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How Selank Works: Mechanism and Pharmacology

How Selank works: its target and mechanism as the sources state them, how long it acts, and what is still unknown.

Medical review pendingTuftsin analogUpdated
Class
Tuftsin analog
FDA status
Not approved
research chemical
Routes studied
intranasal; intranasal and intraperitoneal; intraperitoneal
Half-life
[pending]
by route, with source

How long it acts

No published half-life found for Selank (PubMed search, 11 Oct 2026)

Full detail, including drug-testing windows, is on the Selank half-life page.

What selank is and what it acts on

Selank is a heptapeptide, Thr-Lys-Pro-Arg-Pro-Gly-Pro, and in plasma it inhibited the enzymatic hydrolysis of enkephalin with an IC50 of 15 microM, more potently than bacitracin and puromycin.[5]

A rodent paper describes selank as a synthetic derivative of the endogenous peptide tuftsin and says its neurobiochemical effects include activation of brain monoaminergic systems and dopamine turnover.[6]

In patients with generalized anxiety disorder and neurasthenia the half-life of leu-enkephalin was lower, and treatment with selank increased this parameter.[7]

What is seen in animals and cells

In BALB/c mice, 100 micrograms/kg of selank produced an anxiolytic effect and raised the half-life of plasma leu-enkephalin, with no effect in C57Bl/6 mice.[8]

In rats, one selank injection activated serotonin metabolism in the hypothalamus and caudal brain stem for 30 minutes to 2 hours.[9]

In ethanol-exposed rats, selank prevented the ethanol-induced increase in BDNF content in the hippocampus and frontal cortex.[10]

A rat anxiety paper states that the anxiolytic effect of selank is comparable to classical benzodiazepines and that their mechanisms may be similar; this is the authors' framing of animal work.[11]

In cell culture, selank completely suppressed IL-6 gene expression in blood cells from patients with depression but not from healthy controls; this is in vitro data.[12]

Why timing and duration come up

In the phenazepam comparison, the anxiolytic effect of selank lasted for a week after the last dose.[13]

In rats with poor learning ability, selank effects were apparent after the first dose on training day 1 and grew with repeated dosing.[14]

The labelling study found selank is rapidly broken down, with the pentapeptide TKPRP, tripeptide TKP and dipeptides RP and GP as the major products.[15]

What is unknown

Drugs@FDA returns no match for selank, so there is no label mechanism or pharmacodynamics section.[16]

A PubMed search for selank with half-life or pharmacokinetic terms, run on 2 Oct 2026, returned 4 records; no half-life or plasma concentration value for selank was found in the cached sources.

Calculated from query selank[tiab] AND (half-life[tiab] OR pharmacokinetic*[tiab]); date 2026-10-02; count 4. Formula: count as recorded in evidence/selank.json searches

Related peptides

Selank vs SemaxACTH(4-10) analog

Common questions

How long does Selank act in the body?

We found no published half-life for Selank (PubMed search, 11 Oct 2026), so how long it acts is unknown.

How does selank work?

The authors of the plasma enzyme study suggest selank works in anxiety by inhibiting enkephalin hydrolysis; this is a proposed mechanism.[5]

Does selank work immediately?

Only rat data speak to onset: effects on learning were apparent after the first dose on training day 1; no human onset study is cached.[14]

More on Selank

DosageDoses used in published studies, with the source for each.CalculatorVial, water and dose to syringe units.Side effectsWhat labels and studies report, and what is unknown.ResultsStudy outcomes and when they were measured.BenefitsClaimed benefits next to what published studies measured.Nasal sprayStudies that gave Selank as nasal spray, and what is approved.

Sources

  1. 1PubMed search: selank[tiab] (68 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026
  2. 2PubMed search: selank[tiab] AND (half-life[tiab] OR pharmacokinetic*[tiab]) (4 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026
  3. 3PubMed search: (selank[tiab] OR semax[tiab]) AND (randomized[tiab] OR patients[tiab] OR clinical[tiab]) (48 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026
  4. 4PubMed search: selank[tiab] AND (adverse[tiab] OR "side effect*"[tiab] OR safety[tiab] OR tolerab*[tiab] OR toxicity[tiab] OR "case report"[pt]) (7 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 11 Oct 2026
  5. 5The inhibitory effect of Selank on enkephalin-degrading enzymes as a possible mechanism of its anxiolytic activity.Bulletin of experimental biology and medicine · 2001PMID 11550013Accessed 2 Oct 2026
  6. 6[Effects of heptapeptide selank on genetically-based and situation-provoked symptoms of depression in behavior in WAG/Rij and Wistar rats, and in BALB/c mice].Zhurnal vysshei nervnoi deiatelnosti imeni I P Pavlova · 2008PMID 18661785Accessed 2 Oct 2026
  7. 7[Efficacy and possible mechanisms of action of a new peptide anxiolytic selank in the therapy of generalized anxiety disorders and neurasthenia].Zhurnal nevrologii i psikhiatrii imeni S.S. Korsakova · 2008PMID 18454096Accessed 2 Oct 2026
  8. 8Effects of Selank on behavioral reactions and activities of plasma enkephalin-degrading enzymes in mice with different phenotypes of emotional and stress reactions.Bulletin of experimental biology and medicine · 2002PMID 12432865Accessed 2 Oct 2026
  9. 9[Experimental optimization of learning and memory processes by selank].Eksperimental'naia i klinicheskaia farmakologiia · 2010PMID 20919548Accessed 2 Oct 2026
  10. 10Selank, Peptide Analogue of Tuftsin, Protects Against Ethanol-Induced Memory Impairment by Regulating of BDNF Content in the Hippocampus and Prefrontal Cortex in Rats.Bulletin of experimental biology and medicine · 2019PMID 31625062Accessed 2 Oct 2026
  11. 11Peptide Selank Enhances the Effect of Diazepam in Reducing Anxiety in Unpredictable Chronic Mild Stress Conditions in Rats.Behavioural neurology · 2017PMID 28280289Accessed 2 Oct 2026
  12. 12[Immunomodulatory effects of selank in patients with anxiety-asthenic disorders].Zhurnal nevrologii i psikhiatrii imeni S.S. Korsakova · 2008PMID 18577961Accessed 2 Oct 2026
  13. 13[A comparison of the anxiolytic effect and tolerability of selank and phenazepam in the treatment of anxiety disorders].Zhurnal nevrologii i psikhiatrii imeni S.S. Korsakova · 2014PMID 25176261Accessed 2 Oct 2026
  14. 14The optimizing action of the synthetic peptide Selank on a conditioned active avoidance reflex in rats.Neuroscience and behavioral physiology · 2003PMID 14552529Accessed 2 Oct 2026
  15. 15[Evenly tritium-labeled peptides and their in vivo and in vitro biodegradation].Bioorganicheskaia khimiia · 2006PMID 16637290Accessed 2 Oct 2026
  16. 16Drugs@FDA (openFDA) search: active ingredient "selank"U.S. Food and Drug Administration · 2026api.fda.govAccessed 2 Oct 2026

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