Semax: research, side effects and dosage in studies
In short
Semax is a synthetic peptide based on a short segment of the hormone ACTH that has been studied in small Russian patient studies without described randomisation [1] [2, 3, 5]B. It has no marketing authorisation in the EU [7]regulator.
- Semax has been studied in Russia mainly in the treatment and rehabilitation of stroke. The investigators report faster recovery of function, but the abstracts do not describe the study design [2, 3]B.
- The developers say Semax improves memory and attention, but we know of no published independent randomised memory trials [1] [13].
- In motor neuron disease Semax did not affect the course of the disease, only the quality-of-life score [11]B.
- Investigators describe Semax as well tolerated, but there are no figures for harms, and in one follow-up study the EEG showed paroxysmal activity [5]B [12]B.
- Annex 1 A of the Finnish medicines list names a modified form, N-acetyl-semax, but not plain Semax [9]regulator. Fimea warns against injectable peptides bought online [8]regulator.
What is Semax?
Semax is a synthetic peptide derived from the 4-10 segment of the hormone ACTH (corticotropin) [1] [2]B. Its amino acid sequence is Met-Glu-His-Phe-Pro-Gly-Pro [10]B. Semax has been studied for effects on memory, attention and blood flow in the brain [1].
According to an overview published in 1997 by the developing group, Semax was given through the nose and had gone through the stages from basic research to practical use [1]. According to a 2026 review, Semax has been used in Russia for decades, but independent validation and systematic safety surveillance through Western regulatory frameworks are lacking [13].
In the EU Semax has no marketing authorisation [7]regulator. Basics: What are peptides?. All substances: Peptides A-Z.
Evidence at a glance
Each cell gives the kind of study and its source. The letter is the evidence level, not the result.
| Claimed effect | Humans | Animals | Cells |
|---|---|---|---|
| Recovery after stroke | 30 patients vs 80 on usual care [2]B; 110 rehabilitation patients, faster improvement on the Barthel index [3]B. No randomisation described | - | - |
| Cerebrovascular insufficiency | 187 patients; no control group or figures in the abstract [5]B | - | - |
| Stomach or duodenal ulcer | Ulcer healed by day 14 in 89.5% vs 30.8% of controls, added to ulcer drugs [10]B | - | - |
| Motor neuron disease | 27 patients, open-label: no effect on disease course, quality-of-life score improved [11]B | - | - |
| Memory and attention | Improved in healthy men according to the developers' overview; design not described [1] | Also in experimental animals according to the developers' overview [1]C | - |
| Brain activity on imaging | 14 received Semax and 10 placebo: larger front part of the resting-state network [4]B | - | - |
| Safety | Described as well tolerated without figures [5]B; paroxysmal EEG activity in some patients [12]B | - | - |
"-" = no such study is known.
What is Semax studied for?
Semax has been studied mainly in diseases of blood flow in the brain, in Russian studies, and no use is approved in the EU [2, 3, 5]B [7]regulator.
- Ischaemic stroke: the acute phase [2]B and rehabilitation [3]B.
- Cerebrovascular insufficiency: preventing progression and exacerbations [5]B.
- Brain damage after lack of oxygen: a follow-up of 73 patients [12]B.
- Other: hard-to-heal stomach or duodenal ulcer [10]B and motor neuron disease [11]B.
- Brain activity in healthy people: a small imaging study [4]B.
Online claims. Semax is marketed online for memory and focus. The claim rests mainly on the developers' own overview [1]. According to a 2026 review, efficacy and safety have not yet been shown in multicentre, randomised, placebo-controlled trials [13].
How does Semax work?
How Semax works is not known for certain. According to a 2026 review, the main mechanism of Semax is an increase in brain-derived neurotrophic factor (BDNF), and in animal stroke models it has changed the activity of genes in neurotransmitter and inflammation pathways [13]C.
In stroke survivors, blood BDNF rose in those who received Semax and stayed high throughout the study [3]B. In healthy volunteers Semax given through the nose changed the picture of the brain's resting-state network on MRI [4]B. These show changes in the body, not yet a benefit.
Has Semax been studied in humans?
Yes, but the studies are small. Almost all are Russian and published in Russian-language journals. The abstracts do not describe randomisation or blinding, which makes the results hard to judge [2, 3, 5]B.
Stroke and blood flow in the brain
- Acute ischaemic stroke (1997). 30 patients received Semax on top of usual care and were compared with 80 patients on usual care. The investigators reported some effect on how fast damaged functions, especially movement, recovered [2]B.
