Semax

Semax is a synthetic heptapeptide (Met-Glu-His-Phe-Pro-Gly-Pro) derived from the adrenocorticotropic hormone fragment ACTH(4-10). Unlike the parent hormone, it does not stimulate adrenal steroidogenesis.

The primary documented molecular mechanism is upregulation of BDNF (brain-derived neurotrophic factor) and its high-affinity receptor TrkB in the hippocampus. A single intranasal dose of 50 mcg/kg in rats produced a 1.4-fold increase in hippocampal BDNF protein, a 1.6-fold increase in TrkB tyrosine phosphorylation, a 3-fold increase in BDNF exon III mRNA, and a 2-fold increase in TrkB mRNA (Dolotov et al., Brain Research, 2006, PMID 16996037). TrkB activation drives downstream MAPK/ERK and PI3K/Akt cascades supporting synaptic plasticity and long-term potentiation.

Semax also modulates monoaminergic systems. In rodent striatum, it elevated the serotonin metabolite 5-HIAA by approximately 25% at two hours and extracellular serotonin metabolite levels to 180% within four hours. Semax alone did not alter baseline dopamine concentrations but markedly potentiated amphetamine-induced dopamine release, suggesting a facilitatory rather than direct dopaminergic action (Eremin et al., 2006, PMID 16362768).

Additional proposed mechanisms include inhibition of enkephalin-degrading enzymes (reported IC50 approximately 10 µM) and partial modulation of melanocortin receptors MC4 and MC5. In ischemia-reperfusion models, Semax suppresses phospho-JNK (greater than 1.5-fold reduction), reduces MMP-9 and c-Fos expression, and upregulates phospho-CREB, indicating concurrent anti-inflammatory and pro-survival activity at the transcriptional level.

Most human evidence for Semax originates from Russian-language clinical publications and has not been independently replicated in large Western trials.

The most cited controlled study enrolled 110 stroke patients (43 men, 67 women; mean age 58 years) divided into early and late rehabilitation subgroups. Semax was administered intranasally as two 10-day courses at 6,000 mcg/day with a 20-day washout between courses. Treatment raised plasma BDNF levels throughout the study period and was associated with improved Barthel functional independence scores and faster motor performance recovery relative to standard care (PMID 29798983, Russian neurology journal, 2018).

A resting-state fMRI study (Lebedeva et al., Bulletin of Experimental Biology and Medicine, 2018; PMID 30225715) assigned 24 healthy middle-aged volunteers (11 men, 13 women; mean age 43.9 years) to intranasal 1% Semax (n=14) or placebo (n=10). Imaging at 5 and 20 minutes post-dose detected a greater volume of the default mode network rostral subcomponent in the medial frontal cortex in the Semax group, a region associated with episodic memory and social cognition. The sample size is small and the functional significance of the observed change was not established.

For optic nerve disease, Russian studies including one trial of 36 glaucoma patients (24 receiving Semax plus standard IOP-lowering therapy; 12 receiving standard therapy alone) reported electrophysiological improvements in the treatment arm, forming part of the basis for the Russian-approved indication.

Animal studies using rat middle cerebral artery occlusion models document upregulation of Bdnf, Ngf, TrkA, TrkC, and Nt-3 mRNA at 3-72 hours post-ischemia (PMC11498467), suppression of approximately 394 differentially expressed genes at 24 hours post-injury, and reduction of inflammatory mediators including Mmp9 and Ccl6 (PMC7350263; PMC8226508). These preclinical findings are mechanistically consistent with the human stroke data but do not themselves constitute clinical evidence.

The overall human evidence base is small, concentrated in Russian publications, lacks Cochrane-level systematic review, and has not received regulatory evaluation outside Russia and Ukraine.

Typical dosage: 300-600 mcg (daily).

Semax is not FDA-approved and has no Western prescribing label. The protocols below reflect Russian-approved clinical indications and community-reported use.

In Russia, Semax is available in two intranasal formulations. The 0.1% solution is indicated for cognitive disorders, mental fatigue, and optic nerve disease:

• Mental fatigue or prophylactic cognitive use: 400-900 mcg/day divided into 2-3 administrations per day, for 3-5 days • Optic nerve disorders: 600-900 mcg/day in 2-3 administrations, for 7-10 days • Amnestic or cognitive impairment: 200-2,000 mcg per administration up to 4 times daily (total 800-8,000 mcg/day), for 10-14 days

The 1% solution is indicated for acute ischemic stroke and is administered under medical supervision:

• Moderate stroke: 2,000-3,000 mcg per administration, 3-4 times daily (6,000-12,000 mcg total/day), for 10 days • Severe stroke: 3,000-4,000 mcg per administration, 4-6 times daily (up to 20,000 mcg/day), for 10 days; cycling is used in practice (two 10-day courses separated by a 20-day washout)

Subcutaneous injectable Semax is reported in research and community settings at 500-1,000 mcg/day, but this route has not been validated in human clinical trials and carries no established safety profile.

