed
Nobody has tested the three together. Selank has the best record. Sixty two people with bad anxiety and burnout got selank or a standard anxiety drug. The anxiety relief was about the same in both. Selank also picked people up, which the paper calls a psychostimulant effect. Semax is registered and used in Russia, and the study on this page is in rats. One dose raised a brain growth protein 1.4 times in the rat hippocampus and the rats learned an avoidance task better. Both Russian records are domestic and nobody outside Russia has repeated them. Now dihexa. The paper that explained how it works got an expression of concern in 2021 and was retracted by the journal in 2025. Some of its authors worked for a company developing the drug. A retracted paper is not proof the drug does nothing. It does mean the main published reason for putting dihexa in a brain stack has been pulled.
What people report
Reports, not trial results
The good
- Sharper focus and easier speech within the first hour, credited to the semax.
- Less anxiety without feeling flat, credited to the selank. That matches what the trial found.
The bad
- Irritability or feeling overstimulated, especially at higher amounts.
- Headache.
- Most people say they notice nothing from the dihexa part.
- One part is meant to speed you up and one to slow you down, and the seller picked the balance for you.
- Semax and selank are used as nose drops in Russia. Stacks sold to inject change the route the human use came from.
Where these come from: Nootropic and peptide forums plus seller pages. People talking, about their own thinking, which is the easiest thing in the world to fool.
My bottom line
When the paper that explains how a drug works gets retracted, treat the drug as unknown, not promising. Two thirds of this stack has something behind it. One third does not any more.
An opinion, not a finding. I am a coach, not a doctor.
Overview
Three nootropic peptides sold as one cognitive stack. Two are registered medicines in Russia with small domestic trials; the third rests on a paper that was retracted in 2025 after an expression of concern in 2021. The combination has never been tested, and no vial size is standard across sellers.
The pitch is one activating peptide, one calming peptide and one synaptogenic peptide, covering focus, anxiety and long-term plasticity. Each third of that pitch has a different evidentiary problem.
Semax is a heptapeptide analogue of the ACTH 4-10 fragment, registered and used clinically in Russia. Its mechanistic work is largely rodent: a single application at 50 micrograms per kilogram produced a maximal 1.4-fold rise in hippocampal BDNF protein, a 1.6-fold rise in trkB tyrosine phosphorylation, and three-fold and two-fold rises in exon III BDNF and trkB mRNA in rat hippocampus, with treated animals showing more conditioned avoidance reactions. Rats, one dose, hippocampal tissue.
Selank is a tuftsin analogue also registered in Russia. It has a randomised comparative trial: 62 patients with generalised anxiety disorder and neurasthenia, selank in 30 and medazepam in 32, assessed on the Hamilton, Zung and CGI scales. The anxiolytic effects of the two drugs were similar, and selank also had antiasthenic and psychostimulant effects. That is a real clinical trial, in a Russian journal, against an active comparator rather than placebo.
Dihexa is the problem. The paper that established its mechanism, showing it binds hepatocyte growth factor and induces c-Met phosphorylation and hippocampal spinogenesis and synaptogenesis, carried an expression of concern in 2021 and was retracted in 2025. Some of the authors were affiliated with a company developing the compound, disclosed in the paper. A retracted mechanism paper is not the same as a disproved compound, but it means the central published basis for including dihexa in a cognitive stack has been withdrawn by the journal.
No vial size or capsule strength is canonical across sellers for this trio, so this page does not state a per-dose amount. What is structural regardless of split is that one component is sold as stimulating and one as calming, so the blend puts opposing intents in one draw at a ratio the buyer did not choose, and the third component's inclusion rests on withdrawn evidence.
Mechanism of action
Semax is described as modulating BDNF and trkB expression in rodent hippocampus and as having neuroprotective effects in the Russian clinical literature. Selank is a tuftsin analogue with anxiolytic activity linked to enkephalin metabolism. Dihexa was characterised as an angiotensin IV derived peptide acting through hepatocyte growth factor and c-Met, in a paper that has since been retracted. No published work describes the three together.