- Rehabilitation after stroke (2018). 110 patients were split into early and late rehabilitation groups and further into those who did and did not receive Semax. Those on Semax had a rise in blood BDNF, and the investigators report faster improvement on the Barthel index of daily living [3]B.
- Cerebrovascular insufficiency (2005). 187 patients. The investigators reported clinical improvement and fewer strokes and transient ischaemic attacks, but the abstract gives no control group and no figures [5]B.
- Brain damage after lack of oxygen (1999). 73 patients. The investigators report that treatment worked in patients with memory disorders [12]B.
Other studies
- Peptic ulcer (2002). Patients with hard-to-heal stomach or duodenal ulcers received Semax through the nose on top of standard ulcer drugs. On day 14 the ulcer had healed in 89.5% of those on Semax and 30.8% of controls. The investigators themselves say more clinical studies are needed [10]B.
- Motor neuron disease (2007). In an open-label study of 27 patients, Semax did not affect the loss of nerve supply or the clinical ratings. The overall quality-of-life score improved because of better mood and motivation [11]B.
- Brain imaging in healthy people (2018). 14 received Semax and 10 placebo. The Semax group had a larger front part of the brain's resting-state network than controls [4]B. This shows a change in brain activity, not a benefit.
- Memory in healthy people. According to the developers' overview, Semax improved memory and attention in healthy men under demanding conditions [1], but the overview is not independent and its abstract does not describe the study design.
Who studies Semax?
Almost all Semax research is Russian. Some patient studies were written by the same researchers who developed the substance: for example N. F. Myasoedov is an author of the developers' overview and of several human studies [1] [2, 4, 10, 11]B. E. I. Gusev recurs in the stroke studies [2, 3, 5]B.
Outside Russia there is a Belgian official laboratory's analysis of seized products [6]D and a 2026 review of peptides in ageing [13].
Author of this page: the editorial team
This page was written by the Molecular Recovery editorial team. The draft was made with the help of AI, and the claims have been checked against the sources (AI policy). The page has not been medically reviewed. How we work: About us.
What are the side effects of Semax?
The side effects of Semax are not well known. Investigators have described Semax as well tolerated, but the abstracts give no figures for harms, and no large independent safety studies have been published [1] [5]B [13].
What users report. In the Reddit accounts we compiled (not research), 27 of 72 people (38%) reported some harm, most often: anxiety, irritability or overstimulation (6, 8%), insomnia (5, 7%), fatigue or crash (3, 4%) and emotional blunting or low mood (3, 4%). People tend to post when something goes wrong, so this share does not tell how common harms are. The effects people report from Semax are feelings such as focus and alertness, and 31 people (43%) used Selank at the same time. The harms in detail: Semax user experiences.
What the studies say
- According to the developers' overview, Semax did not cause side effects or complications in any case [1]. This is the developers' own assessment.
- The authors of the 2005 study described side effects as minor and the drug as well tolerated, including in older patients [5]B.
- In follow-up of brain damage after lack of oxygen, the EEG in some cases showed paroxysmal activity after Semax was injected. The investigators therefore say the first injection should be given while monitoring the EEG [12]B.
What has not been studied
According to the 2026 review, Semax appears to have a favourable safety profile based on Russian experience, but independent validation and systematic safety surveillance through Western regulatory frameworks are lacking [13]. We know of no published studies of long-term use.
According to Fimea, there is no reliable information on the content, quality and safety of products sold as peptides. In injectables, impurities such as endotoxins can cause serious health harm [8]regulator. More: Side effects and safety.
Interactions and who has no data
Interactions have not been studied. Semax was given on top of other treatment: in stroke alongside intensive care or rehabilitation, and in peptic ulcer with standard ulcer drugs (omeprazole, De-Nol and Solcoseryl) [2, 3, 10]B. No conclusions about interactions can be drawn from these.
Because one follow-up study saw paroxysmal EEG activity after Semax was injected [12]B, data are missing especially for people prone to seizures. There are also no data for pregnancy or breastfeeding, or for children.
What speaks against it and what is unknown
The positive results come from small studies whose design is not described, and the only open-label study in a progressive disease showed no effect on its course [2, 3, 5, 11]B.
Counter-evidence
- In motor neuron disease Semax did not affect the loss of nerve supply or the clinical ratings [11]B.
- Researchers at a Belgian official laboratory wrote in 2020 that, to their knowledge, Semax and Selank had not completed any clinical trials [6]D.
- According to the 2026 review, efficacy and safety still need to be shown in multicentre, randomised, placebo-controlled trials [13].
- In follow-up of brain damage after lack of oxygen, the EEG in some cases showed paroxysmal activity [12]B.
