Semax vs Selank: Which Nootropic Peptide Fits Your Goal?

Semax vs Selank is a choice between two peptides from the same Moscow institute. They share a three-amino-acid tail and sit side by side in Russian pharmacies. After that, they part ways.

Podcasts sell them as a matched pair: one to sharpen you, one to steady you. The trial record is thinner and stranger than that. Almost every human study comes from Russia, most carry the developers’ names, and ClinicalTrials.gov lists none at all. This page gives you three things the clinic blogs skip:

• Every human trial in one table, with the doses the studies used and an evidence grade.
• A goal-by-goal decision matrix for anxiety, focus, stress, sleep, depression, ADHD and stroke.
• The Nootroholic COA check: five products from four vendors, priced per mg and tested for identity by mass. One combination vial came with a certificate for a different peptide altogether.

What Is Semax?

Heptapeptide synthesized at the Russian Academy of Sciences’ Institute of Molecular Genetics.

The design started with a seven-residue fragment of ACTH, a hormone that activates cortisol production in the body.

The makers kept the first four residues and swapped the last three. The peptide is a stronger painkiller than ACTH (4-10) itself. A single nasal dose lasted 20 to 24 hours in animals and people. The adrenal glands aren’t pushed to make cortisol.

It is manufactured by Peptogen in two strengths:

• 0.1% drops (1 mg/mL): for memory and thinking disorders caused by poor blood flow to the brain, recovery after head injury or surgery, optic nerve atrophy and, on some label versions, “minimal brain dysfunction” in children.
• 1% drops (10 mg/mL) for the acute phase of moderate or severe ischaemic stroke, administered along with standard care.

Semax is on Russia’s official Vital and Essential Drugs List. 60 to 70% of a nasal dose is absorbed. Semax crosses the blood-brain barrier.

N-acetyl Semax

N-acetyl Semax amidate is not Russian medicine. N-acetyl Semax amidate, Ac-Semax-NH2, is a research-market variant with an acetyl group on the front end. The changes are described as extra potency. Only laboratory chemistry has been peer-reviewed.

Studies show that acetylation alters how the peptide binds to copper and zinc. No studies on human comparison with plain Semax. Its molecular mass also differs from plain Semax, which matters when reading a COA (see the buying section).

What Is Selank?

A synthetic heptapeptide derived from tuftsin, a four-amino-acid fragment of IgG. It has the same Pro-Gly-Pro tail as Semax. It is registered as a nasal anxiolytic in Russia.

Selank has anti-anxiety and antidepressant effects without sedative properties.

Additionally, it has also been studied for its cognitive-enhancing properties. It may also regulate the immune system, potentially benefitting immune system-related diseases.

In Russia, the following groups of conditions are included: anxiety states, panic attacks, neurasthenia (diminished ability to endure and become irritated), mood swings, sleep disorders, stress and adjustment disorders.

Selank’s pitch is an anxiolytic without sedation.

NA-Selank

Another research market innovation featuring the same end caps as N-acetyl semax. It’s not a registered medicine. There have been no human or animal studies published as of September 2026.

Semax vs Selank: Key Differences

The front half of the molecule is the main difference.

Semax’s front half is a hormone fragment linked to learning and brain repair.

Selank’s is an immune fragment linked to relaxation. Both have the same Pro-Gly-Pro tail. Semax research centres on BDNF and dopamine; Selank research centres on GABA and enkephalin.

How Semax works: BDNF and dopamine

One nasal dose of Semax raised hippocampal BDNF protein 1.4-fold and TrkB phosphorylation 1.6-fold in rats. The amount of BDNF messenger RNA increased trippled. The expression of one type of BDNF mRNA was also increased threefold.

BDNF helps neurons form and sustain connections. It’s for this reason Semax is called a memory peptide.

Experimental strokes on rats have shown that Semax primarily switches on immune and blood-vessel genes. This is the key to its protective effects.

The other half is dopamine. In mice, Semax intensifies amphetamine-induced dopamine release in the striatum. The FDA says this is a typical response to abuse drugs, like cocaine.

How Selank works: GABA and enkephalins

The connection of GABA to Selank appears to be indirect. Within an hour, one dose altered 45 of 84 nerve-signaling genes in rats, with the pattern following GABA. The researchers say that Selank indirectly affects the GABA system.

The opioid system plays a role as well. In mice, Selank’s calming effect was diminished by Naloxone.

The body’s own opioids are called enkephalins. In an anxiety trial conducted in 2008 Selank extended the half-life of enkephalins, which have rapid degradation.

What Marketing intersection leaves out

BDNF vs GABA split is mostly a sales pitch. The peptides blocked the enzyme that breaks down enkephalins in a 2001 study. Semax was the strongest of the two, having enzyme activity at 10 µM against Selank’s 20 µM.

