Semax

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

It was developed in Russia and is used there as a nootropic and neuroprotective drug. It is often discussed alongside Selank, a Russian heptapeptide that ends in the same Pro-Gly-Pro sequence, and both are sold by research peptide vendors as “nootropics”.

Most mechanistic work comes from Russian laboratories. In rats, tritium-labelled Semax bound specifically to membranes from the basal forebrain, and intranasal Semax at 50 and 250 µg/kg rapidly increased levels of brain-derived neurotrophic factor (BDNF), a protein involved in nerve-cell survival and learning ^[1]. A single 50 µg/kg dose increased hippocampal BDNF protein about 1.4-fold and its receptor activation about 1.6-fold, and treated rats performed better on an avoidance-learning task ^[2].

In rats with experimental stroke (permanent blockage of a brain artery), Semax increased activity of genes for neurotrophins and their receptors in the damaged cortex ^[3], and a genome-wide study found its largest effects were on immune-response and blood-vessel-related genes ^[4]. These findings are from animals and have not been shown to translate into clinical benefit in rigorous human trials.

The animal work suggests effects on BDNF signalling, learning in rodents, and gene activity after experimental stroke ^[1][2][3][4]. It comes largely from one research network, and we found few independent replications outside Russia.

Human studies have been published in Russian, mostly in stroke. A 1997 study gave Semax to 30 patients in the acute phase of ischaemic stroke and compared them with 80 patients on conventional treatment; the authors reported some effect on the rate of neurological recovery, especially motor function ^[5]. This was not a randomised, placebo-controlled design. A 2018 study of 110 patients in rehabilitation after ischaemic stroke found that those given Semax had higher blood BDNF levels and better improvement on the Barthel index of daily living, although allocation and blinding are not described in the English abstract ^[6].

No large, randomised, placebo-controlled trials have been published, and we found no trials registered or published outside Russia. Claims about memory, focus or mood in healthy people are not supported by controlled human evidence.

In the 1997 acute stroke study, daily doses of 12 mg (moderate strokes) and 18 mg (severe strokes) for 5 to 10 days were reported as most effective ^[5]. The 2018 rehabilitation study used two 10-day courses of 6,000 µg (6 mg) per day, 20 days apart ^[6]. The registered Russian product is a 0.1% nasal solution ^[7]. Rat studies used intranasal doses of 50 to 250 µg/kg ^[1][2]. These are doses reported in studies, not recommendations, and animal doses cannot be converted to human doses.

The Russian product information lists mild irritation of the nasal lining with prolonged use as a possible side effect, and states that it should not be used in pregnancy or breastfeeding ^[7]. The published clinical studies were small and not designed to detect uncommon adverse effects. The US FDA’s compounding page (as of April 2026) lists Semax among substances previously placed in its category of bulk substances that may present significant safety risks, citing a potential immunogenicity risk from aggregation and peptide-related impurities; the nomination was later withdrawn ^[8].

Products sold outside Russia are unregulated. A Belgian medicines laboratory identified Semax and Selank in seized preparations and noted that such peptides are freely sold online as powders and nasal sprays ^[9].

In Russia, Semax nasal drops 0.1% are registered (registration ЛП-№(009449)-(РГ-RU), March 2025) with Peptogen as manufacturer, classed as a nootropic and dispensed on prescription ^[7]. We found no marketing authorisation in the UK, US, Canada, Australia or New Zealand. See our legal status overview and the UK and US pages.

Research-grade Semax is usually sold as a freeze-dried powder or pre-made nasal spray. General guidance is in our peptide storage guide.

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