Selank and semax together: seven studies name both, none gave both to a person, and at one measured point they do the same thing

What it is. Two Russian peptides taken together, often in one nasal spray sold by vendors: semax, from a fragment of ACTH, and selank, from a fragment of the immune peptide tuftsin.

Nobody has given both to the same person in a study. Seven papers name both, which is more than most combinations on this site can claim, and none of them is a study of the pair.

The stacking case assumes they do different things. At the one point where both have been measured in the same experiment, they did the same thing: a 2001 study found both inhibit the same enzyme in human serum.

They also share a tail. Both end in the tripeptide Pro-Gly-Pro, which has its own activity, so taking both means more of that fragment.

What is sold in the West is not what was studied. The acetylated and amidated versions have no trial evidence of their own, individually or together.

Seven indexed papers name both compounds. None administered both to the same person. The closest is a 2020 brain-imaging study that gave semax to one group, selank to another and placebo to a third, which is a comparison rather than a combination.

This is worth stating precisely because the stack is sold as a single product. A vendor selling both in one bottle is making a claim the literature does not contain.

Read the second row again. It is the only experiment in which both compounds were measured in the same system on the same endpoint, and it found them acting on the same target.

A 2001 study reported a dose-dependent effect of synthetic heptapeptides Semax (Met-Glu-His-Phe-Pro-Gly-Pro) and Selank (Thr-Lys-Pro-Arg-Pro-Gly-Pro) on the enkephalin-degrading enzymes in human serum. Both slow the breakdown of enkephalins, the body's own opioid-like signalling peptides.

Notice the sequences the authors print. The last three residues are identical: Pro-Gly-Pro. That shared tail is not inert, and a 2014 rat study examined its own effect on brain gene expression precisely because it is the C-terminal fragment of both drugs.

So two of the things these compounds are known to do, inhibiting the same enzyme and delivering the same active tripeptide, are things they do identically. Stacking them increases the dose of those two actions rather than adding a new one.

That is not an argument that the combination is useless. The brain-imaging study did find effects that were not identical, so there is some separation. It is an argument that the intuition behind the stack, one calms and one sharpens and they work on different systems, is only partly right and has never been tested in a person.

Most of the search volume here is for the product rather than the idea: a single nasal spray containing both, sold by vendors and ranking on the first page for this query.

One bottle fixes two things nobody has studied. The ratio between the compounds is set by whoever mixed it. The schedule becomes one schedule, although the two were studied separately and the trials that exist used different regimens.

There is a third problem specific to this pair. The products sold in the West are usually N-acetyl semax amidate and N-acetyl selank amidate, modified molecules with no trial evidence at all. A combined spray of two untested analogues is two steps removed from the Russian trial literature people cite for it.

No published dose exists for the pair. Each compound's studied doses are on its own record with the study that produced them: semax and selank. Both are given intranasally in most of their studies and by injection in some, and the semax trials report percentage solutions rather than milligram figures.

The stacking schedules that circulate come from clinics and vendors. This site's boundary is that a dose appears when a study or a label gave it, so they are not reproduced.

Both are described as well tolerated in their own small Russian trials, and selank's literature specifically claims anxiolytic effects without sedation or dependence. Those statements describe the registered Russian products given singly.

For the pair there is nothing. The one toxicity study naming both is a screen in mouse embryonic stem cells, in which selank altered how many cells became GABA-producing neurons, a finding about developing cells in a dish. And the forensic analysis in this ledger exists because these peptides turn up in seized products, which is its own comment on what is being sold.

Discussed for: anxiety with focus, brain fog, and general cognitive support, mostly in nootropic communities and by clinics selling peptide therapy.

Studied in: for semax, people recovering from stroke, optic-nerve disease and motor neurone disease; for selank, people with diagnosed anxiety disorders. Separately, and in Russia.

The unresolved questions are whether the pair does anything the single compounds do not, whether the shared enzyme inhibition and shared tail make the combination redundant at those points, and whether any of it applies to the acetylated forms people actually buy. None has been studied.

The question of which one to choose is answered on the comparison page.

1. Assuming complementary action. Both inhibit the same enzyme in the one experiment that measured them together.
2. Ignoring the shared tail. Both end in Pro-Gly-Pro, which is itself active, so stacking doubles it.
3. Citing the Russian trials for a combined spray. Those trials used the registered products, singly.
4. Treating the imaging study as evidence for the stack. It gave each compound to a different group.
5. Taking a vendor's ratio as a protocol. Nobody studied it.
6. Forgetting the forms. The acetylated versions sold in the West have no trial evidence individually, let alone together.