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Semax vs Selank

Last updated: October 3, 2026 · 5 min read · By the Grey Peptides Editorial Board

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Grey Peptides
Grey Peptides Editorial Board
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Key takeaways
  • Semax and selank are both Russian nasal peptides, approved as medicines only in Russia: semax for stroke and optic-nerve disease, selank for anxiety.
  • Their human evidence is small, mostly Russian and often open-label. Semax's centres on stroke recovery and BDNF; selank's on anxiety, compared with benzodiazepines.
  • Neither is approved in the US or EU, and neither has been tested as a nootropic in healthy people beyond brain-imaging studies.

Side by side

Semax Medium and selank Medium come from the same Russian research tradition and are sold together online, often as 'focus' and 'calm' versions of the same idea. They are different molecules with different approved uses in Russia 1. The table is read from our encyclopedia entries.

FieldSemaxSelank
Encyclopedia entrySemax Full entrySelank Full entry
Molecule classPeptidePeptide
CategoryCognitiveCognitive
FDA statusNot FDA ApprovedNot FDA Approved
Approved elsewhereRussiaRussia
Evidence gradeMediumMedium
Half-lifeNot measured in humansNot measured in humans
FormulaC37H51N9O10SC33H57N11O9
Molecular weight813.9 g/mol751.9 g/mol
WADA 2026Unsettled (S0 may apply)Unsettled (S0 may apply)
WADA 2027Unsettled (S0 may apply)Unsettled (S0 may apply)
In one lineA synthetic ACTH-derived heptapeptide approved in Russia for stroke rehabilitation and optic nerve disorders, with documented BDNF upregulation and broad nootropic activity.A Russian nasal anxiolytic built from the immune peptide tuftsin; its human evidence is small Russian trials that compare it with benzodiazepines, not placebo.
MechanismIn rats, a single dose raised hippocampal BDNF protein 1.4-fold and exon III BDNF mRNA threefold, with more trkB activation, and intranasal doses raised basal-forebrain BDNF within three hours; it binds specific sites there. It increased striatal serotonin turnover and strongly amplified amphetamine's dopamine and locomotor effects. In rat stroke models it shifts immune-response gene expression. How these findings translate to people is not established.Modulates GABA-A receptor sensitivity and enkephalin degradation without directly binding the benzodiazepine site. Upregulates expression of genes involved in inflammation, immune response, and neurogenesis. Has demonstrated anxiolytic activity comparable to diazepam in rodent models without the sedation, tolerance, or withdrawal associated with benzodiazepines, and without the serotonin-mediated side effects of SSRIs.
Sources in the entry1316
Study cards1114
Dosage pageDosage pageDosage page

Semax: a stroke and nerve drug

Semax is a synthetic fragment of the hormone ACTH, stabilised so it lasts longer, and given as nasal drops. In Russia it is approved as a medicine and used in stroke and optic-nerve disease 1. In rats a single nasal dose raised BDNF, a growth factor for nerve connections, in the hippocampus by up to 1.4 times and activated its receptor (animal evidence) 2.

Its human studies are about recovery. In 110 patients a few months after ischaemic stroke, two ten-day courses alongside rehabilitation raised plasma BDNF and were associated with better recovery measures (human study, not blinded) 3. An older study of 30 acute stroke patients reported 'some influence' on the speed of recovery against conventional treatment 4. In motor neuron disease, an open study found it did not change the course of the disease 5.

Selank: an anti-anxiety drug

Selank is a synthetic analogue of tuftsin, a short immune peptide, approved in Russia for generalised anxiety disorder and adjustment disorders 1. Its key human study compared it with the benzodiazepine medazepam in 62 patients with generalised anxiety or neurasthenia: anti-anxiety effects were similar, and selank also showed anti-fatigue, stimulant-like effects (randomised comparison, not placebo-controlled) 6. Added to phenazepam in 70 patients, it made phenazepam's benefit arrive sooner and reduced its side effects such as sedation and memory problems (human study) 7.

Laboratory work links selank to GABA signalling and to slowing the breakdown of enkephalins, the body's own calming peptides; patients with generalised anxiety had faster enkephalin breakdown, which selank reduced in their blood samples 8.