What the evidence does not support
- "Semax improves memory in healthy people": the claim rests on the developers' overview, which does not describe the study design [1]. We know of no published independent randomised memory trials.
- "Brain scans prove a benefit": the imaging study showed a change in brain activity, not a benefit [4]B.
- "Semax is proven safe": there are no figures for harms, and systematic safety surveillance is lacking [5]B [13].
- "The vial always contains what the label says": according to Fimea, there is no reliable information on the content of peptide products [8]regulator.
Semax dosage in studies
Semax has no approved dosage in the EU, because it has no marketing authorisation [7]regulator. Below are the doses used in Russian human studies, taken from the PubMed abstracts. They are not recommendations.
| Study | Who | Dose and route | Duration |
|---|---|---|---|
| Acute stroke (1997) | 30 patients, on top of usual care | Daily doses judged most effective: 12 mg (moderate) and 18 mg (severe); route not stated in the abstract | 5 or 10 days [2]B |
| Peptic ulcer (2002) | patients with hard-to-heal ulcers, on top of ulcer drugs | 1% solution through the nose, 2-4 drops 3 times a day | 10 days [10]B |
| Motor neuron disease (2007) | 27 patients, open-label | 12 mg a day through the nose (1% solution) | two 10-day courses with a 2-week break [11]B |
| Rehabilitation after stroke (2018) | 110 patients, some of whom received Semax | 6,000 µg a day; route not stated in the abstract | two 10-day courses with a 20-day break [3]B |
The developers' overview also mentions doses of 0.015 to 0.050 mg per kg given through the nose, in both experimental animals and humans [1].
What the figures do not tell you
- Semax was always given on top of other treatment, so the effect of the dose itself cannot be separated [2, 3, 10]B.
- The abstracts of the stroke studies do not say whether Semax was given through the nose or by injection [2, 3]B.
- In the peptic ulcer study the dose was given as drops of a 1% solution, not in milligrams [10]B.
- These are doses given to sick patients under medical supervision. They do not tell what dose would be safe or effective for anyone.
The doses as a table with sources: Semax doses in studies. The calculator does not open with Semax preselected, because in the studies the substance was given through the nose or the route is not stated. The general calculator's list includes Semax only to fill in a vial size.
Semax vs Selank: what is the difference?
They are different substances, but they are often sold side by side. Both were found among seized products analysed by a Belgian official laboratory [6]D.
- Semax: a peptide based on the 4-10 segment of ACTH, studied mainly in connection with stroke [1] [2, 3]B.
- Selank: a different peptide, studied for anxiety. More: Selank: research and side effects.
- In common: neither has a marketing authorisation in the EU [7]regulator, and to the laboratory researchers' knowledge neither had completed clinical trials [6]D.
Is Semax legal in Finland?
Semax has no marketing authorisation [7]regulator. Annex 1 A of the Finnish medicines list names its modified form N-acetyl-semax, but not plain Semax [9]regulator.
- Medicines list. Annex 1 A of the Finnish medicines list (230/2025), which covers medicinal substance analogues and prohormones classified as medicines, names N-acetyl-semax [9]regulator. Annex 1 A substances are controlled as medicines in Finland and are always treated like prescription-only medicines. Plain Semax is not named in the list.
- Marketing authorisation. Semax does not appear in the EMA medicines data file generated on 15 Sep 2026 [7]regulator.
- Fimea warning, 29 June 2026. Fimea warned about injectable peptides bought online and sold as "for research use only". According to Fimea, that label means the product is not intended for humans [8]regulator.
- Imports. Ordering medicines from outside the EU is covered on Peptides and the law in Finland. Bringing them from travel: Travelling with peptides.
This is not legal advice. Disclaimer.
How is a Semax product assessed?
You cannot be sure of the content of a Semax product. According to Fimea, there is no reliable information on the content, quality and safety of products sold as peptides [8]regulator. According to the Belgian laboratory, such peptides are freely sold online as powder for injection or as nasal sprays [6]D.
The laboratory had to develop its own method to identify such peptides in seized products [6]D. A seller's own certificate of analysis (COA) does not by itself prove the content or safety. For a certificate even to describe the content, it should identify the substance by mass spectrometry (MS), state the amount and purity, and cover the same batch as the vial. More: How to read a COA and check a test result. Handling: Mixing and handling.
FAQ
Semax: what is it?
A synthetic peptide based on the 4-10 segment of the hormone ACTH, studied mainly in Russian studies [1] [2]B.
Is Semax an approved medicine in the EU?
No. It has no marketing authorisation in the EU [7]regulator. According to a 2026 review, it has been used in Russia for decades [13].
What has Semax been studied for?