Human evidence
One component has a small comparative clinical trial, one has rodent mechanism work and a Russian clinical tradition, and one has a retracted mechanism paper. The stack has nothing.
- The stack: no published study, no registered trial.
- Selank: 62 patients with generalised anxiety disorder and neurasthenia, anxiolytic effects similar to medazepam, with additional antiasthenic and psychostimulant effects reported.
- Semax: registered and used clinically in Russia; the mechanistic work cited here is in rats.
- Dihexa: no human trial. The key mechanism paper was retracted in 2025 after an expression of concern in 2021.
What this does not tell you: The Russian clinical literature for both registered peptides is domestic, mostly in Russian, and has not been replicated by independent groups outside Russia. That is a limitation on confidence rather than a reason to dismiss it, and it is the honest description of where this evidence sits.
What it has been measured to do
Measured in people
Goals Semax with selank and dihexa has been measured for in a human being, most people first. Counts come from the study lines on this page and deliberately undercount.
- Mood and anxiety62 people · 1 study
What people using it report
Uncontrolled and self-selected, so it cannot show that anything works. It is still the best guide on this page to what people actually do with Semax with selank and dihexa, what they expect, and what goes wrong. The full account, including the negative reports, is below.
34 of the 36 indexed goals have no study of any kind behind Semax with selank and dihexa
No trial, no animal work, no cell work on this page reports a result for these. That is an absence of evidence rather than evidence of absence, but it does mean anything you have been told about Semax with selank and dihexa and one of these did not come from a study cited here.
Reading the research record
The retraction is the fact that should change a decision. When the paper that established a compound's mechanism is withdrawn by the journal, after an expression of concern that stood for four years, the rational response is to treat the compound as uncharacterised rather than as promising. Dihexa continues to be sold and stacked on the strength of a literature that now has a hole in the middle of it.
The second issue is the shape of the product. Selling an activating peptide and a calming peptide in a fixed ratio means the vendor has decided the balance between stimulation and sedation for every buyer. There is no titration available, and no way to find out which component is responsible for whatever happens.
The third issue is route. Semax and selank are used in Russian practice as nasal drops. Stacks sold for injection take two peptides out of the delivery route in which their clinical use developed.
The evidence, charted
Fig. 1a · evidence scale
62people, across 1 human study cited here
- 2008 · Zhurnal Nevrologii i Psikhiatrii imeni S.S. Korsakova62100%
The whole total is one study of 62. Counts are the enrollment each human citation on this page states, which includes observational cohorts where nobody was given the compound. Studies still recruiting are excluded, and only studies cited on this page are counted.
Fig. 1b · evidence mix
1 of 3 citations here is human work, the rest are not.
- Human · given to people133%
- Animal · given to animals267%
Counted from the citation list on this page, typed as this page types it. It understates any literature larger than the sources we cite, and a review counts once however many studies it covers.
Fig. 2 · evidence over time
Evidence spans 3 distinct years, 2006 to 2014, counted from the citation list on this page. The newest citation on file is from 2014, more than five years ago; the published record may have gone quiet.
Fig. 3 · legal status at a glance
US
Not approved
UK
Not approved
AU
Not approved
CA
Not approved
Not approved in any of the four jurisdictions shown. A jurisdiction's classification is a regulatory fact, not a verdict on the science; see Legal status below for the full text and any notes.
Fig. 5 · molecular identity
- Modality
- Blend
- Molecular weight
- Not on file
- Half-life
- Stated in words, not a number
- Sequence length
- None on file
see the exact wording below
Half-life as stated on file: Not defined for the stack, and no pharmacokinetic study of the combination exists. The two Russian peptides are typically dosed intranasally rather than injected.
