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Comparison

N-Acetyl Semax Amidate vs Selank

Both are nootropic & neuro, so the meaningful differences are in kinetics, evidence and regulatory status.

On published evidence alone, Selank is the better documented of the two (preliminary human). That is a statement about the state of the literature, not a recommendation.

N-Acetyl Semax Amidate Selank
Class Nootropic & neuro Nootropic & neuro
Evidence Anecdotal only Preliminary human
Human trials None published ~6
Half-life ~1-2 hours ~30 minutes (intranasal)
Reported range 100-300 mcg 250-750 mcg
Frequency 1-2x daily intranasal 1-3x daily intranasal
Routes Intranasal, Subcutaneous Intranasal, Subcutaneous
FDA approved No No
Research use only Yes Yes
Banned in sport No No
Studied for Cognitive enhancement research, Focus and motivation Generalised anxiety research, Stress resilience, Cognitive support
Reported side effects Nasal irritation, Overstimulation, Headache, Irritability Nasal irritation, Transient drowsiness, Headache

N-Acetyl Semax Amidate

N-acetyl semax amidate adds an acetyl group to the N-terminus and an amide to the C-terminus of Semax. Both modifications are standard medicinal-chemistry approaches to slowing exopeptidase degradation, and they plausibly extend duration and improve membrane permeability. The widely repeated claim that it is several times more potent than Semax traces to vendor marketing rather than to any published comparative study, and the page should say so.

Selank

Selank is a heptapeptide built from the immunomodulatory tetrapeptide tuftsin with a proline-glycine-proline extension added for stability. It appears to act by modulating the expression and metabolism of enkephalins and by influencing GABAergic and serotonergic signalling, producing anxiolysis without the sedation, motor impairment or withdrawal associated with benzodiazepines. It is registered as a medicine in Russia; Western trial evidence is limited.

N-Acetyl Semax Amidate vs Selank: common questions

What is the difference between N-Acetyl Semax Amidate and Selank?

Both are nootropic & neuro. N-Acetyl Semax Amidate: An acetylated and amidated Semax variant marketed as more potent and longer lasting. The potency claims are not from published human work. Selank: A synthetic tuftsin analog developed in Russia as an anxiolytic without sedation or dependence.

Which has stronger evidence, N-Acetyl Semax Amidate or Selank?

Selank has the stronger evidence base (preliminary human, about 6 human studies) compared with N-Acetyl Semax Amidate (anecdotal only).

Are N-Acetyl Semax Amidate and Selank FDA approved?

Neither is FDA approved for any indication.

References

Regulatory and primary sources

  1. PubChem compound record (CID 172638603) ↗ · structure, identifiers, synonyms
  2. FDA: Unapproved drugs and "research use only" products ↗ · regulatory status of non-approved products
  3. PubChem compound record (CID 11765600) ↗ · structure, identifiers, synonyms
  4. CAS Registry Number 129954-34-3 ↗ · chemical identity

Published literature

  1. Rahman OF, Lee SJ, Seeds WA. Therapeutic Peptides in Orthopaedics: Applications, Challenges, and Future Directions.J Am Acad Orthop Surg Glob Res Rev 2026.PubMed 41490200 · doi:10.5435/JAAOSGlobal-D-25-00236
  2. Tarasov VV, Kudryashov NV, Chubarev VN, et al.. Pharmacological Aspects of Neuro-Immune Interactions.Curr Pharm Des 2018.PubMed 28875850 · doi:10.2174/1381612823666170829135115
  3. Sudakov KV. [Evolution of the stress concept].Vestn Ross Akad Med Nauk 2008.PubMed 19140465
  4. Gusev EI, Martynov MY, Kostenko EV, et al.. [The efficacy of semax in the tretament of patients at different stages of ischemic stroke].Zh Nevrol Psikhiatr Im S S Korsakova 2018.PubMed 29798983 · doi:10.17116/jnevro20181183261-68
  5. Vyunova TV, Medvedeva EV, Andreeva LA, et al.. [POSSIBLE ROLE OF TRANSTHYRETIN IN THE BIOLOGICAL MECHANISM OF THE REGULATORY PEPTIDE NEUROPROTECTION.].Mol Gen Mikrobiol Virusol 2016.PubMed 30383932
  6. Giri S, Chandra P. Modulation of neuropathological pathways by bioactive peptides and proteins/polypeptides: Targeting oxidative stress in neurodegenerative diseases.Neuropeptides 2025.PubMed 41004910 · doi:10.1016/j.npep.2025.102563
  7. Umnov RS, Lin'kova NS, Khavinson VKh. [Neuroprotective effects of peptides bioregulators in people of various age].Adv Gerontol 2013.PubMed 24738258
  8. Liapina LA, Pastorova VE, Obergan TIu, et al.. [Comparison of anticoagulant effects of regulatory proline-containing oligopeptides. Specificity of glyprolines, semax, and selank and potential of their practical application].Izv Akad Nauk Ser Biol 2006.PubMed 16634437
  9. Siebert A, Gensicka-Kowalewska M, Cholewinski G, et al.. Tuftsin - Properties and Analogs.Curr Med Chem 2017.PubMed 28745220 · doi:10.2174/0929867324666170725140826
  10. Sano Y, Sakamoto A, Oi Y, et al.. Anaesthesia and circulating blood volume.Eur J Anaesthesiol 2005.PubMed 15892402 · doi:10.1017/s0265021505000438
  11. Medvedev VE, Tereshchenko ON, Kost NV, et al.. [Optimization of the treatment of anxiety disorders with selank].Zh Nevrol Psikhiatr Im S S Korsakova 2015.PubMed 26356395 · doi:10.17116/jnevro20151156133-40
  12. Medvedev VE, Tereshchenko ON, Israelian AIu, et al.. [A comparison of the anxiolytic effect and tolerability of selank and phenazepam in the treatment of anxiety disorders].Zh Nevrol Psikhiatr Im S S Korsakova 2014.PubMed 25176261
  13. Alevizos B, Alevizos E, Leonardou A, et al.. Low dosage lithium augmentation in venlafaxine resistant depression: an open-label study.Psychiatriki 2012.PubMed 22796912
  14. Zozulia AA, Neznamov GG, Siuniakov TS, et al.. [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 2008.PubMed 18454096

Literature retrieved from PubMed on October 16, 2026, favouring human studies and reviews. Numbered markers in the text show which paper supports which statement; uncited entries are background reading.

Read this first This page compares published reference data. It is not medical advice and not a recommendation to use either compound. Several compounds documented on this site are not approved for human use.