Cerebrolysin vs Semax
Last updated: October 3, 2026 · 5 min read · By the Grey Peptides Editorial Board
- Cerebrolysin is a pig-brain peptide mixture given by intravenous infusion; semax is a single synthetic peptide given as nasal drops.
- Cerebrolysin has far more trials, but the Cochrane review found it does not reduce deaths after stroke and may increase non-fatal serious adverse events. Semax's stroke studies are small and mostly open-label.
- Neither is approved in the US, and neither has been tested as a brain booster in healthy people.
Side by side
Cerebrolysin High and semax Medium share a use, stroke, and a market, online nootropic sellers. Almost everything else differs 1. The table is read from our encyclopedia entries.
| Field | Cerebrolysin | Semax |
|---|---|---|
| Encyclopedia entry | Cerebrolysin Full entry | Semax Full entry |
| Molecule class | Blend or mixture | Peptide |
| Category | Cognitive | Cognitive |
| FDA status | Not FDA Approved | Not FDA Approved |
| Approved elsewhere | Austria and ~50 other countries | Russia |
| Evidence grade | High | Medium |
| Half-life | Varies by component | Not measured in humans |
| Formula | Not stated | C37H51N9O10S |
| Molecular weight | Not stated | 813.9 g/mol |
| WADA 2026 | Unsettled (S0 may apply) | Unsettled (S0 may apply) |
| WADA 2027 | Unsettled (S0 may apply) | Unsettled (S0 may apply) |
| In one line | A pig-brain peptide mixture approved in about 50 countries for stroke and dementia; Cochrane found no survival benefit after stroke and more non-fatal serious adverse events. | A synthetic ACTH-derived heptapeptide approved in Russia for stroke rehabilitation and optic nerve disorders, with documented BDNF upregulation and broad nootropic activity. |
| Mechanism | Multiple neurotrophic and neuroprotective effects: peptide components mimic the action of endogenous neurotrophic factors on TrkA, TrkB, and p75 receptors; amino acid components provide substrate for neurotransmitter synthesis. Demonstrated effects include enhanced synaptic plasticity, reduced excitotoxicity, reduced amyloid-β toxicity, and promotion of neurogenesis in animal models. | In rats, a single dose raised hippocampal BDNF protein 1.4-fold and exon III BDNF mRNA threefold, with more trkB activation, and intranasal doses raised basal-forebrain BDNF within three hours; it binds specific sites there. It increased striatal serotonin turnover and strongly amplified amphetamine's dopamine and locomotor effects. In rat stroke models it shifts immune-response gene expression. How these findings translate to people is not established. |
| Sources in the entry | 12 | 13 |
| Study cards | 12 | 11 |
| Dosage page | None | Dosage page |
Two very different products
Cerebrolysin is a mixture, not a molecule: low-molecular-weight peptides and amino acids from pig brain, given by intravenous infusion and widely used for acute stroke in Russia, Eastern Europe, China and other Asian and post-Soviet countries 2. Semax is a single synthetic seven-amino-acid peptide derived from ACTH, given as nasal drops and approved in Russia, where it is used in stroke and optic-nerve disease 1. One requires a drip in a clinic; the other is a bottle of drops. That difference alone matters for anyone buying either online, because no trial used the routes that online sellers often suggest for cerebrolysin.
Stroke: the evidence for each
Cerebrolysin's stroke evidence is the larger and better examined. The 2023 Cochrane review pooled seven randomised trials with 1,773 people: little to no difference in death from any cause (risk ratio 0.96), and more people with non-fatal serious adverse events (risk ratio 2.39), with the risk of bias judged largely unclear and three multicentre trials supported by the manufacturer (moderate-certainty evidence) 2. The largest trial, CASTA, with 1,070 patients, missed its primary outcome 3. Smaller trials of rehabilitation report better arm function and stroke-scale scores 4.
Semax's stroke evidence is small and less rigorous. In 110 patients months after stroke, two ten-day courses raised plasma BDNF and were associated with better recovery measures, without blinding (human study) 5. An older study of 30 acute patients reported 'some influence' on recovery speed against 80 on conventional care 6. No systematic review of semax in stroke appears in what we read.