This content is for educational and informational purposes only and does not constitute medical advice. Semax is not approved for medical use in the United States or most other Western countries, and any therapeutic use should be directed and supervised by a qualified clinician.

Lyophilized (before reconstitution)

Multiple vendor sources cite ~24 months at −20°C, ~12 months at 2–8°C (refrigerator), and up to ~6 months at room temperature if the vial remains sealed and dry. Keep away from light and humidity.

Reconstituted

Vendor sources show a wider spread than for BPC-157/TB-500/GHK-Cu: 7–14 days on the conservative end, up to 28 days on the permissive end, refrigerated (2–8°C) in bacteriostatic water. Never freeze. Because the disagreement across sources is larger, this should be treated as lower-confidence guidance than the more consensus-driven peptides in this tier. This is a vendor-derived convention rather than a peptide-specific stability study — the window traces to the 0.9% benzyl alcohol preservative's antimicrobial validation, not to a Semax-specific assay. See the Storage & handling primer for context.

For general storage chemistry (bacteriostatic vs sterile water, freeze-thaw, BUD framework), see Storage & handling.

Last reviewed: July 1, 2026

The most commonly reported pairing is Semax with Selank, another Russian-developed peptide with predominantly anxiolytic and GABAergic properties. The theoretical rationale is complementarity: Semax is primarily neurotrophic and activating (BDNF upregulation, serotonergic modulation), while Selank is proposed to reduce stress and anxiety without sedation. A functional connectome study examined both peptides' effects on resting-state brain networks and found anatomically distinct activity patterns. However, no published clinical trial has tested the combination against either agent alone in a human population; this pairing is anecdotal in terms of benefit-over-monotherapy.

Community users also report combining Semax with choline precursors such as alpha-GPC or CDP-choline on the hypothesis that cholinergic support complements BDNF-mediated memory consolidation, and with racetam-class compounds (e.g., piracetam, aniracetam) for putative synergistic nootropic effect. Neither combination has any clinical trial evidence. All such stacks should be regarded as entirely anecdotal, and potential pharmacokinetic or pharmacodynamic interactions have not been studied.

Semax is not currently FDA-approved for any indication. Effective April 22, 2026, the FDA removed Semax from Category 2 of its Section 503A bulk drug substances list after the original nominators withdrew their nominations. This removal lifts the prior “significant safety risk” designation but does not place Semax on the 503A Bulks List. Compounding pharmacies may prepare it with a valid physician prescription and pharmaceutical-grade API from an FDA-registered manufacturer. The FDA’s Pharmacy Compounding Advisory Committee (PCAC) is scheduled to review this substance at its July 23–24, 2026 public meeting. Removed from FDA Category 2 effective April 22, 2026. Selected for PCAC review Day 2 — July 24, 2026. PCAC agenda: DSIP (Emideltide), Semax, Epitalon. NOT currently on 503A Bulks List — requires physician Rx. Source: FDA Advisory Committee Calendar / Lengea Law, May 2026.

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Reported side effects: Generally safe. Possible: overstimulation, sleep disturbances if taken late

Intranasal Semax has a generally favorable short-term safety record in Russian clinical use. Published studies have administered intranasal doses of 600 mcg to 12 mg daily for up to 10 consecutive days without documented serious adverse events.

Reported adverse effects include:

• Nasal irritation or congestion (most frequent, attributable to the intranasal vehicle) • Headache • Mild insomnia, consistent with the peptide's stimulatory profile • Mild anxiety or agitation at higher doses; a single-dose human study at 16 mcg/kg noted stimulant-like effects with slightly elevated anxiety in some participants • Paradoxical worsening of anxiety has been reported anecdotally in individuals predisposed to anxiety disorders

A theoretical concern raised in the literature is the potential for increased hair loss in men with androgenetic alopecia, inferred from BDNF's known role in hair follicle cycling. This has not been documented in clinical populations.

Safety of injectable Semax has not been evaluated in any human clinical trial. Subcutaneous administration carries standard injection-site risks: local pain, irritation, redness, and infection.

No drug interaction data exist. Safety during pregnancy and lactation is not established. Long-term safety data are absent for all routes. The absence of severe adverse event reports likely reflects the small scale and Russian-publication context of available studies rather than a fully characterized safety profile. Users outside of supervised clinical settings operate without established safety parameters.