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How Semax Works: Mechanism and Pharmacology

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

Medical review pendingACTH(4-10) analogUpdated
Class
ACTH(4-10) analog
FDA status
Not approved
Off Category 2, 15 Apr 2026
Routes studied
intranasal; intranasal and intraperitoneal; intraperitoneal
Half-life
[pending]
by route, with source

How long it acts

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

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

What semax is and what it is built from

An optic-nerve paper describes semax as a synthetic analog of adrenocorticotropic hormone 4-10 with a pronounced nootropic effect.[5]

Replacing the three C-terminal residues of ACTH4-10 with Pro-Gly-Pro raised analgesic potency after peripheral injection in rodents; this is animal data.[6]

A review states the heptapeptide is an analogue of ACTH fragment 4-10 but completely devoid of any hormonal activity.[7]

Pathways the sources point to

In rats with a toxin lesion of the dopaminergic system, the protective activity of semax may be associated with a modulating effect on dopamine pathways and with neurotrophic action.[8]

A review of animal work says semax can augment psychostimulant effects on central dopamine release and stimulates central BDNF synthesis.[7]

After ischemic stroke, semax was reported to increase plasma BDNF levels that stayed high through the study period, in a human trial without a described blinding method.[9]

A recent rat study names semax as ACTH(4-7)-Pro-Gly-Pro, a noncorticotropic analog, and found chronic treatment attenuated a stress-induced fall in hippocampal BDNF.[10]

What happens to it after intranasal dosing

After intranasal dosing in rats, 0.093% of the radioactivity per gram was found in brain 2 minutes later, and 80% of it belonged to semax with the rest as metabolites.[11]

The labelled peptide undergoes rapid enzymatic degradation, with the tripeptide Pro-Gly-Pro prevailing among its products in rat samples.[11]

What is unknown

Drugs@FDA returns no match for semax, so there is no label with mechanism of action or pharmacodynamics sections.[12]

A PubMed search for semax with half-life or pharmacokinetic terms, run on 2 Oct 2026, returned 4 records, and the cached pharmacokinetic work is a rat tritium-labelling study.

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

Related peptides

Semax vs SelankTuftsin analog

Common questions

How long does Semax act in the body?

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

How does semax work?

The animal work links semax to modulation of dopamine pathways and neurotrophic action; this is a hypothesis from rats, not a human mechanism study.[8]

Does semax work?

The human abstracts cached here are small and none describes blinding; the PubMed count behind this is 208 semax records in total, mostly rodent work.

Calculated from query semax[tiab]; date 2026-10-02; count 208. Formula: count as recorded in evidence/semax.json searches

More on Semax

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 Semax as nasal spray, and what is approved.

Sources

  1. 1PubMed search: semax[tiab] (208 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 2 Oct 2026
  2. 2PubMed search: semax[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: semax[tiab] AND (adverse[tiab] OR "side effect*"[tiab] OR safety[tiab] OR tolerab*[tiab] OR toxicity[tiab] OR "case report"[pt]) (17 results)PubMed · 2026pubmed.ncbi.nlm.nih.govAccessed 11 Oct 2026
  5. 5[Evaluation of therapeutic effect of new Russian drug semax in optic nerve disease].Vestnik oftalmologii · 2000PMID 10741256Accessed 2 Oct 2026
  6. 6Comparative study of analgesic potency of ACTH4-10 fragment and its analog semax.Bulletin of experimental biology and medicine · 2007PMID 18018999Accessed 2 Oct 2026
  7. 7Semax, an analogue of adrenocorticotropin (4-10), is a potential agent for the treatment of attention-deficit hyperactivity disorder and Rett syndrome.Medical hypotheses · 2007PMID 16996699Accessed 2 Oct 2026
  8. 8The neuroprotective effects of Semax in conditions of MPTP-induced lesions of the brain dopaminergic system.Neuroscience and behavioral physiology · 2004PMID 15341218Accessed 2 Oct 2026
  9. 9[The efficacy of semax in the tretament of patients at different stages of ischemic stroke].Zhurnal nevrologii i psikhiatrii imeni S.S. Korsakova · 2018PMID 29798983Accessed 2 Oct 2026
  10. 10Antidepressant-like and antistress effects of the ACTH(4-10) synthetic analogs Semax and Melanotan II on male rats in a model of chronic unpredictable stress.European journal of pharmacology · 2024PMID 39442746Accessed 2 Oct 2026
  11. 11[Kinetics of Semax penetration into the brain and blood of rats after its intranasal administration].Bioorganicheskaia khimiia · 2006PMID 16523722Accessed 2 Oct 2026
  12. 12Drugs@FDA (openFDA) search: active ingredient "semax"U.S. Food and Drug Administration · 2026api.fda.govAccessed 2 Oct 2026

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