Semax vs Selank: how the two Russian peptides differ

The two peptides look alike on paper and are different in purpose. Semax was built from a fragment of the stress hormone ACTH and is sold in Russia as a nootropic for memory and attention problems after stroke, head injury or other brain damage. Selank was built from tuftsin, a small fragment of an antibody, and is sold in Russia as an anxiolytic, a drug for anxiety and tension ^[4][9].

That split shows up everywhere else. Semax’s human studies are in stroke patients, Selank’s are in people with anxiety disorders, and the Russian Semax label lists anxiety disorders among its contraindications, the very condition Selank is registered to treat ^[4]. The shared Pro-Gly-Pro tail is the reason they are grouped together, not evidence that they do the same thing.

Neither has been approved by a regulator in the UK, US, Canada, Australia or New Zealand, and neither has been tested in large independent trials. Our individual guides to Semax and Selank cover each one in more depth.

Semax has the sequence Met-Glu-His-Phe-Pro-Gly-Pro. The first four amino acids are positions 4 to 7 of adrenocorticotropic hormone (ACTH), the pituitary hormone that drives cortisol release, and researchers describe the whole molecule as an analogue of ACTH(4-10) ^[1]. The Russian product information states that it is completely lacking in hormonal activity ^[4].

Selank has the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. Its first four amino acids are tuftsin, a peptide cut from the heavy chain of immunoglobulin G that has immune-signalling activity ^[5]. So one peptide descends from a hormone and the other from an immune protein. Both have seven amino acids, both end in Pro-Gly-Pro, and much of the published research on both comes from the Institute of Molecular Genetics of the Russian Academy of Sciences and partner institutes in Moscow.

For Semax the most-cited mechanism is brain-derived neurotrophic factor (BDNF), a protein involved in nerve-cell survival and learning. In rats, tritium-labelled Semax bound specifically to membranes from the basal forebrain, and intranasal doses of 50 and 250 µg/kg quickly raised BDNF levels there ^[1].

For Selank the proposals are different. In blood samples it inhibited enzymes that break down enkephalins, the body’s own opioid peptides, and the authors suggested this could explain its anti-anxiety effect ^[5]. In rats it changed the activity of many genes involved in GABA signalling, the system targeted by benzodiazepines ^[8]. In rats given alcohol long term, Selank prevented alcohol-related changes in BDNF in the hippocampus and frontal cortex ^[22].

There is one overlap. A 2001 laboratory study found that both peptides inhibited enkephalin-degrading enzymes in human serum, with Semax somewhat stronger (half-maximal inhibition at 10 micromolar) than Selank (20 micromolar) ^[10]. All of this is laboratory and animal work from the same Russian research network; none of these mechanisms has been confirmed in human trials.

Semax’s clinical studies are mostly in stroke. A 1997 study gave it to 30 patients in the acute phase of ischaemic stroke and compared them with 80 patients on standard treatment; the authors reported faster neurological recovery, especially of movement ^[2]. A 2018 study of 110 patients in stroke rehabilitation reported higher blood BDNF and better scores for daily living in those given Semax ^[3]. Neither was a large randomised, placebo-controlled trial.

Selank’s clinical studies are in anxiety. In a 2008 randomised study, 62 patients with generalised anxiety disorder or neurasthenia received Selank or the benzodiazepine medazepam, and the authors reported similar anti-anxiety effects ^[6]. A 2014 study in 60 patients compared it with phenazepam and reported pronounced anti-anxiety and mild nootropic effects ^[7], and a 2015 study found that adding Selank to phenazepam reduced some of phenazepam’s side effects ^[21]. A 2008 study in patients with generalised anxiety disorder and neurasthenia also reported shifts in blood cytokines, immune signalling molecules, during 14 days of Selank ^[20].

All of these studies are small, were run by groups involved in developing the drugs, and are published in Russian with short English abstracts. A 2021 US pharmacology review described Selank as poorly studied ^[17]. Claims about focus, memory or mood in healthy people are not supported by controlled evidence for either peptide.

Only in small experiments, not in clinical trials. In a 2020 brain-imaging study, 52 healthy volunteers received Semax, Selank or placebo, and resting-state functional MRI was taken before and 5 and 20 minutes after dosing. The authors reported both shared and peptide-specific changes in connectivity between the right amygdala, a region involved in anxiety, and parts of the temporal cortex ^[11]. The study measured brain signals, not symptoms or performance.

A 2017 rat study gave each peptide to animals with a chemically induced model of Parkinson’s disease. Neither changed motor activity, but Selank reduced anxiety-like behaviour in a maze test ^[12]. These two studies are the closest thing to a semax vs selank comparison in the published literature, and neither says whether Semax or Selank is “better” for any purpose.

The benefits claimed online for the pair, sharper focus from Semax and calm from Selank, map onto the two Russian registrations rather than onto independent trial results. What has been reported is narrower: faster recovery measures after stroke with Semax ^[2][3], and anti-anxiety effects similar to older benzodiazepines with Selank in small studies ^[6][7].

Missing from both evidence bases are placebo-controlled trials of adequate size, trials outside Russia, and trials in healthy people taking the peptides for performance. We found no trials registered or published outside Russia for either one. A 2020 Belgian analysis of seized products noted that both are sold online as powders and nasal sprays, outside any medicines framework ^[15].

