Semax: benefits, side effects, nasal spray and what the research shows

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”.

Two strengths are registered in Russia, both as nasal drops made by Peptogen: a 0.1% solution, in which one drop contains 50 µg, and a 1% solution, in which one drop contains 500 µg ^[7][10]. Vendors outside Russia also sell “N-acetyl Semax amidate” (NA-Semax), a modified version with an acetyl group on the first amino acid and an amide group on the last. That form is not the registered drug (see N-acetyl Semax vs Semax below).

What is Semax used for? Officially, only what the Russian labels list. The 0.1% product is indicated for memory and thinking problems caused by vascular brain disease, recovery after stroke, transient ischaemic attacks, recovery after head injury, neurosurgery or anaesthesia, optic nerve atrophy and optic neuritis, raising adaptation to extreme conditions and preventing mental fatigue, and, in children from 7 years, minimal brain dysfunction including ADHD ^[7]. The 1% product is indicated only for the acute period of moderate or severe ischaemic stroke, as part of combined treatment ^[10].

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.

Other parts of the Semax mechanism of action proposed by Russian groups involve brain chemical messengers. In rodents, 0.15 mg/kg by injection raised a marker of serotonin turnover in the striatum to as much as 180% of its starting level over 1 to 4 hours; Semax alone did not change dopamine, but given before amphetamine it greatly increased amphetamine’s effect on dopamine release and movement ^[12]. In human serum, Semax inhibited enkephalin-degrading enzymes at about 10 µM ^[13]. The Russian label describes it as a synthetic analogue of corticotropin with nootropic properties and no hormonal activity, with an “original” mechanism that it does not further define ^[7].

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.

The subsections below cover each use people search for, with the human evidence, if any, stated plainly.

The developers’ own 1997 review stated that intranasal Semax at 0.015 to 0.050 mg/kg improved memory and attention in animals and people for 20 to 24 hours, including in healthy men working under extreme conditions ^[11]. The underlying studies are Russian and we could not assess their design from English sources. The two indexed studies in healthy volunteers measured brain activity, not performance. In one, 24 volunteers received intranasal 1% Semax or placebo, and the Semax group showed a larger frontal part of the brain’s default mode network on resting-state MRI 5 and 20 minutes later ^[15]. In the other, 52 healthy participants received Semax, Selank or placebo, and both peptides changed amygdala connectivity ^[16].

These results show that Semax does something measurable in the brain. They do not show that it improves focus, learning or memory in healthy people, and no placebo-controlled trial has tested that outside Russia.

Most Semax ADHD claims trace back to the Russian 0.1% label, which includes minimal brain dysfunction, including ADHD, in children aged 7 and over, with a 30-day course ^[7]. We found no controlled trial of Semax in ADHD indexed in PubMed. A 2007 paper in the journal Medical Hypotheses proposed Semax as a potential ADHD treatment, based on its effects on dopamine and BDNF in animals ^[21]. A hypothesis paper is not evidence of benefit.

Stroke is where most of the clinical work sits (see Human studies below). In addition, a Russian study of 187 patients with chronic cerebrovascular insufficiency reported clinical improvement, slower disease progression and fewer strokes and transient ischaemic attacks with Semax, and good tolerability, including in older patients ^[17]. The English abstract does not describe randomisation or a control group in enough detail to judge the result.

Russian ophthalmologists have added Semax to standard treatment for optic nerve disease. In one study, patients given Semax as nasal drops or by endonasal electrophoresis alongside standard therapy recovered visual acuity, visual field and colour vision faster than controls ^[19]. Another reported advantages for glaucomatous optic neuropathy when Semax was added to neuroprotective treatment ^[20]. Both are small, older, Russian-language studies.

In rats under chronic unpredictable stress, daily injections of Semax at a low dose reversed loss of interest in sugar water, reduced adrenal enlargement and restored hippocampal BDNF, effects the authors called antidepressant-like; Melanotan II, tested alongside it, did the same ^[23]. There are no human depression trials.

Two unusual uses have small human studies. In patients with peptic ulcers that had not healed on standard drugs, 89.5% of those given 1% Semax nasal drops for 10 days had healed by day 14, compared with 30.8% of controls ^[22]. In 27 patients with motor neuron disease, 12 mg a day of 1% Semax in two 10-day courses did not change nerve or clinical measures but improved a quality-of-life score, mainly through mood and motivation ^[18]. Neither has been repeated.

People also search for Semax for bodybuilding. We found no study of Semax on muscle, strength or body composition.

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.

So does Semax work? For stroke recovery the Russian studies report benefit, but with designs that would not meet current international standards. For cognitive enhancement in healthy people there are imaging changes and developer claims, not controlled outcome data. Nearly all of the literature is in Russian or in small journals, and most of it comes from groups that developed the drug.

The developers reported effects lasting 20 to 24 hours after a single intranasal dose ^[11], and brain-imaging changes in volunteers were seen within 5 to 20 minutes ^[15]. Clinical courses were measured in days: 10-day courses after stroke ^[6], a maximal quality-of-life effect on day 10 in motor neuron disease ^[18] and ulcer healing assessed on day 14 ^[22]. No controlled study has measured how quickly a healthy person notices an effect, so reports of effects within minutes come from users, not trials.