Mainly stroke and cerebrovascular insufficiency, in Russian studies [2, 3, 5]B, and in small studies of peptic ulcer and motor neuron disease [10, 11]B.
Does Semax improve memory?
Not known. The developers' overview claims so [1], but no independent randomised memory trials have been published [13].
Semax side effects: what is known?
Little. Investigators have described it as well tolerated without figures [5]B, and in one follow-up study the EEG showed paroxysmal activity after injection [12]B.
Semax dosage: what did studies use?
In Russian studies the daily doses were 6 to 18 mg [2, 3, 11]B, in stroke on top of other treatment [2, 3]B. They are not recommendations: Semax dosage in studies.
Semax in Finland: is it legal?
Semax has no marketing authorisation, and the medicines list names N-acetyl-semax [7, 9]regulator. Fimea warns against injectable peptides bought online [8]regulator. This is not legal advice.
What do users themselves report about Semax?
In the Reddit accounts of 72 people we compiled (not research), 38 (53%) reported some benefit and 27 (38%) some harm. The accounts are self-selected and prove neither that it works nor that it is safe: Semax user experiences.
Read the research yourself: sources
Every source opens the original publication or the regulator's page. The level shows what the source itself reports.
- Ashmarin IP, et al. A nootropic adrenocorticotropin analog 4-10-semax (15 years experience in its design and study). Zh Vyssh Nerv Deiat Im I P Pavlova. 1997;47:420-430. (In Russian.) PMID 9173745 (review)
- Gusev EI, et al. Effectiveness of semax in acute period of hemispheric ischemic stroke (a clinical and electrophysiological study). Zh Nevrol Psikhiatr Im S S Korsakova. 1997;97:26-34. (In Russian.) PMID 11517472 B
- Gusev EI, et al. The efficacy of semax in the treatment of patients at different stages of ischemic stroke. Zh Nevrol Psikhiatr Im S S Korsakova. 2018;118:61-68. (In Russian.) PMID 29798983 B
- Lebedeva IS, et al. Effects of Semax on the default mode network of the brain. Bull Exp Biol Med. 2018;165:653-656. PMID 30225715 B
- Gusev EI, et al. Semax in prevention of disease progress and development of exacerbations in patients with cerebrovascular insufficiency. Zh Nevrol Psikhiatr Im S S Korsakova. 2005;105:35-40. (In Russian.) PMID 15792140 B
- Vanhee C, et al. The occurrence of putative cognitive enhancing research peptides in seized pharmaceutical preparations: an incentive for controlling agencies to prepare for future encounters of the kind. Drug Test Anal. 2020;12:371-381. PMID 31667971 D
- European Medicines Agency. Medicine data (human medicines, data set of 15 Sep 2026): Semax not listed. EMA regulator
- Fimea. Fimea varoittaa: älä käytä verkosta ostettuja pistettäviä peptidejä / Fimea warns: do not use injectable peptides purchased online. 29 Jun 2026. Fimea regulator
- Finland. Lääkeluettelo (Fimea medicines list), 230/2025, annex 1 A. Finlex regulator
- Ivanikov IO, Brekhova ME, Samonina GE, et al. Therapy of peptic ulcer with semax peptide. Bull Exp Biol Med. 2002;134(1):73-74. PMID 12459874 B
- Serdiuk AV, Levitskii GN, Miasoedov NF, et al. The study of chronic partial denervation and quality of life in patients with motor neuron disease treated with semax. Zh Nevrol Psikhiatr Im S S Korsakova. 2007;107(4):29-39. (In Russian.) PMID 18379501 B
- Alekseeva GV, Bottaev NA, Goroshkova VV. Use of semax at a follow-up of patients with posthypoxic encephalopathy. Anesteziol Reanimatol. 1999;(1):40-43. (In Russian.) PMID 10199046 B
- Mavrych V, Shypilova I, Bolgova O. Therapeutic peptides in gerontology: mechanisms and applications for healthy aging. Front Aging. 2026;7:1790247. PMID 42021992 (review)
Research sources checked 9-13 Oct 2026. Regulator and registry sources checked 15 Sep 2026.
Evidence levels: A = randomised human trial or meta-analysis · B = observational human study or case series · C = animal study · D = cell or laboratory study · E = not peer-reviewed · regulator = a regulator's assessment or decision, not research evidence. The marker official means official product information (summary of product characteristics or label); it is not research evidence. For a review, the level shows what kind of research the statement rests on. No level: statements that something has not been studied, reviews' interpretations, named hypotheses and the general rules in our certificate-of-analysis guide.
Content is general information about research, not medical advice. If you have symptoms, contact a healthcare professional.