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Semax

Semax is a synthetic heptapeptide (Met-Glu-His-Phe-Pro-Gly-Pro), an analogue of the ACTH(4-10) fragment of adrenocorticotropic hormone, but reported to be devoid of the corticotropic/hormonal activity of ACTH. It is used (registered and marketed in Russia and some former-Soviet states, largely as an intranasal solution) as a "neuroprotective/nootropic" agent for ischemic stroke, transient ischemic attacks, chronic cerebrovascular insufficiency, and off-label for cognition/attention. The human evidence base is weak: nearly all clinical data come from small, non-blinded, single-country (Russian) trials of low methodological quality, and a 2026 orthopedic peptide review explicitly notes the absence of rigorous clinical trials. There is essentially no adequate controlled human safety data, no Western regulatory approval, and no robust data for the "cognitive enhancement" use that most non-patients pursue. Product sold to consumers is typically unregulated research-grade material of unverified identity/purity. Because it is a peptide with minimal systematic toxicology in humans, its true adverse-effect profile is unknown rather than proven safe. Anyone using it should do so under medical supervision with baseline bloodwork, and should stop and seek care for any neuropsychiatric, allergic, or unexpected symptoms.

Clinical readoutPeptide · neuropeptide-nootropic
Hepatic strainLow
CardiovascularNone
HPTA suppressionNone
Half-life
Very short for th…
Route
Intranasal solution/dro…
Evidence
C
Active
Reported dosing is once…
1·t½2·t½3·t½4·t½5·t½
Illustrative single-compartment washout · each mark = one half-life · t½ ≈ Very short for the parent peptide. Robust human PK data are lacking; rodent tracer studies show rapid enzymatic degradation on the order of minutes, with the parent heptapeptide converted largely to the tripeptide Pro-Gly-Pro. Claimed prolonged clinical effect (hours to ~24h) reflects downstream neurotrophic signaling, not sustained plasma peptide levels.
Pharmacology

Mechanism of action

Semax is a synthetic analogue of the N-terminal ACTH(4-10) melanocortin fragment, stabilized against enzymatic breakdown by a C-terminal Pro-Gly-Pro motif. Unlike ACTH, it is reported to lack corticotropic (adrenal steroidogenic/hormonal) activity. Its principal proposed mechanism is upregulation of neurotrophic signaling: preclinical work shows intranasal Semax binds specific calcium-dependent sites in rat basal forebrain and rapidly increases brain-derived neurotrophic factor (BDNF) protein, a modulator of synaptic plasticity. A small human stroke trial reported increased plasma BDNF during treatment. Additional proposed/preclinical mechanisms include modulation of the central dopaminergic system and augmentation of psychostimulant-induced dopamine release, anti-inflammatory/immunomodulatory shifts (increased IL-10, IL-4, IL-13; decreased pro-inflammatory mediators), and transcriptomic downregulation of immune-associated genes in brain. The active degradation product Pro-Gly-Pro is itself biologically active and more stable, and may contribute to effects. Overall the mechanism is characterized mainly in rodents; human mechanistic data are limited to BDNF/cytokine correlations in stroke patients.
Kinetics

Pharmacokinetics

Half-life

Very short for the parent peptide. Robust human PK data are lacking; rodent tracer studies show rapid enzymatic degradation on the order of minutes, with the parent heptapeptide converted largely to the tripeptide Pro-Gly-Pro. Claimed prolonged clinical effect (hours to ~24h) reflects downstream neurotrophic signaling, not sustained plasma peptide levels.

Active duration

Reported dosing is once to a few times daily (intranasal); Russian clinical courses typically run 5-10 days, sometimes repeated. Pharmacodynamic (e.g., BDNF) effects are proposed to outlast measurable peptide. No validated human active-duration data.

Route

Intranasal solution/drops is the standard human route (chosen for nose-to-brain delivery bypassing extensive peptidase degradation); parenteral routes have been used in preclinical/experimental settings. Not orally bioavailable as intact peptide.

Metabolism & clearance

Metabolized by tissue and plasma peptidases (aminopeptidase/proline-specific enzymes) to smaller fragments, predominantly Pro-Gly-Pro. Rapid systemic clearance; renal handling of small peptide fragments assumed but not well characterized in humans. Presented here for washout/monitoring context only, not for evading any test.

For monitoring and washout planning, not drug-test evasion.

Reported effects

Physiological & performance effects

  • Reported in small Russian stroke/cerebrovascular trials to modestly accelerate recovery of neurological deficit, improve motor performance (British MRC scale) and functional independence (Barthel index) when added to standard care
  • Associated with increased plasma BDNF during stroke rehabilitation in one clinical trial
  • Claimed nootropic effects on attention, learning and memory - demonstrated mainly in rodents; human cognitive-enhancement data in healthy adults are essentially absent/anecdotal
  • Preclinical anti-inflammatory / immunomodulatory effects (increased anti-inflammatory cytokines, reduced pro-inflammatory markers)
  • Preclinical neuroprotective effects in models of cerebral ischemia, optic nerve injury and spinal cord injury
  • Proposed antidepressant/anxiolytic-like and dopaminergic-modulating effects - preclinical only
  • Subjectively reported by users as mild stimulation/focus, but not supported by controlled human data
Safety

Adverse effects by system

Cardiovascular

No adequate human safety data. A rat myocardial infarction study found Semax did not impair cardiac function (and showed ultrastructural protection). No systematic human cardiovascular adverse-event data exist; unknown rather than proven safe.