The only human study to test both in one protocol found shared and distinct effects. A 2020 fMRI study of 52 healthy adults found that each peptide changed the connection between the right amygdala and the right temporal cortex.

Which is better for Anxiety, Focus or Depression?

For anxiety, Selank. Most successful trials were made with comparisons to benzodiazepines. The evidence suggests that Semax can help with focus and memory, but these are based on brain scans and the developers’ own reports – and not outcome trials. A controlled human trial for depression and/or ADHD is not listed in PubMed.

Selank for anxiety

A 2008 randomized trial with 62 people with generalized anxiety disorder or neurasthenia found Selank (30 patients) was as effective as benzodiazepine medazepam (32). It also helps with fatigue. The effects lasted a week after the last dose, similar to those of phenazepam. None of the trials used a placebo, so expectation effects cannot be excluded. They all came from Moscow groups including Selank’s developers.

Semax for focus and ADHD

The case for Semax as a focus drug for healthy people rests on the developers’ 1997 review and a 2018 study of 24 volunteers. In that study, one dose of 1% Semax enlarged the brain’s default mode network on fMRI within 20 minutes. A changed brain scan isn’t better work. The ADHD claim is traced to a 2006 hypothesis paper arguing that Semax’s dopamine and BDNF effects might suit ADHD. We found no controlled ADHD trials.

Semax or Selank for depression

In a 2024 rat study of chronic stress, Semax reversed anhedonia (loss of pleasure) and restored hippocampal BDNF. Selank reduced depression-like behaviour in a 2008 rat study The FDA’s review found reports of Semax use in children with depression or tics, but no controlled adult trial exists for either peptide.

Can You Take Semax and Selank Together?

No study has given Semax and Selank together to people or animals. The pairing comes from forums and vendors, not trials. The closest data is from a 2020 fMRI study that gave 52 healthy adults Semax, Selank or a placebo on their own. Any claim about the combination is an exaggeration.

Three findings shape how researchers think about pairing:

• The peptides overlap. Both carry Pro-Gly-Pro, and both slow enkephalin breakdown. Semax is stronger at this. So the combination isn’t a clean “one for each pathway” design.
• The labels pull in opposite directions. Semax’s Russian label excludes people with anxiety disorders, the group Selank is registered for. The stress-plus-focus rationale for pairing them runs into Semax’s own exclusion.
• The only combination of Selank with a benzodiazepine. In a 2015 randomised trial of 70 patients, adding Selank to phenazepam brought a faster response and fewer side effects, such as memory problems and sedation.

Pre-mixed products add a practical problem. In our COA check, one Selank/Semax vial had no certificate of its own. The only Selank nasal spray we found was blended with DSIP. The more peptides shared in a vial, the more difficult it is to prove what’s inside.

What the studies show?

The human evidence for Semax and Selank is 11 studies of more than 770 people, all Russian and most co-authored by the developers. Stroke and anxiety have been studied in controlled trials. Healthy-volunteer data is limited to brain scans. No trial is registered on ClinicalTrials.gov, and no Western group has replicated any results.

What it adds up to

Three weaknesses run through the record. First, none of the clinical-outcome trials was placebo-controlled and blinded. Second, the same research network, often including Semax and Selank’s co-developer Nikolay Myasoedov, wrote most of the papers. Third, most appear only in Russian-language journals with short English abstracts. The FDA reached a blunt verdict on Semax in 2026: the studies were small, some relevant outcomes weren’t reported, and the evidence did not show effectiveness for its nominated uses.

That isn’t proof that the peptides don’t work. It means the evidence has never been tested the way Western regulators demand.

Nasal Spray vs Injection: How Semax and Selank Reach the Brain

Every human study of Semax and Selank used nasal drops. The FDA found no published human study of injected Semax. Russian labelling reports that 60 to 70% of a nasal Semax dose is absorbed and that Semax crosses the blood-brain barrier. In rats, the nose delivered Selank to the brain better than injection into the abdomen or a vein, or delivery by stomach tube.

Route can change what a peptide does, not just how much arrives. In a 2016 mouse study, injected Selank increased GABA-receptor binding in the frontal cortex by 38%. The same peptide given through the nose left GABA receptors unchanged and raised NMDA-receptor binding in the hippocampus by 23% instead.

Both peptides are broken down fast in blood. Selank splits into smaller fragments, and one of them, Gly-Pro, reproduced many of Selank’s effects on immune genes in mice. Research vendors mostly ship freeze-dried powder in vials, a format no published human study has used. The FDA has flagged a specific worry about injected and sprayed peptides of uncertain purity: impurities and clumped peptide can provoke immune reactions.

