Semax is a 7-amino-acid peptide developed at the Institute of Molecular Genetics in Moscow and prescribed in Russia as nasal drops for stroke, cognitive problems and optic nerve disease.[1][2][6] In rats it raises the brain growth factor BDNF,[7] but human studies are small, Russian and mostly open-label.[11][12][14] It is not FDA-approved.[3]
What is Semax?
Semax (Met-Glu-His-Phe-Pro-Gly-Pro) is built from a short piece of the hormone ACTH with a stabilizing Pro-Gly-Pro tail added. It is often called an ACTH(4-10) analog, but the Russian label says it has no hormonal activity.[1][6] Its developers described about 15 years of design work by 1997.[26]
How Semax works
Most mechanism data come from animal and lab studies:
- BDNF: a single nasal dose in rats raised hippocampal BDNF 1.4-fold and activated its TrkB receptor,[7] and raised BDNF in the basal forebrain.[8]
- Dopamine and serotonin: Semax increased serotonin turnover and boosted amphetamine-driven dopamine release in rodents.[9]
- Stroke models: it changed the activity of immune and blood-vessel genes after brain ischemia in rats.[10]
- Brain entry: in rats, it reached the brain within minutes of nasal dosing and was rapidly broken down.[25]
FDA describes its mechanism as poorly understood.[3]
Semax benefits: what human research shows
| Use | Study | Result |
|---|---|---|
| Acute stroke | 30 Semax vs 80 standard therapy, not randomized | Some acceleration of recovery, especially motor deficits[11] |
| Stroke rehab | 110 patients, open study | Higher BDNF, better daily-living scores[12] |
| Cerebrovascular disease | 187 patients | Authors report fewer strokes and TIAs[13] |
| ALS | 27 patients, open study | No effect on disease scales; better quality-of-life score[14] |
| Optic nerve disease | Controlled study | Better visual acuity and fields[15] |
| Healthy volunteers | 24 people, placebo-controlled | Changes in resting brain networks on fMRI[17] |
| Healthy volunteers | 52 people (Semax, Selank or placebo) | Changes in brain network activity[18] |
A closer look at the stroke and brain studies
- Acute stroke (1997): 30 patients got Semax on top of usual care and were compared with 80 similar patients on usual care alone. The authors reported faster recovery of general and motor symptoms. They judged 12 mg a day best for moderate strokes and 18 mg a day for severe strokes, over 5 to 10 days.[11]
- Stroke rehabilitation (2018): 110 adults with an average age of 58 started rehab either about 3 months or about 7 months after their stroke. Some got two 10-day courses of 6,000 mcg a day, 20 days apart. Semax raised blood BDNF and sped up recovery of daily activities, with a smaller effect on weakness.[12]
- ALS (2007): 27 patients took 12 mg a day in two 10-day courses. Nerve tests and disease scores did not change, but quality of life, mood and motivation improved, peaking around day 10.[14]
- Brain injury after oxygen loss (1999): in 73 patients, Semax helped memory problems, but some had abnormal EEG activity after a dose.[16]
- Brain scans (2018): 14 healthy volunteers took 1% Semax and 10 took placebo. Scans 5 and 20 minutes later showed a larger frontal part of the brain’s resting “default mode” network with Semax.[17]
We found no Semax trials registered on ClinicalTrials.gov, the main public trial registry.[29] None of the studies above was a large, randomized, double-blind trial with long follow-up.
Semax dosage
The Russian label doses Semax by drops. One drop of 0.1% contains 50 mcg; one drop of 1% contains 500 mcg.[1][2]
| Use (Russian label) | Dose | Course |
|---|---|---|
| Cognitive and vascular disorders (0.1%) | 2 to 3 drops per nostril, up to 4 times daily (800 to 8,000 mcg/day) | 10 to 14 days[1] |
| Mental fatigue and adaptation (0.1%) | 2 to 3 drops per nostril, 2 to 3 times daily (400 to 900 mcg/day) | 3 to 5 days[1] |
| Children 7 and older (0.1%) | 1 to 2 drops per nostril twice daily | 30 days[1] |
| Moderate ischemic stroke (1%) | 6,000 to 12,000 mcg/day | 10 days[2] |
| Severe ischemic stroke (1%) | 12,000 to 20,000 mcg/day | 10 days[2] |
FDA found no safety data for injected Semax, although injectable forms are sold online.[3] To convert milligrams to drops or syringe units, see our peptide calculator.
