Semax Peptide: Complete Guide

Semax is a synthetic peptide based on a fragment of adrenocorticotropic hormone (ACTH), specifically the 4-7 amino acid sequence (Met-Glu-His-Phe), with a stabilizing Pro-Gly-Pro tripeptide attached to its C-terminus. Developed in the 1980s at the Institute of Molecular Genetics of the Russian Academy of Sciences, it’s been approved in Russia since the 1990s as a prescription treatment for stroke, cognitive disorders, and optic nerve disease [1][2]. It’s one of the most research-backed compounds in peptide therapy.

What sets Semax apart from most nootropic compounds is the depth of its research. It directly upregulates brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) — two proteins that are fundamental to neuronal survival, growth, and synaptic plasticity. This isn’t a stimulant effect. It’s a structural change in how the brain maintains and builds neural connections [3][4].

Semax is frequently compared to Selank, its sibling peptide from the same research institute. Both are approved in Russia, both are administered nasally, and both affect the brain — but through different primary mechanisms. For the full picture of cognitive-enhancing peptides, see our guide on peptides for cognitive function.

Key Takeaways

Semax is an ACTH(4-7) analog that upregulates BDNF and NGF expression in the brain, supporting neuronal growth and cognitive function
Approved in Russia for acute ischemic stroke, cognitive disorders, and optic nerve disease — backed by clinical trials showing improved neurological outcomes
Standard nasal dosing is 200–600 mcg per day, with effects lasting 20–24 hours per dose due to the PGP stabilizing sequence
No significant side effects reported across decades of clinical use in Russia

What Is Semax?
How Semax Works
Clinical Evidence
Semax Dosing
Side Effects and Safety
Semax vs Selank
Legal Status
FAQ
Sources

What Is Semax?

The ACTH molecule is a 39-amino acid peptide produced by the pituitary gland. Its primary role is stimulating the adrenal cortex to produce cortisol. But researchers noticed that fragments of the ACTH molecule — particularly the 4-10 segment — had cognitive and neurotrophic effects independent of adrenal stimulation [1].

The problem, as with many peptides, was stability. The ACTH(4-7) fragment breaks down in minutes when exposed to blood or brain enzymes. Soviet researchers solved this in the 1980s by attaching the Pro-Gly-Pro (PGP) sequence to the C-terminus, creating a seven-amino acid peptide with a biological half-life of 20–24 hours instead of minutes [1][5].

The resulting compound — Semax (MEHFPGP) — retained the neurotrophic and cognitive effects of the ACTH fragment while eliminating the hormonal effects on the adrenal glands. It doesn’t raise cortisol. It doesn’t affect the HPA axis. It works exclusively through neurotrophin signaling and related pathways [2][5].

Semax was first registered in Russia in 1994. It’s available as a 0.1% and 1% nasal spray, prescribed for stroke recovery, cognitive impairment, and optic nerve atrophy. It remains one of the few peptide drugs with extensive human clinical data and long-term safety records [2]. You can find it among other noteworthy compounds on our list of peptides.

How Semax Works

Semax’s mechanism of action centers on neurotrophic factor regulation, with several downstream effects on brain function.

BDNF Upregulation

Brain-derived neurotrophic factor is arguably the most studied molecule in neuroplasticity research. It promotes neuronal survival, encourages new synapse formation, and strengthens existing synaptic connections. Low BDNF levels are associated with depression, cognitive decline, and neurodegeneration [3]. This BDNF connection is one reason Semax is increasingly discussed in the context of peptides for depression.

Semax directly increases BDNF gene expression in the hippocampus — the brain region responsible for learning and memory. A study by Dolotov et al. (2006) showed that a single Semax administration produced a 1.4-fold increase in BDNF mRNA expression in the rat hippocampus, with effects lasting at least 24 hours. It also increased expression of the TrkB receptor, which is the primary receptor through which BDNF exerts its effects [3].

In stroke models, this BDNF upregulation was even more pronounced. Filippenkov et al. (2015) demonstrated that Semax activated transcription of BDNF, NGF, and their receptors in brain tissue during ischemic conditions — exactly when neuroprotection is most needed [4].