How each is thought to work
Cerebrolysin is thought to act like a cocktail of growth-factor-like signals; in rats with stroke it increased new nerve cells and reduced cell death (animal evidence) 7. Semax raised BDNF and activated its receptor in rat hippocampus after a single nasal dose (animal evidence) 8, and in rats with stroke it influenced the immune response more than any other process (animal evidence) 9. Neither mechanism has been tied to a clinical benefit in a large trial.
Safety
For cerebrolysin, controlled trials found mostly mild, short-lived effects such as dizziness, agitation and feeling hot 10, but the Cochrane review's signal of more non-fatal serious adverse events is the more important finding 2. For semax, the small studies report few problems, but they were not designed to detect uncommon harms. Both are injected or applied as hospital or pharmacy products where approved; vials sold online for research are neither.
How the differences add up (as of October 3, 2026)
Cerebrolysin has the bigger evidence base, and that evidence is the reason for caution: the most independent review found no survival benefit and a possible increase in serious adverse events. Semax has much less evidence, of lower quality, and no independent review. Neither is FDA-approved, and both have unsettled WADA status, because whether S0 applies depends on how their approvals elsewhere are treated 1. As nootropics for healthy people, neither has been tested. Our cerebrolysin evidence guide and semax vs selank comparison go further. Doses on this page are those in our entries' sources, not recommendations.
Frequently asked questions
What is the difference between cerebrolysin and semax?
Cerebrolysin is a pig-brain peptide mixture given by intravenous infusion; semax is a single synthetic ACTH fragment given as nasal drops. Both are used after stroke in parts of Europe and Asia.
Which has better evidence for stroke?
Cerebrolysin has more trials, but the Cochrane review found no reduction in deaths and more non-fatal serious adverse events. Semax's stroke studies are small and mostly open-label.
Can either be used as a nootropic?
Neither has been tested for memory or focus in healthy people.
Related on Grey Peptides
Sources
- Grey Peptides dataset records for cerebrolysin and semax (where each is used, FDA status, WADA status unsettled, studied doses as sourced on each entry); read October 3, 2026.
- Ziganshina, L. E., et al. (2023). Cerebrolysin for acute ischaemic stroke. Cochrane Database Syst Rev, 10(10), CD007026. PMID: 37818733
- Heiss, W. D., et al. (2012). Cerebrolysin in patients with acute ischemic stroke in Asia: results of a double-blind, placebo-controlled randomized trial. Stroke, 43(3), 630-6. PMID: 22282884
- Muresanu, D. F., et al. (2016). Cerebrolysin and Recovery After Stroke (CARS): A Randomized, Placebo-Controlled, Double-Blind, Multicenter Trial. Stroke, 47(1), 151-9. PMID: 26564102
- Gusev, E. I., et al. (2018). [The efficacy of semax in the tretament of patients at different stages of ischemic stroke]. Zh Nevrol Psikhiatr Im S S Korsakova, 118(3. Vyp. 2), 61-68. PMID: 29798983
- Gusev, E. I., et al. (1997). [Effectiveness of semax in acute period of hemispheric ischemic stroke (a clinical and electrophysiological study)]. Zh Nevrol Psikhiatr Im S S Korsakova, 97(6), 26-34. PMID: 11517472
- Zhang, C., et al. (2010). Cerebrolysin enhances neurogenesis in the ischemic brain and improves functional outcome after stroke. J Neurosci Res, 88(15), 3275-81. PMID: 20857512
- Dolotov, O. V., et al. (2006). Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus. Brain Res, 1117(1), 54-60. PMID: 16996037
- Medvedeva, E. V., et al. (2017). Semax, an analog of ACTH((4-7)), regulates expression of immune response genes during ischemic brain injury in rats. Mol Genet Genomics, 292(3), 635-653. PMID: 28255762
- Thome, J., et al. (2012). Safety profile of Cerebrolysin: clinical experience from dementia and stroke trials. Drugs Today (Barc), 48 Suppl A, 63-9. PMID: 22514795
Educational information, not medical advice. Each dose in this guide names its source, an approved label or a published study. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose.
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