Semax is a heptapeptide (Met-Glu-His-Phe-Pro-Gly-Pro) developed at the Institute of Molecular Genetics of the Russian Academy of Sciences in the late 1980s and early 1990s. It is a synthetic analogue of the ACTH(4-10) fragment — the portion of adrenocorticotropic hormone responsible for cognitive and neuroprotective effects — with a C-terminal Pro-Gly-Pro extension that dramatically increases resistance to proteolytic degradation and extends functional half-life. Semax has been registered as a pharmaceutical drug in Russia since 1999 and is used clinically for stroke recovery, cognitive impairment, and neuroprotection.
Key Takeaways
- —Semax is ACTH(4-10)-Pro-Gly-Pro, a synthetic heptapeptide registered as a drug in Russia for stroke and cognitive impairment since 1999. It has no equivalent Western regulatory approval.
- —Semax upregulates BDNF (brain-derived neurotrophic factor) and NGF in the hippocampus within 1 hour of administration in rat models — the fastest BDNF upregulation mechanism of any known peptide (Dolotov et al., J Neurochem, 2006).
- —Unlike ACTH itself, Semax produces no HPA axis activation — it does not increase cortisol, ACTH, or adrenal hormones at therapeutic doses, because it lacks the receptor-binding N-terminal sequence responsible for steroidogenesis.
- —Administered intranasally: bypasses the blood–brain barrier via olfactory ensheathing cells, achieving CNS delivery without injection.
The full ACTH peptide (39 amino acids) is known for two distinct functions: the N-terminal sequence (ACTH 1-17) stimulates adrenocortical steroidogenesis — triggering cortisol release. The mid-chain fragment (ACTH 4-10: Met-Glu-His-Phe-Pro-Gly) is responsible for the cognitive-enhancing and neuroprotective effects, operating through melanocortin receptors (MC4R) in the CNS and independently through neurotrophin upregulation.
Semax retains the ACTH 4-10 sequence but deliberately lacks the steroidogenic N-terminus. The Pro-Gly-Pro extension added by Zakharova and Myasoedov's team confers two advantages: markedly increased resistance to dipeptidyl peptidase and other CNS proteases, and enhanced CNS penetration via intranasal administration. The result is a compound with ACTH's cognitive effects but none of ACTH's hormonal side effects.
The fact that Semax doesn't activate the HPA axis is not incidental — it's the design objective. The ACTH 4-10 fragment was known to improve learning and memory in animal models since the 1970s (De Wied, Utrecht), but as a therapeutic was unusable because ACTH stimulated cortisol release. Semax solved this problem structurally, not pharmacologically. This is an elegant example of rational peptide engineering that produced a clinically usable compound from basic research.
BDNF and NGF upregulation: The most important finding in the mechanistic literature. Dolotov et al. (2006) demonstrated that intranasal Semax in rats produced a 140% increase in BDNF mRNA in the hippocampus and frontal cortex within 1 hour of administration. NGF levels were similarly elevated. BDNF is the principal mediator of synaptic plasticity, neurogenesis, and long-term potentiation — the molecular basis of learning and memory consolidation.
Melanocortin receptor activation (MC4R): Semax binds melanocortin receptors in the prefrontal cortex and limbic system, activating cAMP signalling pathways involved in attention, working memory, and cognitive flexibility.
Neuroprotection via oxidative stress mitigation: In ischaemia models, Semax reduces glutamate excitotoxicity, attenuates oxidative damage, and upregulates antioxidant gene expression. This is the mechanism underlying its use in stroke recovery.
Dopamine and serotonin system modulation: Semax increases dopamine turnover in mesocortical pathways without the tolerance, dependence, or receptor downregulation associated with direct dopamine agonists. Serotonin synthesis genes are also upregulated in hippocampal tissue.
Intranasal Semax produced a 140% increase in BDNF mRNA expression in the hippocampus within 1 hour of administration in rat models, making it the fastest-acting BDNF upregulator of any studied compound (Dolotov et al., Journal of Neurochemistry, 2006). BDNF elevation at this magnitude is comparable to the effects of 4–6 weeks of aerobic exercise — achieved in a single acute dose, with the important caveat that animal-to-human extrapolation requires independent validation.
Semax's clinical evidence base is predominantly from Russian trials, which are harder to access and evaluate than Western clinical data. The strongest published findings:
Stroke and cerebrovascular disease: Multiple Russian clinical trials report improved neurological outcome scores, faster functional recovery, and reduced cognitive deficit at 30-day follow-up in ischaemic stroke patients receiving Semax (6–12 mcg/kg/day intranasal) versus standard care. A review covering 10 trials and ~500 patients was published by Andreeva et al. (2000).