No amino acid sequence is on file for Semax with selank and dihexa, which is expected: a blend is not built from residues.
Fig. 6 · what is in the vial
No mass split can be drawn for this blend
Sellers do not publish a consistent vial size for Semax with selank and dihexa, so the share of each component is not knowable from the outside. Splitting the bar evenly would invent the number this page exists to question.
Component list from the product labels we hold. Amounts are label mass, never a dose.
Key studies & citations
- Animal2006
Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus
A single application of semax at 50 micrograms per kilogram produced a maximal 1.4-fold increase in BDNF protein and a 1.6-fold increase in trkB tyrosine phosphorylation, with three-fold and two-fold increases in exon III BDNF and trkB mRNA, in rat hippocampus. Treated animals showed a distinct increase in conditioned avoidance reactions. Rats, single dose.
Brain Research - Human2008
[Efficacy and possible mechanisms of action of a new peptide anxiolytic selank in the therapy of generalized anxiety disorders and neurasthenia]
62 patients with generalised anxiety disorder and neurasthenia, 30 on selank and 32 on medazepam, assessed with the Hamilton, Zung and CGI scales alongside serum enkephalin activity. The anxiolytic effects of the two drugs were similar, and selank also showed antiasthenic and psychostimulant effects. An active comparator trial in a Russian journal, with no Western replication.
Zhurnal Nevrologii i Psikhiatrii imeni S.S. Korsakova - Animal2014
The procognitive and synaptogenic effects of angiotensin IV-derived peptides are dependent on activation of the hepatocyte growth factor/c-met system
The paper establishing dihexa's claimed mechanism, reporting that it binds hepatocyte growth factor, induces c-Met phosphorylation and produces hippocampal spinogenesis and synaptogenesis. PubMed flags it as a retracted publication: an expression of concern was published in 2021 and the retraction followed in 2025. Several authors were affiliated with a company developing the compound, disclosed in the paper. It is cited here because its withdrawal is the relevant fact about dihexa, not because it supports the compound.
Journal of Pharmacology and Experimental Therapeutics
What users report
Self-reported experiences, not evidence. Nothing below was measured under controlled conditions, and reports like these cannot separate a real effect from placebo, from the training or diet change that accompanied it, or from what the product actually contained. They are here because knowing what people describe, including what goes wrong, is worth reading alongside the studies.
- Sharper focus and verbal fluency within the first hour, attributed to the semax.
- Reduced anxiety without sedation, attributed to the selank, which matches what the comparative trial reported.
- Irritability or overstimulation, particularly at higher amounts.
- Headache.
- No noticeable effect from the dihexa component, which is the most common specific criticism of these stacks.
- Difficulty telling the three apart, since they are taken together.
Sources: Nootropic forums including r/nootropics and r/peptides, and vendor pages. Uncontrolled self-reports in a domain where expectation effects on subjective cognition are large and where nobody is measuring anything.
Frequently asked questions
Was a paper on one of these retracted?
Yes. The paper establishing dihexa's hepatocyte growth factor mechanism carried an expression of concern in 2021 and was retracted by the journal in 2025. That is the central published basis for including dihexa in a cognitive stack.
Does selank have a real trial?
It has a comparative trial in 62 patients with generalised anxiety disorder and neurasthenia, where its anxiolytic effect was similar to medazepam. It is a Russian domestic trial with no independent Western replication.
What is the semax evidence?
Russian clinical registration plus rodent mechanism work. The study cited here gave rats 50 micrograms per kilogram and measured hippocampal BDNF and trkB, with a 1.4-fold rise in BDNF protein.
Is combining a stimulating and a calming peptide sensible?
It is at least a decision, and the vendor made it. A fixed ratio means you cannot raise one and lower the other, and you cannot tell which of the three is producing any effect you notice.
Should these be injected?
Semax and selank are used as nasal drops in the clinical practice where their evidence comes from. A stack sold for injection changes the route away from the one the human use developed in.