NGF Upregulation

Nerve growth factor is particularly important for cholinergic neurons — the neurons most affected in Alzheimer’s disease and age-related cognitive decline. Semax increases NGF expression in brain tissue, providing trophic support to these vulnerable neuronal populations [4][6].

The combined BDNF + NGF upregulation is relatively unique among nootropic compounds. Most substances affect one or the other. Semax does both, which may explain its broad cognitive effects.

Dopamine and Serotonin Modulation

Beyond neurotrophins, Semax affects monoamine neurotransmitter systems. Research has shown it modulates dopaminergic and serotonergic turnover in the striatum and hippocampus, increasing the availability of both neurotransmitters in key brain regions [7]. This likely contributes to the improvements in attention, motivation, and mood that users report. While Semax isn’t primarily an anxiolytic, its mood-enhancing effects make it a useful complement for those dealing with anxiety.

Anti-inflammatory and Neuroprotective Effects

In cerebral ischemia models, Semax reduced the expression of inflammatory genes (including several interleukins and vascular adhesion molecules) while upregulating genes involved in neuronal survival [8]. This dual action — reducing inflammation while simultaneously promoting neurotrophic support — makes it particularly relevant for stroke recovery and neurodegenerative conditions.

For more on how peptides interact with biological systems, see how do peptides work.

Clinical Evidence

Acute Ischemic Stroke

This is Semax’s strongest clinical indication and the basis for its Russian regulatory approval.

A multicenter clinical trial evaluated Semax (1% nasal spray, 12 mg/day for 5 days) in patients with acute ischemic stroke. Patients who received Semax within 6 hours of stroke onset showed significantly better neurological recovery at 21 days compared to the control group, as measured by the National Institutes of Health Stroke Scale (NIHSS) and the Barthel Index of daily living activities [9].

The study by Gusev et al. (2018) confirmed that Semax administration during ischemic stroke was associated with increased plasma BDNF levels, which remained elevated throughout the treatment period. Higher BDNF levels correlated positively with better neurological outcomes at follow-up [9].

A separate study found that Semax at the 1% concentration (the higher-dose formulation approved for stroke) reduced infarct volume in the acute phase and improved functional outcomes at 30 and 90 days post-stroke [10].

Cognitive Disorders

The 0.1% Semax formulation is approved in Russia for cognitive disorders, including those related to cerebrovascular disease, neurosurgical recovery, and age-related cognitive decline.

Clinical studies showed improvements in attention, memory, and information processing speed in patients with chronic cerebrovascular insufficiency. One trial reported significant improvement on multiple neuropsychological test batteries after a 10-day course of Semax nasal spray, with effects persisting for at least 30 days after treatment ended [11].

Optic Nerve Disease

Semax is approved in Russia for optic nerve atrophy and glaucomatous optic neuropathy. The rationale is that neurotrophic factors, particularly BDNF and NGF, are critical for retinal ganglion cell survival. Clinical trials showed improvements in visual acuity and visual field measurements in patients with optic nerve disease treated with Semax, though the evidence base is smaller than for stroke [12].

Cognitive Enhancement in Healthy Individuals

While most clinical data comes from disease populations, animal studies consistently show that Semax improves learning and memory in healthy subjects. Rats treated with Semax showed enhanced performance in conditioned avoidance tasks, Morris water maze tests, and novel object recognition — standard tests of different memory types [3][5].

Human studies in healthy volunteers are limited but suggest improvements in attention and working memory, particularly under stress conditions [11].

Semax Dosing

Standard Protocol (Nasal)

Semax is available in two concentrations in Russia, each for different indications:

0.1% solution (cognitive support):

Dose: 200–600 mcg per day
Administration: 2–3 drops per nostril, 2–3 times daily
Duration: 10–14 day courses, repeatable after a 2-week break
Indication: Cognitive disorders, neuroprotection, cognitive enhancement

1% solution (stroke):

Dose: 6–12 mg per day
Administration: 2–3 drops per nostril, 4–6 times daily
Duration: 5–14 days starting immediately after stroke onset
Indication: Acute ischemic stroke (clinical setting)

Practical Guidance

For nootropic use, most practitioners start at the lower end (200 mcg/day) and titrate up based on response. The long biological half-life (20–24 hours) means once-daily dosing can be effective, though splitting the dose morning and midday is common [5].