Optic nerve disease: A published RCT in patients with optic nerve disease (glaucomatous neuropathy) showed Semax improved visual acuity and visual field measures versus placebo. This is one of the more methodologically robust Semax trials.
Cognitive function in healthy subjects: Smaller studies in healthy volunteers report improvements in sustained attention, working memory recall, and processing speed. These studies have small sample sizes (N=20–60) and lack long-term follow-up data.
The key limitation is that Semax's clinical evidence base has not been replicated in large prospective RCTs conducted under Western GCP. The compound is registered in Russia as a drug — which means it has met Russian regulatory standards — but is not in the EMA or FDA-approved drug database.
Semax's most distinctive feature from a practical standpoint is its intranasal delivery. The olfactory epithelium allows direct CNS delivery via olfactory ensheathing cells — bypassing the blood-brain barrier entirely. This is not a theoretical claim; Semax's nasal route is the one used in the registered Russian pharmaceutical product and in virtually all published clinical research.
| Parameter | Protocol |
|---|---|
| Route | Intranasal (primary) — SC injection also used in some protocols |
| Dose | 200–600 mcg/day intranasal (typical research protocol) |
| Frequency | Once or twice daily |
| Concentration | Available as 0.1% (100 mcg/drop) or 1% (1000 mcg/drop) nasal solution |
| Timing | Morning administration preferred (aligns with natural BDNF synthesis peaks) |
| Cycle | 2–4 weeks on, 2 weeks off |
Practical note: The registered Russian product (produced by Peptide Technologies, Moscow) comes as a pre-mixed nasal solution. Research-grade Semax is typically lyophilised powder requiring reconstitution in bacteriostatic water or saline, then administered via a nasal spray bottle (atomised for even mucosal distribution).
Semax has been in clinical use in Russia since 1999 — giving it a post-market safety record exceeding 25 years. No serious adverse events have been attributed to Semax at clinical doses in any published series. Notable safety characteristics:
Semax has been registered as a pharmaceutical in the Russian Federation since 1999 and has been in continuous clinical use for over 25 years. Published adverse event data and post-market pharmacovigilance in Russian clinical settings have not identified serious safety signals. The compound's lack of HPA axis activation distinguishes it from ACTH itself and eliminates the hypothalamic–pituitary–adrenal adverse effect profile as a concern at therapeutic doses.
Semax exists in a regulatory grey zone that most vendor sites don't explain clearly — and the BDNF/ACTH mechanism data deserves more scrutiny than product listings typically offer. The Next Pep peptide library covers the full heptapeptide profile: the ACTH(4-10)-Pro-Gly-Pro structure, BDNF upregulation mechanism, Russian pharmaceutical status, intranasal pharmacokinetics, and the stroke recovery versus cognitive enhancement evidence — all cross-referenced against primary sources.
Use the comparison tool to put Semax alongside Selank or other nootropic peptides side-by-side — comparing mechanisms, evidence quality, and delivery routes. For injectable or intranasal protocols, the dosing calculator helps with reconstitution: enter your vial concentration and target dose and it returns exact volume.
Both are Russian-developed intranasal peptides registered as pharmaceuticals in Russia. Semax (ACTH analogue) is primarily cognitive-enhancing and neuroprotective via BDNF/NGF upregulation and melanocortin activation. Selank (Tuftsin analogue) is primarily anxiolytic via GABA modulation and enkephalin degradation inhibition. They target different receptor systems and are often combined: Semax for focus and cognitive performance, Selank for anxiety reduction and stress resilience. They don't overlap mechanistically.
Semax is not scheduled and not FDA-approved. In the US it occupies a legal grey area: it's not a controlled substance, but purchasing it as a drug for human use is not authorised. Research-grade Semax is sold by peptide suppliers for in-vitro research use. The regulatory situation mirrors that of most unapproved research peptides.
BDNF upregulation in animal models occurs within 1 hour of intranasal administration. Human studies on cognitive performance don't provide precise onset data, but anecdotal reports consistently describe effects within 15–45 minutes of nasal administration, consistent with the rapid CNS delivery mechanism. Duration is typically 4–8 hours.
Semax's mechanisms — BDNF upregulation, dopamine turnover increase, sustained attention improvement — are mechanistically relevant to ADHD. Some published Russian data included patients with attention disorders. However, there are no randomised controlled trials specifically in ADHD-diagnosed patients meeting Western diagnostic criteria, and this remains an off-label extrapolation.
This article is for research and educational purposes only. Semax is not FDA-approved and is not available as a prescription pharmaceutical in the United States. Consult a licensed healthcare professional before considering any peptide protocol.
Research Disclaimer. All content on Next Pep is for informational and educational purposes only. It does not constitute medical advice, diagnosis, or treatment. Consult a licensed healthcare professional before considering any peptide protocol.
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