Hepatic

No human hepatotoxicity data and no signal identified; as a rapidly degraded peptide, clinically significant liver injury is not an established concern, but this reflects absence of study, not demonstrated safety.

Endocrine / HPTA

Semax is reported to be devoid of the corticotropic/hormonal activity of parent ACTH, so adrenal/HPA stimulation is not an expected effect; however, no human endocrine safety studies (cortisol, HPA, HPTA axis) have characterized this. Treat endocrine effects as unstudied.

Reproductive

No human data. No pregnancy, lactation, fertility or teratogenicity studies adequate to establish safety; should be considered contraindicated in pregnancy/breastfeeding by default.

Neuropsychiatric

No systematic human neuropsychiatric safety data. Given proposed dopaminergic/CNS activity, effects on mood, anxiety, sleep and agitation are biologically plausible but uncharacterized; unexpected psychiatric symptoms should prompt discontinuation.

Renal

No human renal safety data. Small peptide fragments are presumed renally handled; no nephrotoxicity signal reported, but not systematically studied.

Hematologic

No human hematologic safety data. Preclinical work notes immunomodulatory/cytokine shifts, but effects on blood counts or coagulation in humans are unstudied.

Dermatologic

No specific human data beyond the possibility of local nasal mucosal irritation with intranasal use and general risk of hypersensitivity/allergic reaction to a peptide product. Injectable misuse adds injection-site and sterility risks.

Recovery

HPTA suppression & recovery

Suppression: Not expected to suppress the HPTA/HPA axis (no established suppression); unstudied in humans

Semax is reported to lack the hormonal/corticotropic activity of parent ACTH, so it is not anticipated to act on gonadal or adrenal steroidogenesis, and there is no evidence it suppresses testosterone or the HPTA axis. However, no human endocrine data confirm this. This monograph does not recommend any post-cycle or SERM protocol; Semax is not an anabolic/androgenic agent and single-SERM recovery frameworks are not applicable. Anyone with endocrine concerns, abnormal labs, or symptoms of hormonal disturbance should consult a qualified endocrinologist rather than self-manage.

Bloodwork & vitals

Monitoring

Recommended labs & checks
Baseline and periodic CBCComprehensive metabolic panel including liver enzymes (ALT/AST) and renal function (creatinine/eGFR)Blood pressure and heart rate monitoringConsider baseline endocrine panel (morning cortisol, testosterone/LH/FSH) if any hormonal symptoms arise - interpreted by a clinician/endocrinologistClinical neuropsychiatric check-in (mood, sleep, anxiety)

Cadence: Establish a baseline before starting, then reassess symptoms during any short course; obtain labs if a course is prolonged/repeated or if symptoms develop. Because human safety data are lacking, err toward more clinician contact, not less.

Warning signs — seek care
  • Signs of allergic reaction (rash, swelling, difficulty breathing) - stop immediately and seek emergency care
  • New or worsening headache, blood-pressure changes, palpitations or chest pain
  • New anxiety, agitation, mood change, insomnia or other neuropsychiatric symptoms
  • Persistent nasal irritation, bleeding, or local reaction with intranasal use
  • Any focal neurological symptoms (weakness, speech/vision change) - treat as possible stroke and call emergency services
Do not use if

Contraindications

  • Pregnancy and breastfeeding (no adequate safety data - default contraindicated)
  • Known hypersensitivity/allergy to the peptide or excipients
  • Use of unverified, non-pharmaceutical/research-grade product of unknown identity or purity
  • Children/adolescents except under specialist medical supervision
  • Acute uncontrolled psychiatric illness (proposed CNS/dopaminergic activity, uncharacterized safety) - caution/medical oversight
  • Self-treatment of acute stroke symptoms in place of emergency care (stroke is a medical emergency requiring 911/hospital evaluation)
  • Any use as a substitute for evidence-based medical treatment
Combinations

Interaction profile

  • ContraindicatedWith DNP: Additive cardiovascular strain

Check a specific combination in the interaction checker.

