Semax

Origin and structure

Semax is a chain of seven amino acids, Met-Glu-His-Phe-Pro-Gly-Pro (C37H51N9O10S, 813.9 g/mol, CAS 80714-61-0). The first four are positions 4 to 7 of adrenocorticotropic hormone (ACTH), the pituitary hormone that drives cortisol release. The natural fragment ACTH(4-10) continues with Arg-Trp-Gly; Semax replaces those three with the tripeptide Pro-Gly-Pro, which is thought to make the chain more resistant to enzymes that cut peptides. Fragments from this part of ACTH lack the hormone's effects on the adrenal glands and on pigment cells, but in animals they keep effects on behaviour and learning, which is what the developers set out to use.

The peptide was developed at the Institute of Molecular Genetics of the Russian Academy of Sciences in Moscow, under the academicians Igor Ashmarin and Nikolai Myasoedov; a method for making it was published in 1984. 'Semax' is a common name rather than an official US drug name, and in 2026 the FDA noted that products sold under it may contain the free peptide or its acetate salt (C39H55N9O12S, 874.0 g/mol) without saying which. Variants sold online as N-acetyl Semax or N-acetyl Semax amidate are different molecules; the studies described on this page were not done with them.

How it is thought to work

No receptor for Semax has been established, and in 2026 the FDA described its mechanisms as poorly understood. Nearly all the mechanistic work comes from the developers' institute and allied Moscow laboratories and was done in rats and mice. After a single nasal dose of 50 µg per kg, the activity of the genes for the nerve growth factors BDNF and NGF in the rat hippocampus had risen an hour later. In rats with an experimental stroke, infarcts were about 20% smaller with nasal Semax than with a dummy treatment in one model, and in another it damped the switching-on of inflammation genes. In rodents it raised the level of the serotonin breakdown product 5-HIAA in the striatum and amplified the dopamine release caused by amphetamine.

Semax also affects blood clotting in rats: five days of nasal Semax raised the blood's capacity to dissolve clots and led to smaller clots in a clamped vein, and another study found about 35% less platelet aggregation, possibly through its breakdown product Pro-Gly-Pro. In the test tube it slows the enzymes that break down enkephalins, the body's own opioids.

How Semax behaves in people has not been measured: the FDA found no human pharmacokinetic study by any route. In rats it is broken down quickly in the blood, mainly into Pro-Gly-Pro. After a nasal dose, about 0.07% of a radioactively labelled dose reached the rat brain, against about 0.005% after an injection into a vein, which fits with giving it through the nose.

Is Semax approved?

In Russia, yes. Semax is one of the peptide medicines registered in the Russian Federation, classed there as a nootropic and available as nasal drops of 0.1% and 1%; it is used there to treat ischaemic stroke, among other brain disorders. That is a national Russian registration; it does not count as an approval in the EU or the US.

No medicine containing Semax is authorised by the EMA, and it is not a registered medicine in the Netherlands, so it may not be sold or promoted there for use in people; it is available only as research material, which is the basis our shop operates on.

In the United States Semax is not approved for any use. Two nominators, Wells Pharmacy Network and LDT Health Solutions, proposed it for the list of bulk substances that pharmacies may compound with and later withdrew; the FDA reviewed it anyway. Its staff evaluation, dated 11 May 2026, looked at cerebral ischaemia, migraine and trigeminal neuralgia and recommended against adding Semax or Semax acetate: the substance was poorly characterised, the evidence of effectiveness was insufficient, there was a possible bleeding risk, and the risk of immune reactions was unknown. On 24 July 2026 the FDA's Pharmacy Compounding Advisory Committee nevertheless voted 8 to 5, with one abstention, to recommend it. The vote does not bind the FDA, and by 28 October 2026 no rule adding Semax to the list had been published.

In sport Semax is not named on the 2026 WADA Prohibited List. Category S0 bans any substance without a current approval by a government health authority for human therapeutic use, but Semax is registered in Russia, so S0 does not plainly apply; category S2 bans corticotrophins such as tetracosactide, but Semax lacks ACTH's hormonal action on the adrenal glands. We found no WADA ruling on Semax. Athletes in the Netherlands can put the question to the Dopingautoriteit, which applies the WADA list.

What the research shows

Almost all clinical work on Semax was done in Russia, much of it published in Russian with only an English abstract, and ClinicalTrials.gov lists no Semax trial. The FDA, which considered only reports available in English, counted 33 to 47 healthy adults, 69 adults with illnesses and 451 children who had received Semax in the studies it could assess, and set aside the Russian-language stroke studies because no full translation was available. The main findings:

• Acute stroke (Gusev et al., 1997): 30 patients with an ischaemic stroke in one hemisphere received Semax nasal drops on top of standard treatment and were compared with 80 patients with strokes of similar severity and location on standard treatment alone. The authors reported that general and focal deficits, motor deficits in particular, receded somewhat faster with Semax. The abstract does not describe randomisation or blinding.
• Stroke rehabilitation (Gusev et al., 2018): 110 patients about three or about seven months after an ischaemic stroke were divided into groups with and without Semax. With Semax, blood levels of BDNF rose and stayed high during the study, and scores on the Barthel index of daily activities improved faster. The abstract does not say how patients were assigned to Semax.
• Chronic cerebrovascular disease (Gusev et al., 2005): in 187 patients with cerebrovascular insufficiency the authors reported clinical improvement, slower progression and fewer strokes and transient ischaemic attacks with Semax, and few side effects; the abstract gives no figures and does not describe the comparison group.
• Head injury (Indharty, 2013): the only full clinical paper from outside Russia that we found. In Medan, Indonesia, 40 patients with a moderate head injury received standard care with or without five days of Semax nasal drops; the methods call the allocation random, and there was no placebo. Serum Bcl-2, a protein that protects cells from programmed death, rose with Semax but not with standard care alone, and hospital stays were shorter. The paper gives different Bcl-2 figures in different places.
• Healthy volunteers: a 1996 study in 19 healthy men reported 'nootropic-like' effects. In a 2018 brain-imaging study, 24 healthy adults were scanned before and 5 and 20 minutes after 1% Semax (14 people) or placebo (10 people) in the nose; one part of the brain's resting-state network was larger in the Semax group (Lebedeva et al.).
• Pain (Koroleva et al., 1996, as summarised by the FDA): after a single nasal dose, 4 of 12 people with migraine said their headache stopped within 90 to 120 minutes, and in 16 people with typical trigeminal neuralgia nothing changed. The study had no control group and no blinding, and the authors concluded that Semax has no pain-relieving effect of its own.
• Peptic ulcer (Ivanikov et al., 2002): in 32 patients with ulcers that had resisted treatment, ulcers had healed by day 14 in 89.5% of those given Semax drops alongside standard drugs, against 30.8% on standard drugs alone.
• Motor neuron disease (Serdiuk et al., 2007): in an open-label study of 27 patients, two 10-day courses changed neither the nerve-muscle measurements nor the functional scores, but quality-of-life scores improved, mainly through mood and motivation, with the largest effect on day 10.
• Children: two conference abstracts describe Semax given alongside other treatments to 120 adolescents with depression and 331 children with tics or Tourette syndrome; the FDA could find no full reports and no safety data from them.

Side effects and safety

Human safety data for Semax are thin. Most published studies did not report on side effects at all; the small pain study recorded none, and the 2005 study in 187 patients described few side effects without giving numbers. The FDA concluded in 2026 that there is not enough clinical information to characterise its safety, that no human pharmacokinetic studies exist, and that there are no human data at all for injection under the skin, one of the routes proposed for compounding.

The specific concerns come from animal studies and single reports. Because Semax reduced clotting and platelet aggregation in rats, the FDA flagged a possible bleeding risk, especially for people prone to bleeding or taking other drugs that raise bleeding risk. Its boost of amphetamine-induced dopamine release in rodents raises the question of abuse potential, which has never been tested. In a Russian study of 73 patients with brain damage after oxygen deprivation, some showed episodes of paroxysmal EEG activity after Semax, and the authors advised monitoring brain activity at the first dose. The FDA's adverse-event database held one report up to December 2025: a woman who had eye pain and burning, with a hospital admission, after using Semax 0.1% nasal drops bought online; a year later the pain had not resolved.

The usual animal safety package is missing: the FDA found no acute, repeat-dose, genetic-toxicity or reproductive-toxicity studies and no adequate long-term cancer study. It also warned that peptides of this kind can clump together and trigger immune reactions, and the certificates of analysis for bulk Semax it reviewed did not test for such aggregates, microbes or bacterial endotoxins.

Semax versus Selank

Selank is a related Russian peptide that is also registered in Russia. It has the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro: the same Pro-Gly-Pro tail, but attached to tuftsin (Thr-Lys-Pro-Arg), a small peptide with effects on the immune system, instead of to a fragment of ACTH. Russia classes Selank as an anxiolytic, a medicine against anxiety, and Semax as a nootropic.

The two are often sold together and combined, but they start from different natural peptides and are claimed to do different things, and no trial has compared them for a clinical outcome or tested the combination. Evidence for one says nothing about the other.

Frequently asked questions

Is Semax legal in the Netherlands?

Semax is not a registered medicine in the Netherlands or anywhere else in the EU, and its Russian registration does not count here, so it may not be sold, advertised or supplied for use in people. Buying and selling it as research material is a different status, which our guide on research-use-only products in the Netherlands explains.

Is Semax an approved medicine anywhere?

In Russia, where it is registered as 0.1% and 1% nasal drops. The EMA and the FDA have never approved it. In the US, FDA staff advised against letting pharmacies compound it, but in July 2026 an FDA advisory committee voted 8 to 5 in favour; by 28 October 2026 the FDA had not made that a rule.

Does Semax increase BDNF?

In rats, yes: a single nasal dose raised the activity of the BDNF gene in the hippocampus within an hour. In people, the main evidence is one Russian study in 110 stroke patients, in which blood levels of BDNF rose with Semax and stayed high. That has not been shown to translate into better memory or focus in healthy people.

What is the difference between Semax and Selank?

Both are Russian peptides with a Pro-Gly-Pro tail and both are registered in Russia, but they are different molecules. Semax is built on a fragment of the hormone ACTH and is classed as a nootropic; Selank is built on tuftsin and is classed as an anxiolytic. No trial has compared them on a clinical outcome or tested them together.

Is N-acetyl Semax the same as Semax?

No. N-acetyl Semax and N-acetyl Semax amidate are chemically modified versions, not the peptide that is registered in Russia. The studies on this page were done with Semax itself, and we found no published study showing that the variants are several times stronger, as online sellers claim, so that claim is unsupported.

Is Semax banned in sport?

It is not named on the 2026 WADA Prohibited List. Unnamed substances without any government approval for human use fall under category S0 and are banned at all times, but Semax is registered in Russia, so it is not clear that S0 applies, and we found no WADA ruling on it. Athletes in the Netherlands can check with the Dopingautoriteit.

Storage and handling

Store according to product-label instructions and batch handling notes. Lyophilized research peptides are commonly kept dry, protected from light, and handled with clean laboratory technique.

References

Checked against these sources on 28 October 2026.

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