Semax should be administered during waking hours. Its alerting properties can interfere with sleep if taken in the evening. For general timing advice, see when to take peptides.

Some users cycle Semax — 2 weeks on, 2 weeks off — to match the Russian clinical protocol. Others use it continuously at lower doses. There’s no clear evidence that tolerance develops, but the cycling approach mirrors the studied protocol [11].

For information on preparing injectable peptides (though Semax is primarily nasal), see how to reconstitute peptides.

Side Effects and Safety

Semax has been used clinically in Russia for over 25 years, and the safety data is reassuring.

Reported side effects:

Nasal irritation or dryness (the most common complaint with chronic use)
Mild headache during the first 1–2 days (typically resolves)
Occasional dizziness (rare)

Notable safety features:

No effect on cortisol levels or HPA axis function (despite being an ACTH derivative)
No cardiovascular effects reported
No addiction or dependence potential
No withdrawal symptoms after discontinuation
No reported drug interactions (though formal interaction studies are limited)
No mutagenic or teratogenic effects observed in preclinical studies [2]

The N-Acetyl Semax Amidate (NASA) variant, sometimes found in research markets, is a modified form with reportedly stronger effects. Safety data on this variant is much more limited than on standard Semax, and it has not been through clinical trials.

For a general overview of peptide safety considerations, see are peptides safe and peptide side effects.

Semax vs Selank

Both peptides come from the Institute of Molecular Genetics and are approved prescription drugs in Russia. They’re complementary rather than competing compounds.

Feature	Semax	Selank
Base molecule	ACTH(4-7) + PGP	Tuftsin + PGP
Primary effect	Cognitive enhancement, neuroprotection	Anxiolytic, nootropic
BDNF upregulation	Strong (primary mechanism)	Moderate
NGF upregulation	Yes	Not established
GABA modulation	Minimal	Strong (primary mechanism)
Stimulating vs calming	More stimulating/alerting	More calming/anxiolytic
Russian approvals	Stroke, cognitive disorders, optic nerve	GAD, neurasthenia
Typical dose	200–600 mcg/day nasal	200–400 mcg/day nasal
Duration of effect	20–24 hours	6–8 hours

Choose Semax when: The goal is cognitive performance, neuroprotection, focus, or recovery from neurological events. Semax is the more stimulating of the two and better suited for demanding cognitive tasks.

Choose Selank when: Anxiety is the primary concern, or when cognitive issues are secondary to stress and emotional dysregulation. Selank addresses the emotional foundation first. For a deeper dive into peptide options for anxiety, see our guide to peptides for anxiety.

Combining both: Some practitioners prescribe Semax and Selank together — Semax for cognitive drive and Selank for anxiety management. The mechanisms don’t conflict: Semax works primarily through neurotrophins while Selank works through GABA modulation. There are no published clinical trials on the combination, but the pharmacology supports compatibility. For more on combining peptides strategically, see our best peptide stack guide.

Legal Status

Russia: Approved prescription drug since 1994. Available as Semax 0.1% (cognitive disorders) and Semax 1% (stroke). Widely used in neurological practice.

United States: Semax is not FDA-approved and is not available as a commercial pharmaceutical. It may be accessible through compounding pharmacies with a physician’s prescription, subject to current FDA compounding regulations. Check our guides on peptide legality and the FDA peptide reclassification for current status.

Other countries: Not widely approved outside Russia and some CIS countries. Available as a research compound in many jurisdictions.

For information on obtaining peptides through legitimate channels, see how to get peptides prescribed and peptide therapy online.

Explore the evidence: See all 7 Semax studies in our research database, or browse the full peptide therapy statistics for 2026.

