Seven-amino-acid analog of an ACTH fragment, sold as Russian nasal drops for stroke and memory problems; not approved in the US.
Also called ACTH(4-10) analog, ACTH(4-7)-Pro-Gly-Pro, Met-Glu-His-Phe-Pro-Gly-Pro, Semax 0.1%, Semax 1%
Semax is a short synthetic peptide built from the first four amino acids of ACTH's 4-10 fragment (Met-Glu-His-Phe) with Pro-Gly-Pro added on the end so blood enzymes do not chew it up in seconds. It was developed in Moscow at the Institute of Molecular Genetics and is a registered prescription drug in Russia as 0.1% and 1% nasal drops. The 0.1% drops are labeled for memory and attention problems after vascular brain injury, optic nerve disease and, in children over 5, minimal brain dysfunction; the 1% drops are labeled for acute ischemic stroke.
In rats, intranasal Semax raises BDNF protein in the basal forebrain within 3 hours and shifts hundreds of genes tied to inflammation and blood vessels after an experimental stroke. In people, the evidence is a set of Russian clinical studies: stroke patients given Semax on top of standard care recovered motor function somewhat faster, and a 2018 study of 110 stroke survivors found higher blood BDNF and better Barthel scores in the Semax groups. None of these trials was a large, blinded, randomized trial with a hard outcome like disability at 90 days.
Online, Semax is sold as a focus and memory peptide for healthy people. That use has almost no human data behind it: two small placebo-controlled brain-imaging studies show it changes resting brain network activity within 20 minutes, which is not the same as showing it improves memory or work output. FDA reviewed Semax for compounding in 2026. Its staff concluded the evidence weighed against allowing it, but the outside advisory committee voted 8-5 in favor, according to trade press coverage. FDA has not made a final decision.
What it binds to, and what happens inside the body after that, step by step.
Semax does not stimulate the adrenal glands the way full ACTH does. In rodent brain tissue it binds a specific, still unidentified site in the basal forebrain and raises BDNF and its receptor TrkB. It also slows the enzymes that break down enkephalins and, after experimental stroke, changes the expression of immune and blood-vessel genes. How much of this happens at the doses people use is not known.
Human results and animal results are kept apart below. A result in rats tells you a mechanism is plausible. It does not tell you what happens in a person.
Human evidence is limited to Russian clinical studies, mostly in stroke, cerebrovascular disease and optic nerve disease, with comparison groups that were not blinded or clearly randomized. The strongest signal is faster motor recovery and higher BDNF in stroke patients given Semax on top of standard care. There are no Western randomized trials and no trials showing cognitive benefit in healthy people; the brain-boosting claims online rest on rat data and two small brain-scan studies.
110 adults after ischemic stroke, early vs late rehabilitation, with and without Semax
Two 10-day courses of Semax raised plasma BDNF and were linked to faster and better Barthel index recovery; the effect on paresis was smaller. Groups were not described as randomized or blinded.
Read the study30 acute stroke patients on Semax vs 80 matched controls on standard care
Adding Semax sped regression of general and focal, especially motor, deficits; the authors reported the best results with higher daily doses in more severe strokes.
Read the study24 healthy volunteers, 14 given 1% Semax and 10 given placebo
Resting-state fMRI 5 and 20 minutes after a dose showed a larger frontal default-mode network component in the Semax group; no cognitive outcome was measured.
Read the study187 patients with chronic cerebrovascular insufficiency
Authors reported clinical improvement and fewer strokes and transient ischemic attacks with few side effects; the abstract gives no effect sizes.
Read the study27 patients with motor neuron disease (ALS spectrum)
Semax did not change muscle denervation or functional decline, but quality-of-life scores improved, peaking at day 10.
Read the studyPatients with vascular, toxic or inflammatory optic nerve disease, Semax drops or electrophoresis vs control
Adding Semax was reported to speed recovery of visual acuity, visual field and color vision; numbers are not given in the abstract.
Read the studyRats, intranasal dosing and brain membrane binding assays
Intranasal Semax at 50 and 250 mcg/kg raised basal forebrain BDNF within 3 hours and bound a specific site with a KD of about 2.4 nM.
Read the studyThese are questions the published research has not answered.
Not FDA- or EMA-approved. Both strengths are prescription-only in Russia and are on Russia's list of vital and essential medicines. Year for the 1% drops is taken from its original registration number (P N000812/01); the original registration year for the 0.1% drops is not verified, so the year shown is when the current label text was agreed (2008). Secondary sources place first registration in the mid-1990s. Semax is not named on the 2026 WADA Prohibited List. It is an ACTH fragment analog but has no cortisol-releasing activity, so WADA's corticotrophin class (S2.2.2) does not obviously cover it; because it is a government-approved drug in Russia it does not clearly fall under WADA's S0 category for unapproved substances, but athletes should confirm with their anti-doping authority before using any unlisted peptide.
No human half-life has been published for Semax, so we do not draw a clearance curve. Half-lives quoted online for it are usually estimates from animal data.
This table records the doses that trials and approved labels used, with the source for each row. It is a record of research, not a recommendation, and it is open to free members.
Which symptoms are expected and which mean stop and get help: side effects and red flags.
Tap a claim to see what the studies found.
No published randomized trial in healthy adults measures memory or performance. The human brain-scan studies show network changes, not better test scores.
Shown in rat brain tissue. In people, only plasma BDNF has been measured, in stroke patients, and plasma BDNF does not tell you what is happening in the brain.
It is registered in Russia, but the approval rests on small domestic studies, and FDA found no human pharmacokinetic or injectable safety data in 2026.
The Russian 0.1% label lists minimal brain dysfunction in children 5 and older, including ADHD, but FDA's 2026 review found no supporting clinical literature for ADHD. The English-language ADHD literature is a hypothesis paper, not a trial.
The approved form is intranasal. There are no human data on subcutaneous Semax.
These pairings come up often. Almost none have been tested together in a trial, and the evidence note on each says so plainly.
Research material is shipped as powder; FDA notes the substance is expected to be stable below -20 C. Keep frozen and dry.
The registered drops come as a ready solution with a preservative; the Russian label says to store them protected from light at no more than 10 C and not to freeze them. For reconstituted research peptide, no published stability data exist.
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