Both registered Russian products are nasal drops, not injections. Semax nasal drops are 0.1%, which means 1 g of peptide per litre, or 1 mg per mL, and the label says one drop of the standard solution contains 50 µg ^[4]. A 2018 imaging study used a stronger 1% intranasal Semax solution ^[14]. Selank nasal drops are 0.15%, or 1.5 mg of Selank diacetate per mL ^[9].

The labels report good uptake through the nose. The Semax label says up to 60 to 70% is absorbed from the nasal lining and that it crosses into the brain ^[4]; in rats given a labelled intranasal dose, Semax was detectable in the brain two minutes later ^[13]. The Selank label gives an absolute intranasal bioavailability of 92.8% ^[9].

Products sold as a “semax selank blend” or combined nasal spray by research peptide vendors are not the Russian products and have no registered formulation, strength or stability data. Their contents depend on the seller, which is why a batch certificate matters; see our guide on how to read a peptide COA.

No published source gives a combined dosage chart for the two peptides, and we do not make one. What can be reported is what the Russian labels and the studies used, as information only.

The Semax label gives 50 µg per drop and no more than two to three drops per nostril at a time. For memory and attention problems linked to vascular brain disease, it lists single doses of 200 to 2,000 µg and daily doses of 800 to 8,000 µg, given as two to three drops per nostril four times a day for 10 to 14 days ^[4]. The 1997 acute stroke study reported 12 mg a day for moderate strokes and 18 mg a day for severe strokes, for 5 to 10 days ^[2], and the 2018 rehabilitation study used two 10-day courses of 6 mg a day ^[3].

The Selank label gives no fixed dose and states that dosing is individual, depending on the indication, age and clinical situation ^[9]. The English abstracts of the Selank trials do not report the doses used ^[6][7]. Rat studies of both peptides used doses in µg or mg per kg of body weight, which cannot be converted into human doses.

For converting a percentage solution into micrograms per drop or per mL, the arithmetic is simple: 0.1% is 1 mg per mL and 0.15% is 1.5 mg per mL. Our peptide calculator handles the maths for powders, and our bacteriostatic water guide explains the diluent. None of this is a recommendation to use either peptide.

People searching for “selank and semax together” usually want to know whether the two can be combined. No clinical study has given them together, so there are no human data on the combination’s effects, interactions or safety. The fMRI study gave each peptide to separate groups, not both to the same person ^[11].

Two points from the labels are relevant. The Semax label lists disorders accompanied by anxiety, acute psychiatric states and a history of seizures among its contraindications ^[4]. And the Semax label advises against using other nasal products with a vessel-narrowing effect at the same time, because of the nasal route ^[4]. Neither label discusses combining Semax with Selank.

The Russian labels list few side effects. For Semax, mild irritation of the nasal lining with prolonged use ^[4]. For Selank, allergic reactions in people who are sensitive to it, and an unpleasant taste when drops run from the nose into the throat ^[9]. Both labels say the products should not be used in pregnancy or breastfeeding; Selank is not for anyone under 18, and Semax is not for children under 7 ^[4][9].

The clinical studies behind these labels were small and short, so uncommon or long-term harms may not have been detected. The US FDA’s compounding review lists Semax and Selank acetate among substances it previously placed in its category of bulk substances that may present significant safety risks, citing possible immune reactions from aggregation and peptide-related impurities; those nominations were later withdrawn ^[16]. Products bought online carry the additional risk that the contents do not match the label, which is a quality question, not a pharmacological one.

Both peptides are short-lived once in the blood. The Selank label says it appears in plasma 30 seconds after intranasal dosing and that plasma levels fall progressively over about five minutes, with no detectable metabolites after nasal use ^[9]. For Semax, the label describes rapid breakdown once in the bloodstream ^[4], and rat studies found it was quickly degraded, with the tripeptide Pro-Gly-Pro the main product ^[13]. Neither has a published human half-life in hours.

Both Russian labels state storage at 2 to 8 °C ^[4][9]. Research products sold as powders or pre-mixed sprays have no published stability data; general guidance is in our peptide storage guide.

In Russia, Semax 0.1% nasal drops are registered as a prescription nootropic and Selank 0.15% nasal drops as an anxiolytic sold without prescription, both made by Peptogen ^[4][9]. We found no marketing authorisation for either in the UK, US, Canada, Australia or New Zealand.

In the US, the FDA’s compounding page (as of April 2026) lists both among substances that were previously in its significant-safety-risk category and moved to a “nominated but withdrawn” section. Withdrawal is not authorisation: neither is on the list of bulk substances pharmacies may compound ^[16]. An FDA advisory committee considered Semax for that list on 24 July 2026; FDA’s meeting page posts no vote or outcome ^[19]. See US legal status.

In New Zealand, a May 2026 Medsafe consumer advisory lists Selank and Semax (spelt “sealank” and “seamax”) among peptide products advertised online, and states that it is illegal to import, sell or use these products ^[18]. See New Zealand legal status, and our UK legal status page for the rules on unlicensed medicines in Britain. Neither peptide is named on the WADA 2026 Prohibited List text we checked; athletes should ask their national anti-doping organisation.

We track prices for each peptide separately: Semax prices, Selank prices, and Semax suppliers in the UK. Blends and ready-made sprays are harder to compare because strengths vary and the label cannot be checked without a lab test. Our third-party testing guide explains what an independent test does and does not prove, and our list of third-party tested suppliers shows which vendors publish results.