Semax
Nootropic peptide (ACTH(4-10) analog)
Also Semax peptide, NA-Semax, N-acetyl Semax, Semax amidate, Semax nasal, ACTH(4-7)PGP
- Evidence
- BSome human evidence
- FDA status
- Not approvedas of 2026-10-26
- Route
- Nasal
- Studies cited
- 5 human2 animal or cell
A nasal spray sold to sharpen memory and protect the brain after stroke. Studies from Russia look promising, but none was a proper blinded trial.
Sold for
Semax is sold as a nasal nootropic that sharpens memory and attention and protects the brain after stroke.
Studies say
Russian clinical studies report faster recovery after stroke and fewer vascular events in chronic cerebrovascular disease, and a small imaging study shows it changes brain network activity in healthy people, but no blinded placebo-controlled trial has been published, so the cognitive claims are unproven.
Why grade B. Five Russian clinical studies cover stroke (30 patients versus 80 controls in 1997; 110 patients in 2018), chronic cerebrovascular insufficiency (187 patients), optic nerve disease and a 24-person imaging study in healthy volunteers. Several had control groups but none describes randomization and blinding in the way a modern trial would, and none has been replicated outside Russia. Controlled human studies exist, so B, but at the weak end. 36781011
FDA. Semax is not approved by the FDA for any use and is sold in the United States as a research chemical. It is registered as a prescription drug in Russia. In July 2026 the FDA's Pharmacy Compounding Advisory Committee voted to recommend adding semax to the list of substances pharmacies may compound, against the advice of FDA staff; that recommendation has no legal effect until the FDA acts on it. 2513
Written from 13 cited sources. Last refreshed 2026-10-27. Not physician reviewed.
What this means for you
- What people take it for
- Memory, focus and stroke recovery
- Can a US doctor prescribe it?
- No. It is not approved and is sold as a research chemical. It is a prescription drug in Russia.
- Properly tested in people?
- Partly: several Russian studies of up to 187 patients, none properly blinded.
Evidence checklist
- Randomised controlled trial Controlled but not clearly randomizedno
- Human study over 100 people 187 patients in the largest studyyes
- More than one research group Studies from Russian groupsno
- Clinical outcomes, not surrogate markers Stroke recovery and Barthel indexyes
- Human safety data beyond case reports FDA staff found data insufficientno
Drawn from the cited studies below. A dash means the sources give no information.
What it is
Semax is a synthetic seven-amino-acid peptide made from the fourth to seventh amino acids of ACTH, the pituitary hormone that drives cortisol release, with a three-amino-acid tail (Pro-Gly-Pro) added to slow its breakdown. The fragment was chosen because ACTH(4-10) affects attention and learning in animals without raising cortisol. Semax was developed at the Institute of Molecular Genetics in Moscow and registered in Russia in the 1990s as a nasal solution for stroke, brain injury and cognitive complaints. 13
In the United States, semax is sold by research chemical vendors and has drawn FDA attention through the compounding system. It was nominated for the list of substances pharmacies can compound, and in 2026 the FDA's advisory committee reviewed it with six other peptides. FDA scientific staff recommended against all seven, citing insufficient evidence of safety and effectiveness; the committee nonetheless voted to recommend semax and five others. 251213
How it works
The strongest mechanistic finding is that semax raises brain-derived neurotrophic factor (BDNF), a protein that supports neuron survival and the growth of new connections. In rats it increased BDNF and nerve growth factor in the hippocampus within hours, and in stroke patients it raised blood BDNF levels that stayed high through the study period. Semax also increased serotonin turnover and amplified amphetamine-driven dopamine release in rat striatum, which is the proposed basis for its effects on attention. A review of its pharmacology lists additional actions on inflammation-related genes and on the breakdown of enkephalins. How much of any of this happens at nasal doses in humans is not known. 1496
What human research shows
The 1997 stroke study treated 30 patients in the acute phase of hemispheric ischemic stroke with semax added to standard care and compared them with 80 patients of similar severity on standard care alone. Neurological recovery, especially of motor function, was faster in the semax group, and EEG and evoked potential measures improved. The 2018 study followed 110 patients in early or late rehabilitation after stroke, with and without semax: semax raised blood BDNF and was associated with faster gains on the Barthel index of daily functioning. Neither study describes randomization or blinding. 611