Semax 0.1% vs 1%
| Semax 0.1% | Semax 1% | |
|---|---|---|
| Strength per drop | 50 mcg[1] | 500 mcg[2] |
| Main uses | Cognitive problems, recovery after brain injury, mental fatigue, optic nerve disease, children 7 and older[1] | Acute ischemic stroke only[2] |
| Age limit | 7 and older (18 and older for eye and post-neurosurgery use)[1] | 18 and older[2] |
Semax for ADHD, anxiety and depression
- ADHD: the Russian 0.1% label includes children aged 7 and older with minimal brain dysfunction, including ADHD.[1] We found no randomized trials of Semax in ADHD.
- Anxiety: the label lists disorders accompanied by anxiety as a contraindication,[1] and some users report anxiety or irritability at higher doses.[24]
- Depression: in rats under chronic stress, Semax had antidepressant-like effects.[27] It has not been tested for depression in people.
How long does Semax last?
No human half-life has been published.[3] In rats, Semax reached the brain within minutes of nasal dosing and was quickly broken down,[25] and its Pro-Gly-Pro tail on its own did not protect the brain in a rat model of global cerebral ischemia.[28] Forum users describe alertness lasting roughly 4 to 9 hours after a dose.[24]
Semax side effects
- Label: mild nasal irritation with prolonged use is the only listed side effect.[1]
- Contraindications: acute psychiatric conditions, disorders with anxiety, a history of seizures, pregnancy and breastfeeding, and children under 7 (0.1%; under 18 for eye and neurosurgical use) or under 18 (1%).[1][2]
- EEG changes: a 1999 study saw abnormal EEG activity in some patients after dosing and advised EEG monitoring.[16]
- FDA concerns: possible bleeding risk, immune reactions to injected product, impurities, and abuse potential based on the dopamine findings. FDA also logged a report of eye pain after using Semax bought online.[3]
- Tolerability in older adults: the authors of the 187-patient cerebrovascular study described few side effects, including in older patients.[13]
Questions to ask your clinician
- Is there an approved treatment with stronger evidence for my problem, such as stroke rehabilitation or an ADHD medicine?
- Do I have anything on the label’s do-not-use list, such as anxiety, seizures or pregnancy?[1]
- How would we judge whether it helps, and when should I stop?
Semax vs Selank
| Semax | Selank | |
|---|---|---|
| Based on | ACTH fragment | Tuftsin (immune peptide) |
| Russian use | Stroke and cognition (prescription)[1] | Anxiety (over the counter) |
| Typical effect reported | Stimulating, focus | Calming |
Both add the same stabilizing Pro-Gly-Pro tail to a natural peptide fragment.[6] Read our full Selank profile for its anxiety research.
N-Acetyl Semax Amidate
This modified form is sold by research-chemical vendors. There are no human studies of it, and a lab study found that N-terminal acetylation (without amidation) removed Semax’s protection against copper toxicity in neuroblastoma cells.[19] Belgian authorities have found Semax in seized products.[20]
Is Semax legal?
- Russia: prescription drug; both the 0.1% and 1% forms are on the essential medicines list.[1][2]
- US: not FDA-approved. Semax was nominated for compounding and withdrawn,[4] then FDA evaluated it in 2026. Staff recommended against listing it, but the advisory committee reportedly voted 8 to 5 in favor.[3][5] FDA has not issued a final decision.
- Sports: not named on WADA’s 2026 list, but its status is ambiguous.[21]
This is general information, not legal advice.