A 2020 Russian study gave 52 healthy people semax, selank or placebo and scanned their brains with functional MRI before and after. The groups differed in how the right amygdala, a region involved in fear and emotion, connected with parts of the temporal cortex, and the authors describe shared and distinct effects of the two peptides (human imaging study) 9. An earlier imaging study of semax alone found changes in the brain's default mode network in 24 healthy adults 10. These show both peptides change brain activity briefly; neither study measured memory, focus or anxiety as outcomes.

What neither has

Neither has a large, placebo-controlled, independently run trial. Most studies are Russian, many are open-label, and several abstracts lack key numbers. A 2021 review of GABA-acting drugs grouped selank with phenibut as poorly studied Russian drugs sold to US consumers as supplements (review) 11. Neither has been tested in healthy people as a cognitive enhancer, which is how both are mostly sold outside Russia. Our semax and selank evidence review goes deeper.

How the differences add up (as of October 3, 2026)

If the comparison is 'focus versus calm', the evidence roughly agrees on direction: semax's human studies concern brain recovery and BDNF, selank's concern anxiety. But both bodies of evidence are small, and neither is approved in the US, EU, UK, Canada or Australia 1. For athletes, neither is named on WADA's list; whether S0 applies depends on how Russia's approval is treated, so we record both as unsettled 1. Doses on this page are those in our entries' sources, not recommendations.

Frequently asked questions

What is the difference between semax and selank?

Semax is an ACTH fragment used in Russia for stroke and optic-nerve disease; selank is a tuftsin analogue approved in Russia for anxiety. Both are nasal peptides with small, mostly Russian human studies.

Is semax or selank better for anxiety?

Selank is the one studied for anxiety, where it matched medazepam in 62 patients. Semax's studies concern stroke recovery, not anxiety.

Are semax and selank legal in the US?

Neither is FDA-approved. Both are approved as medicines only in Russia.

Sources

  1. Grey Peptides dataset records for semax and selank (Russian approvals, FDA status, WADA status unsettled, studied doses as sourced on each entry); read October 3, 2026.
  2. Dolotov, O. V., et al. (2006). Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus. Brain Res, 1117(1), 54-60. PMID: 16996037
  3. Gusev, E. I., et al. (2018). [The efficacy of semax in the tretament of patients at different stages of ischemic stroke]. Zh Nevrol Psikhiatr Im S S Korsakova, 118(3. Vyp. 2), 61-68. PMID: 29798983
  4. Gusev, E. I., et al. (1997). [Effectiveness of semax in acute period of hemispheric ischemic stroke (a clinical and electrophysiological study)]. Zh Nevrol Psikhiatr Im S S Korsakova, 97(6), 26-34. PMID: 11517472
  5. Serdiuk, A. V., et al. (2007). [The study of chronic partial denervation and quality of life in patients with motor neuron disease treated with semax]. Zh Nevrol Psikhiatr Im S S Korsakova, 107(4), 29-39. PMID: 18379501
  6. Zozulia, A. A., et al. (2008). [Efficacy and possible mechanisms of action of a new peptide anxiolytic selank in the therapy of generalized anxiety disorders and neurasthenia]. Zh Nevrol Psikhiatr Im S S Korsakova, 108(4), 38-48. PMID: 18454096
  7. Medvedev, V. E., et al. (2015). [Optimization of the treatment of anxiety disorders with selank]. Zh Nevrol Psikhiatr Im S S Korsakova, 115(6), 33-40. PMID: 26356395
  8. Zozulya, A. A., et al. (2001). The inhibitory effect of Selank on enkephalin-degrading enzymes as a possible mechanism of its anxiolytic activity. Bull Exp Biol Med, 131(4), 315-7. PMID: 11550013
  9. Panikratova, Y. R., et al. (2020). Functional Connectomic Approach to Studying Selank and Semax Effects. Dokl Biol Sci, 490(1), 9-11. PMID: 32342318
  10. Lebedeva, I. S., et al. (2018). Effects of Semax on the Default Mode Network of the Brain. Bull Exp Biol Med, 165(5), 653-656. PMID: 30225715
  11. Doyno, C. R., et al. (2021). Sedative-Hypnotic Agents That Impact Gamma-Aminobutyric Acid Receptors: Focus on Flunitrazepam, Gamma-Hydroxybutyric Acid, Phenibut, and Selank. J Clin Pharmacol, 61 Suppl 2, S114-S128. PMID: 34396551

Educational information, not medical advice. Each dose in this guide names its source, an approved label or a published study. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose.

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