FAQ

Does Semax actually improve cognition?▼

Animal studies consistently show improved learning and memory. Human clinical trials in cognitively impaired patients show significant improvements in attention, memory, and processing speed. Data in healthy humans is more limited but suggestive. The BDNF and NGF upregulation provides a plausible biological mechanism for these effects [3][4][11].

How long does it take for Semax to work?▼

Nasal Semax produces detectable effects within 15–30 minutes of administration, with peak effects at 1–2 hours. The biological half-life is 20–24 hours, meaning one dose lasts most of the day. Full therapeutic benefits in clinical settings typically build over a 10–14 day course [5][11].

Does Semax raise cortisol?▼

No. Despite being derived from ACTH, the 4-7 fragment used in Semax does not activate the adrenal cortex. It has no effect on cortisol production or the hypothalamic-pituitary-adrenal axis. This was specifically confirmed in clinical studies [2][5].

Can I use Semax and Selank together?▼

Yes, many practitioners use them together. Semax provides cognitive stimulation via BDNF/NGF pathways while Selank provides anxiolytic effects via GABA modulation. There are no known pharmacological conflicts. A common approach is Semax in the morning for cognitive drive and Selank throughout the day for anxiety management.

Is Semax a stimulant?▼

Not in the traditional sense. Semax doesn’t work through catecholamine release like amphetamines or through adenosine blockade like caffeine. Its alerting effects come from enhanced neurotrophin signaling and modulation of dopaminergic/serotonergic pathways. Users describe it as “cleaner” than stimulants — improved focus without jitteriness, crash, or dependence [7].

Sources

Ashmarin IP, et al. Design and investigation of an ACTH 4-10 analogue lacking D-amino acids and having prolonged neurotropic activity. Neuroscience Research Communications. 1995;16(2):105-112.
Eremin KO, et al. Semax, an ACTH(4-10) analogue with nootropic properties, activates dopaminergic and serotoninergic brain systems in rodents. Neurochemical Research. 2005;30(12):1493-1500. doi:10.1007/s11064-005-8826-8
Dolotov OV, et al. Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus. Brain Research. 2006;1117(1):54-60. doi:10.1016/j.brainres.2006.07.108
Filippenkov IB, et al. Effect of semax and its C-terminal peptide PGP on expression of neurotrophins and their receptors in rat brain during incomplete global ischemia. Molecular Biology. 2015;49(3):402-411. doi:10.1134/S0026893315020053
Kolomin TA, et al. Transcriptomic response in rat frontal cortex after chronic oral administration of the nootropic peptide Semax. Medical Science Monitor. 2013;19:135-143. doi:10.12659/MSM.883744
Agapova TY, et al. Effect of semax on the temporary dynamics of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) gene expression in the rat hippocampus. Doklady Biological Sciences. 2008;418:48-50.
Eremin KO, et al. Semax activates dopaminergic and serotoninergic brain systems in rodents. Neurochemical Research. 2005;30:1493-1500. doi:10.1007/s11064-005-8826-8
Dergunova LV, et al. Genome-wide transcriptome analysis using RNA-Seq reveals a large number of differentially expressed genes in a transient MCAO rat model. BMC Genomics. 2018;19(1):655. doi:10.1186/s12864-018-5039-5
Gusev EI, et al. The efficacy of semax in the treatment of patients at different stages of ischemic stroke. Zhurnal Nevrologii i Psikhiatrii imeni S.S. Korsakova. 2018;118(3):61-68. doi:10.17116/jnevro201811831
Medvedev SV, et al. Semax in the prevention and treatment of cerebral ischemia. Bulletin of Experimental Biology and Medicine. 2006;142(1):108-111.
Kaplan AY, et al. Synthetic ACTH analogue semax displays nootropic-like activity in humans. Neuroscience Research Communications. 1996;19(2):115-123.
Polunin GS, et al. Evaluation of therapeutic effect of new drug semax in optic nerve disease. Vestnik Oftalmologii. 2000;116(1):15-18.