Side Effects and Safety: What the Labels and the FDA Found

The side effects reported for Semax and Selank are mild: nasal irritation for Semax, and allergic reactions and a bitter taste for Selank. The larger issue is what hasn’t been studied. There are no human pharmacokinetic data for Semax, no long-term safety studies for either peptide, and no independent test of abuse potential.

Safety signals worth knowing

• Seizure-like EEG activity. In the 1999 study of 73 patients with brain damage after oxygen loss, some showed paroxysmal (seizure-like) EEG activity after Semax. The authors advised monitoring brain activity during the first dose. Semax’s label excludes people with a history of seizures.
• Bleeding. Semax acted as an anticoagulant and antithrombotic in rats. The FDA noted this could raise bleeding risk in vulnerable people or alongside blood-thinning drugs.
• Dopamine and abuse potential. Semax boosted amphetamine-driven dopamine release in mice. No one has run the standard abuse-liability studies.
• One US adverse-event report. The FDA’s FAERS database holds one report linked to Semax. A consumer had eye pain and burning after using 0.1% drops bought online in 2024, was hospitalised, and still had symptoms a year later.
• Selank and GABA drugs. A 2021 review in the Journal of Clinical Pharmacology grouped Selank with phenibut as “poorly studied Russian drugs with GABAergic mechanisms”. The authors noted that both are sold to US consumers as dietary supplements and called for abuse-potential testing before public access.

Who the labels and trials excluded

Russian labelling excludes pregnancy and breastfeeding for both peptides and under-18s for Selank and 1% Semax. Semax’s label also excludes acute psychosis, anxiety disorders and a history of seizures. The Semax label states that no studies have been done in pregnancy. Every trial in the table above ran for weeks, not years.

Legal Status in the US, UK, EU and Russia

Semax and Selank are registered medicines only in Russia. Neither is approved by the FDA, the EMA or the UK’s MHRA. In the US, Semax moved closer to legal pharmacy compounding in July 2026, but no final rule exists. Selank isn’t on the list that compounding pharmacies may use.

• Semax, US: The FDA placed Semax in Category 2, its list of substances with significant safety concerns for compounding. On 23–24 July 2026, the Pharmacy Compounding Advisory Committee voted 8–5, with one abstention, to recommend adding Semax to the 503A bulks list. FDA scientists had recommended against it, citing safety, effectiveness and characterisation gaps. The vote isn’t binding, and rulemaking may take until 2027 or longer.
• Selank, US: Selank acetate came off Category 2 in September 2024 after its nominator withdrew. It still isn’t on the bulks list, so pharmacies can’t compound it. It wasn’t on the July 2026 agenda.
• UK and EU: No marketing authorisation for either peptide.
• Russia: Both are registered medicines made by Peptogen. Semax is on the national essential-drugs list.

Buying Semax or Selank: Nootroholic COA Check

Only two of the five products we checked came with a certificate that proves identity by mass. An HPLC test shows that the powder is mostly one substance, not which one. Proving what’s in the vial takes mass spectrometry, which weighs the molecule, or a match against a reference standard. The masses below are the numbers to look for:

We reviewed the public certificates for every Semax and Selank product sold by four US vendors on 25 September 2026:

Ascension is the only vendor whose Semax and Selank certificates weigh the molecule, and both measured more peptide than the label claims. Elite Edge’s Semax is the cheapest per mg by a wide margin, but a certificate with an unknown batch can’t be matched to any vial. NextGen’s spray has the fullest safety panel of anything we checked. Its identity row names only DSIP, though, so the certificate can’t tell you how much Selank you’re getting.

The N-acetyl naming trap

Limitless Biotech sells “N-Acetyl Semax” and “N-Acetyl Semax Amidate” as two separate products. Both pages list the same sequence (Ac-Met-Glu-His-Phe-Pro-Gly-Pro-NH2), the same formula, the same 854.97 g/mol weight and the same CAS number. Either the first product is really the amidate, or its specification is wrong. Prices sit behind a “research access” login. A mass-spec certificate settles it: 854.37 Da means amidate, 855.36 means the free acid, and 813.35 means plain Semax sold under a premium name.

Our best peptide vendors list explains how we vet sellers, and our guide on how to read a peptide COA walks through each line of a certificate.

Adamax and Other Analogues

Adamax is a research-market analogue sold as a modified Semax, and it has no peer-reviewed literature. A PubMed search in September 2026 returned no study of it. N-acetyl Semax and NA-Selank are in the same position: popular on vendor sites and absent from the literature. Our Adamax peptide guide covers what vendors claim and what can be checked.

For other brain-focused peptides, see our Dihexa guide, our page on Pinealon and our list of 72 peptides.

Semax vs Selank FAQ

Sources