In 187 patients with chronic cerebrovascular insufficiency, a 2005 study reported clinical improvement, stabilization of disease course and fewer strokes and transient ischemic attacks with semax, with few side effects. A 2000 ophthalmology study added nasal semax to standard therapy for optic nerve disease and reported better visual acuity, visual fields and nerve conduction than in the control group. 78
The one study in healthy people is a resting-state functional MRI experiment in 24 volunteers given nasal semax or placebo. Semax increased the volume of the medial frontal component of the default mode network within 20 minutes. That shows the peptide does something measurable in the brain; it does not show that memory or attention improve. 10
| Study | Model | Finding |
|---|---|---|
| Acute ischemic stroke, 1997 | Humans, n=30 treated versus 80 controls, controlled, not randomized | Faster recovery of neurological and motor function with semax added to standard care. 11 |
| Stroke rehabilitation and BDNF, 2018 | Humans, n=110 after ischemic stroke, controlled, not randomized | Semax raised blood BDNF and was associated with faster improvement on the Barthel index. 6 |
| Chronic cerebrovascular insufficiency | Humans, n=187, comparative study | Clinical improvement and fewer strokes and transient ischemic attacks reported with semax. 7 |
| Default mode network fMRI | Humans, n=24 healthy volunteers, placebo-controlled | Nasal semax increased the frontal component of the default mode network within 20 minutes. 10 |
| BDNF and NGF in rat brain | Rats | Semax raised BDNF and nerve growth factor levels in the hippocampus. 4 |
Safety
The Russian studies describe semax as well tolerated, including in older patients, with a low rate of side effects, mostly nasal irritation. FDA staff reviewing it for compounding in 2026 concluded the published data were insufficient to establish safety, pointing to the lack of controlled trials, pharmacokinetic data and long-term follow-up. Because it is derived from ACTH, effects on the stress hormone system and on mood with sustained use are theoretical concerns that have not been studied. Products sold online are unregulated. 2712
Questions for your clinician
- Are there controlled trials outside Russia of semax?
- How does semax compare with stroke rehabilitation options?
- What did FDA staff conclude about its safety data?
Questions people ask
What approvals does semax hold?
No. It is approved only in Russia. In the United States it is sold as a research chemical, and a July 2026 advisory committee vote recommending it for pharmacy compounding does not change its status until the FDA issues a rule. 2513
What has semax been studied for in Russia?
Acute stroke and stroke rehabilitation, chronic cerebrovascular insufficiency, optic nerve disease, and in healthy volunteers for its effect on brain networks. The stroke and cerebrovascular studies are the largest, at 110 and 187 patients. 6781011
What is the proposed mechanism behind semax?
The best-supported effect is an increase in BDNF, a growth factor for neurons, shown in rats and in stroke patients' blood. It also affects serotonin and dopamine signaling in rat brain. These are plausible routes to neuroprotection and attention effects, but they have not been linked to cognitive outcomes in a controlled human trial. 1469
How strong is the research behind semax?
Low by Western standards. The clinical studies come from a few Russian centers, several lack randomization or blinding, the imaging study had 24 people, and nothing has been replicated independently. FDA staff reached the same conclusion in 2026. 212
Does it cause any adverse reactions?
The Russian literature reports few, mainly nasal irritation, and describes semax as well tolerated in older patients. There is no systematic safety data, no long-term follow-up and no information on interactions, so the honest answer is that the side effect profile is unknown. 712
Citations
- Neuropeptides 2020: review of semax pharmacology and clinical studies doi.org
- STAT, July 2026: FDA peptide compounding panel outcomes statnews.com
- Drug Test Anal 2019: analytical and pharmacological review of semax and selank doi.org
- Cell Mol Neurobiol 2009: semax and BDNF and NGF expression in rat hippocampus doi.org
- FDA: Pharmacy Compounding Advisory Committee materials on semax, 2026 fda.gov
- Zh Nevrol Psikhiatr 2018: semax and rehabilitation timing after ischemic stroke pubmed.ncbi.nlm.nih.gov
- Zh Nevrol Psikhiatr 2005: semax in chronic cerebrovascular insufficiency pubmed.ncbi.nlm.nih.gov
- Vestn Oftalmol 2000: semax in optic nerve disease pubmed.ncbi.nlm.nih.gov
- Neurochem Res 2005: semax effects on serotonin and dopamine in rat striatum doi.org
- Lebedeva 2018, Bull Exp Biol Med: effects of semax on the default mode network pubmed.ncbi.nlm.nih.gov
- Gusev 1997, Zh Nevrol Psikhiatr: semax in acute hemispheric ischemic stroke pubmed.ncbi.nlm.nih.gov
- FDA: interim 503A bulk drug substances category list fda.gov
- Healio, July 2026: FDA committee recommends looser restrictions for several peptides healio.com