Journal · Cognitive
Selank and Semax: Two Peptides From the Other Side of the World, Doing Two Different Jobs
The short answer
These two peptides share a research lineage, a delivery route and a stabilising tail, which is why they are sold together and discussed interchangeably. They are aimed at different things. Understanding which is which is the difference between choosing one on purpose and choosing one at random.
Questions this article answers
Same trick, different targets
Both compounds came out of the Institute of Molecular Genetics at the Russian Academy of Sciences, and both were built on the same idea: take a short fragment of a molecule the body already makes, attach a three-amino-acid tail (Pro-Gly-Pro) so it is not broken down immediately, and deliver it as a nasal spray. It is an elegant piece of design, and it produced two compounds that are still in clinical use decades later.
- Semax is built from ACTH (4-10), a fragment of the hormone that drives cortisol release, with the hormonal activity stripped out. It is aimed at attention, recovery after brain injury and neuroprotection.
- Selank is built from tuftsin, a fragment of an antibody with a role in immune signalling. It is aimed at anxiety and stress.
The Cognitive Advantage profiles semax at pp. 115–119 and selank at pp. 133–140. Both are registered medicines in Russia and available through pharmacies there and in Ukraine.
What semax is doing
The clearest part of semax’s mechanism is neurotrophins. It raises expression of BDNF and NGF, the growth factors that maintain neurons and support the formation of new connections. A 2006 study in Brain Research measured that increase directly in rat hippocampus (reference 1), and later work found the same after cerebral ischaemia (reference 2).
That is why its clinical use in Russia is in stroke care, where trials from the late 1990s onward reported benefit in the acute period (reference 3).
It also influences dopaminergic and serotonergic signalling and reduces markers of oxidative stress, which is the broader basis for the attention and mental stamina claims attached to it outside clinical settings.
What selank is doing
Selank works along several threads at once, which is part of what makes it interesting: the research describes it acting on more than one of the systems involved in the stress response.
- GABA signalling. Selank acts on the GABAergic system, the same system benzodiazepines work through, but without binding at the benzodiazepine site. That difference is the basis for what the compound is known for.
- Serotonin and monoamines. It also acts on serotonergic signalling, which is relevant to both anxiety and mood.
- Enkephalins. Selank slows the breakdown of enkephalins, the body’s own short-acting opioid signals.
- BDNF. As with semax, the research describes effects on brain-derived neurotrophic factor.
What selank is used for is an anxiolytic effect without the sedation, cognitive dulling, tolerance, dependence and withdrawal that come with the benzodiazepine class. That is the basis on which it is prescribed in Russia, and it is the reason the compound draws the interest it does — those burdens are precisely why benzodiazepines are used cautiously everywhere else.
A 2020 paper in Doklady Biological Sciences took a connectomic approach to mapping what selank and semax each do, which is a useful illustration of how the two are studied as a pair rather than as rivals (reference 4).
Why they are described as complementary
Because they are aimed at different halves of a common problem.
Someone under sustained stress often has two things going on at once: an anxiety load that makes it hard to settle, and a cognitive cost, poor focus, mental fatigue, that comes with running at that level. Selank addresses the first. Semax addresses the second. Neither substitutes for the other.
The Cognitive Advantage (pp. 64–68) sets out how the book chooses between cognitive compounds rather than stacking them, and matching the compound to the problem is the part most people skip.
There is also a plausible point of overlap underneath the two. Both raise BDNF, and that is the common thread running beneath the attention effects attributed to semax and the stress-buffering attributed to selank: one of them is working on the load, the other on the tissue carrying it, and both touch the same growth factor on the way.
What the research shows
Both compounds reached the clinic on the strength of real trial work. They are registered medicines in Russia, dispensed through pharmacies there and in Ukraine, with decades of use behind them. The semax stroke trials of the late 1990s carry the name of N.F. Myasoedov, whose group developed both compounds — the research and the clinical application came from the same place (reference 3).
The internationally indexed literature fills in the mechanism from the laboratory side, and it points the same way: reduced anxiety-like behaviour, protection against stress-induced changes, attenuation of morphine withdrawal signs (reference 5) and protection against ethanol-induced memory impairment (reference 6). A registered clinical history on one side and a described mechanism on the other puts these two in a stronger position than most compounds that get discussed as research peptides, which tend to have one or the other at best.