Semax was developed as a nasal drug. The Russian labels state that 60 to 70% of the active substance is absorbed through the nasal lining, that it spreads quickly through the body and crosses the blood-brain barrier, and that once in blood it is quickly broken down and excreted in urine ^[7][10]. For optic nerve disease, the label also describes delivery by endonasal electrophoresis, using a small electric current ^[7]. The labels advise against using nasal decongestant drops that constrict blood vessels at the same time ^[7].

We found no published human studies of Semax injections. Animal studies used injections into the abdomen ^[12][23], but those doses do not translate to people. The label notes that Semax is rapidly destroyed and does not reach the gut ^[7], and nothing suggests a Semax supplement or capsule taken by mouth would be absorbed intact.

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 labels are the only official dosing source. For the 0.1% drops, the label gives single doses of 200 to 2,000 µg and daily doses of 800 to 8,000 µg, as 2 to 3 drops per nostril four times a day for 10 to 14 days, for memory problems caused by vascular brain disease; 400 to 900 µg a day for 3 to 5 days to prevent mental fatigue; 600 to 900 µg a day for 7 to 10 days in optic nerve disease; and 200 to 400 µg a day for 30 days in children from 7 years with minimal brain dysfunction ^[7]. For the 1% drops in acute stroke, the label gives 6,000 to 12,000 µg a day in moderate stroke and 12,000 to 20,000 µg a day in severe stroke, for 10 days ^[10].

Other published human regimens include 12 mg a day in motor neuron disease ^[18] and 2 to 4 drops of 1% Semax three times a day for 10 days in peptic ulcer ^[22]. Vendor Semax peptide dosing charts, subcutaneous protocols and “how much Semax to inject” guides are not drawn from these sources. For vial arithmetic, such as Semax 10mg reconstitution, the concentration is the peptide amount divided by the liquid volume; our peptide calculator and bacteriostatic water guide explain the numbers without implying any dose.

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]. See how to spot a fake peptide supplier.

The Russian labels list contraindications that matter for people self-sourcing Semax: acute psychiatric states, disorders accompanied by anxiety, a history of seizures, hypersensitivity, and age under 7 years (under 18 for the 1% product and for eye and neurosurgical uses) ^[7][10]. Semax nasal spray side effects in the label are limited to mild nasal irritation with long use ^[7], and the 2005 cerebrovascular study described a small proportion of side effects ^[17].

On Semax hair loss, we found no mention of hair loss in the Russian labels or in the study abstracts we read. That is an absence of reports, not proof of safety. We also found no study of a Semax alcohol interaction in people.

We found no published human Semax half-life figure. The labels describe rapid breakdown once Semax reaches the blood ^[7][10]. A Russian laboratory study found that nerve cells break Semax down mainly into the five-amino-acid fragment HFPGP and the three-amino-acid PGP ^[14], and PGP itself had activity on neurotrophin genes in rats ^[3]. This is one reason the developers argue that effects can outlast the peptide.

N-acetyl Semax amidate is sold as a stronger or longer-lasting Semax. We found no human study of it. Laboratory work on the acetylated form is limited; one 2016 study found that acetylation changed how Semax binds copper and that, unlike plain Semax, the acetylated form did not protect nerve-like cells from copper toxicity ^[24]. Claims that N-acetyl Semax is several times more potent are not supported by published human data.

Semax vs Selank is the comparison people search most. Both are Russian heptapeptides ending in Pro-Gly-Pro. Semax is built on the 4-7 fragment of ACTH and is registered as a prescription nootropic ^[7]. Selank is built on the immune peptide tuftsin and is registered as an over-the-counter anxiolytic in 0.15% drops ^[25]. Semax’s label lists disorders accompanied by anxiety as a contraindication ^[7], while Selank’s label lists anxiety states as its main indication ^[25]. Our Semax vs selank comparison sets the two side by side.

In human serum both inhibit enkephalin-degrading enzymes, Semax at about 10 µM and Selank at about 20 µM ^[13]. In the only direct study in people, 52 healthy volunteers, each peptide changed amygdala connectivity compared with placebo, with some shared and some distinct effects ^[16]. In rats with a Parkinson’s-like lesion, Selank reduced anxiety while neither peptide changed movement ^[27]. No trial has compared their effects on anxiety, focus or memory in people.

Semax and Selank nasal spray blends and combined dosage charts are common in vendor catalogues. We found no study that gave the two together, in people or animals; the studies that included both tested them separately ^[16][27]. The combination’s effects and safety are unknown, and blend dosing charts are not based on research. We also found no study combining Semax, Selank and oxytocin.

Adamax is a vendor name for a modified Semax-like peptide. We found no peer-reviewed studies of Adamax indexed in PubMed, so it cannot be compared with Semax on evidence. Dihexa is an unrelated experimental compound; like Semax, it appears on the FDA’s 2026 list of compounding nominations that were withdrawn, which is not an authorisation ^[8].

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.

The 1% drops are separately registered (ЛП-№(010596)-(РГ-RU), June 2025), also on prescription ^[10]. Is Semax FDA approved? No. Semax is not an approved drug in the US. The FDA moved it in 2026 to a group of compounding nominations that were withdrawn, which does not authorise compounding ^[8]. The FDA’s Pharmacy Compounding Advisory Committee considered Semax on 24 July 2026; as of FDA’s August 2026 page, no outcome or FDA decision had been posted ^[26]. For Canada, see the Canadian legal status page.

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

You can compare prices, learn how to read a COA, and see our list of third-party tested suppliers.

Country pages list Semax in the UK and Semax in the US. A listing is not a statement that a product is legal to buy or appropriate to use. Our methodology explains how suppliers are assessed.