Harm reduction

Reducing harm & when to stop

  • Recognize the evidence gap: efficacy claims rest on small, non-blinded, mostly Russian trials and rodent studies; there is no rigorous controlled human safety data and no data supporting cognitive enhancement in healthy adults. Do not assume 'well tolerated in trials' means proven safe.
  • Never use Semax to self-treat acute stroke, TIA, or any focal neurological symptoms - these are emergencies; call emergency services.
  • If using at all, do so under a clinician's supervision with baseline bloodwork (CBC, liver and kidney function, blood pressure) and periodic reassessment.
  • Consumer/research-grade peptide is unregulated and may be misidentified, underdosed, overdosed, or contaminated; injectable misuse adds infection and sterility risks. This monograph does not advise on sourcing.
  • Start only after discussing with a healthcare provider, especially if pregnant/breastfeeding (avoid), a child/adolescent, or if you have a psychiatric or cardiovascular condition.
  • Stop and seek care for: allergic reaction, new neuropsychiatric symptoms (anxiety, agitation, mood change, insomnia), palpitations/chest pain, blood-pressure changes, persistent nasal irritation/bleeding, or any focal neurological symptoms.
  • Do not combine with stimulants or other CNS-active drugs without clinician review; preclinical data suggest Semax can potentiate dopaminergic/psychostimulant effects.
  • This is informational harm-reduction content, not medical advice or an endorsement of use.
Evidence

Citations (14)

Every clinical claim above is tied to a primary source. Overall evidence grade C — graded to the best available evidence for its core claims.

  1. 01

    Semax is a synthetic heptapeptide analogue of the ACTH(4-10) fragment (Met-Glu-His-Phe-Pro-Gly-Pro) with nootropic and neuroprotective activity

    PreclinicalDOI 10.1016/j.npep.2020.102114 ↗

  2. 02

    Semax is an analogue of ACTH(4-10) but is completely devoid of hormonal (corticotropic) activity; it augments psychostimulant effects on central dopamine release and stimulates central BDNF

    ReviewDOI 10.1016/j.mehy.2006.07.017 ↗

  3. 03

    Intranasal Semax binds specific calcium-dependent sites in rat basal forebrain and rapidly increases BDNF protein, a proposed mechanism for its cognitive/neurotrophic effects

    PreclinicalSemax, an analogue of adrenocorticotropin (4-10), binds specifically and increases levels of brain-derived neurotrophic factor protein in rat basal forebrainDOI 10.1111/j.1471-4159.2006.03658.x ↗

  4. 04

    In post-ischemic-stroke patients, Semax increased plasma BDNF levels and was associated with faster functional recovery and improved motor performance/Barthel index (small non-blinded clinical trial)

    Case seriesPMID 29798983 ↗

  5. 05

    In acute hemispheric ischemic stroke, Semax added to intensive therapy was associated with faster regression of neurological/motor deficit; daily doses of 12 mg (moderate) and 18 mg (severe) over 5-10 day courses were reported

    Cohort[Effectiveness of semax in acute period of hemispheric ischemic stroke (a clinical and electrophysiological study)]PMID 11517472 ↗

  6. 06

    Semax was studied for immunobiochemical/anti-inflammatory mechanisms in acute ischemic stroke, shifting cytokine balance toward anti-inflammatory mediators (IL-10) over pro-inflammatory factors (IL-8, CRP)

    Case series[Investigation of mechanisms of neuro-protective effect of semax in acute period of ischemic stroke]PMID 10358912 ↗

  7. 07

    In 187 patients with cerebrovascular insufficiency, Semax was reported to be well tolerated with a low percentage of side effects, including in older patients

    CohortPMID 15792140 ↗

  8. 08

    Standard clinical dosing in stroke rehabilitation used courses of 6000 mcg/day (two 10-day courses with a 20-day interval)

    Case series[The efficacy of semax in the treatment of patients at different stages of ischemic stroke]DOI 10.17116/jnevro20181183261-68 ↗

  9. 09

    After intranasal administration in rats, Semax rapidly penetrates the brain but undergoes rapid enzymatic degradation, with the tripeptide Pro-Gly-Pro predominating among metabolites

    PreclinicalDOI 10.1134/s1068162006010055 ↗

  10. 10

    Intranasally administered Semax penetrates the brain and eye tissue in rats (PK/neuroprotection substantiation for optic-nerve disease)

    PreclinicalPMID 15678666 ↗

  11. 11

    In a rat acute myocardial infarction model, Semax did not impair cardiac function and prevented ischemia-induced ultrastructural cardiomyocyte changes

    Preclinical[Protective effect of peptide semax the rat heart in acute myocardial infarction]PMID 16967870 ↗

  12. 12

    Intranasal ACTH(4-7)-Pro-Gly-Pro (Semax) increased anti-inflammatory cytokine (IL-4, IL-10, IL-13) expression in a rat spinal cord injury model

    PreclinicalDOI 10.12688/f1000research.127413.2 ↗

  13. 13

    Semax alters brain frontal-cortex transcriptome, predominantly downregulating immune-system-associated genes, and its effects under normal physiology must be considered when assessing risk

    PreclinicalDOI 10.1134/S0006297924090104 ↗

  14. 14

    Semax (and related neuroactive peptides) show promise preclinically via BDNF pathways but there is a current lack of clinical trials

    ReviewDOI 10.5435/JAAOSGlobal-D-25-00236 ↗

Last reviewed 2026-07-06 · Verified against PubMed · Educational, not medical advice