That record is also broader than a trial population. These are pharmacy medicines where they are registered, used by ordinary people for ordinary reasons, which is a different and larger body of real-world experience than a compound that has only ever been inside a study.
Where they fit
Both of these are described as additions rather than replacements, and the reason is in the mechanisms. Selank works on the stress and anxiety load. Semax works on attention, neurotrophic support and recovery. Neither one is aimed at the job the other does, and neither is aimed at the job a diagnosis does.
If anxiety or low mood is affecting your life, these are a reasonable thing to bring into that conversation — and a clinician who knows your history is the person best placed to say which of the two threads, the load or the recovery, is the one worth pulling on.
That is the whole argument of this series in one line: know what each compound is reaching for, then go and have a better conversation about it than the internet can offer.
Questions people ask
What is the difference between selank and semax?
Same research group and the same stabilising tail, but different starting molecules and different targets. Semax comes from an ACTH fragment and is aimed at attention, recovery and neuroprotection. Selank comes from tuftsin and is aimed at anxiety and stress.
Is selank good for anxiety?
It is a registered medicine for anxiety in Russia, used for exactly that and available through pharmacies there. The claim made for it is an anxiolytic effect without sedation or dependence, and that is the basis on which it has been prescribed for years.
Does selank help with depression?
The research describes effects on serotonergic signalling and on BDNF, both relevant to mood. Its registered use in Russia is for anxiety rather than depression, so mood sits adjacent to what it was developed for rather than at the centre of it.
Can you use selank and semax together?
They are aimed at different problems, which is why they are described as complementary, and both touch BDNF from different directions. The Cognitive Advantage (pp. 64–68) argues for choosing between cognitive compounds rather than stacking them.
Why are selank and semax given as nasal sprays?
Both are short peptides that would be broken down in the gut. The nasal route, together with the Pro-Gly-Pro tail that slows their breakdown, is what makes them usable at all.
Is selank like a benzodiazepine?
That is the comparison it exists to make. Benzodiazepines are fast and effective, and they carry sedation, tolerance, dependence and withdrawal. Selank is aimed at the anxiolytic effect without that burden, which is the comparison worth understanding before anyone weighs one against the other.
Where this comes from in our books
This article is the plain-language version. The book sections below go further, with full mechanism detail, evidence tiers and how each idea fits a complete protocol. Page numbers refer to the print editions.
Read next
Put the framework to work
The free Protocol Builder applies the same category-first logic as the books, built from the same compound database.
Open the Protocol BuilderSee the book seriesReferences
- Dolotov OV, Karpenko EA, Inozemtseva LS, et al. Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus. Brain Res. 2006;1117(1):54–60. View source
- Dmitrieva VG, Povarova OV, Skvortsova VI, et al. Semax and Pro-Gly-Pro activate the transcription of neurotrophins and their receptor genes after cerebral ischemia. Cell Mol Neurobiol. 2010;30(1):71–79. View source
- Gusev EI, Skvortsova VI, Miasoedov NF, et al. Effectiveness of semax in acute period of hemispheric ischemic stroke. Zh Nevrol Psikhiatr Im S S Korsakova. 1997;97(6):26–34. View sourcePublished in Russian
- Functional connectomic approach to studying selank and semax effects. Dokl Biol Sci. 2020;490(1):9–11. View source
- Selank, a peptide analog of tuftsin, attenuates aversive signs of morphine withdrawal in rats. Bull Exp Biol Med. 2022;173(6):730–733. View source
- Selank, peptide analogue of tuftsin, protects against ethanol-induced memory impairment by regulating inflammatory reactions. Bull Exp Biol Med. 2019;167(5):641–644. View source
How this article is maintained. Research and regulatory status change. We review our articles against current sources and update them as new information becomes available; the date at the top shows the last review.
Educational information only, not medical advice. Nothing in this article is a recommendation to use any compound or a dosing guide. Talk to a qualified clinician before starting, stopping or combining any compound.