Semax vs Selank: Evidence, Doses and Differences

The Quick Answer

Semax and Selank are different molecules built for different jobs on paper. Semax is a synthetic heptapeptide derived from a fragment of the hormone ACTH, and its Russian label classes it as a nootropic. Selank is a synthetic analogue of tuftsin, a naturally occurring peptide, and its Russian label describes an anti-anxiety action. In Russia the two carry almost non-overlapping indications: Semax for cognitive and stroke-related uses, Selank for anxiety states.

The evidence behind those labels is uneven and, for humans, thin. The strongest human data in the research set behind this page are two resting-state fMRI studies in healthy volunteers, one on both compounds and one on Semax alone, and neither reports a microgram dose. Two 2026 review articles, one naming both peptides and the other naming Semax, describe the clinical trial base as limited.

In the United States, neither is an FDA-approved drug. A 2020 FDA warning letter named both among bulk substances that made compounded products misbranded, and the FDA compounding page currently lists both under nominations that were made and then withdrawn. No Vietnamese pharmacy listing was found for either, and the official Vietnamese register could not be read in this research, so their Vietnamese status is simply unknown.

This page does not pick a winner. This research found no head to head trial that establishes one as more effective than the other for any condition, and neither is an approved drug in the United States. What follows is what the sources actually say.

What Each One Actually Is

Semax is a synthetic heptapeptide. Its Russian label describes it as an analogue of the ACTH 4-10 fragment, stripped of hormonal activity, with all amino acids in the L form, and names the active substance methionyl-glutamyl-histidyl-phenylalanyl-prolyl-glycyl-proline. The label puts it under ATC code N06BX, in the group it calls nootropics. One point of confusion worth clearing up: some newer papers describe the same molecule as the ACTH(4-7) fragment joined to a Pro-Gly-Pro tail rather than ACTH 4-10. Both descriptions refer to the same seven-residue peptide. The difference is only whether the trailing Pro-Gly-Pro is counted inside the ACTH fragment or named separately, so these are not two different compounds.

Selank is also a synthetic heptapeptide, but from a different starting point. It is an analogue of the endogenous, naturally occurring peptide tuftsin, with the sequence threonine-lysine-proline-arginine-proline-glycine-proline (Thr-Lys-Pro-Arg-Pro-Gly-Pro). Its Russian label describes an anti-anxiety action with an antidepressant and anti-asthenic component. The FDA, for its part, lists the two under different chemical names again: Selank acetate (TP-7) and Semax (heptapeptide).

What they share is real but limited. Both are short synthetic peptides, both are sold in Russia as intranasal drops, and both are described as analogues of naturally occurring peptides. Their labels describe different pharmacokinetics, though: the Selank label has its plasma concentration falling over about 5 to 5.5 minutes, while the Semax label describes a sequential breakdown whose fragments carry most of the effect for a stated 20 to 24 hours. A 2026 review groups them together as neuroactive peptides said to influence brain-derived neurotrophic factor and related pathways, although it presents that as a mechanism summary and not a measured result. For the standalone detail on each, see the Semax profile and the Selank profile.

What Each Label Is For

The clearest practical difference is what each is actually aimed at. In Russia, where both are marketed products, the two labels point in almost opposite directions, and in one respect they directly conflict. These are the label indications as printed, not endorsements of the uses.

What the Human Studies Show

Set expectations here. The research set behind this page contains two human studies, both using resting-state functional MRI in healthy volunteers, and both measure brain activity rather than a clinical outcome such as anxiety scores or cognitive test results.

The first looked at both compounds. Fifty-two healthy participants had resting-state fMRI before and 5 and 20 minutes after an injection of Semax, Selank or placebo, and the authors reported effects on functional connectivity between the right amygdala and a right-hemisphere temporal region (dose not stated in the abstract, PMID 32342318). The abstract calls the route an injection and does not give a dose in micrograms.

The second looked at Semax alone. Twenty-four healthy volunteers, 14 on Semax and 10 on placebo, had resting-state fMRI before and 5 and 20 minutes after intranasal 1% Semax, and a larger volume of one default-mode-network subcomponent was seen in the Semax group (dose not stated in the abstract, PMID 30225715). The strength is given, 1%, but the absolute dose in micrograms is not.

For Selank specifically, the only clinical-efficacy sentence in the set is second-hand. An in vitro paper states in its background that clinical studies have shown Selank had an anxiolytic effect comparable to classical benzodiazepine drugs, but that sentence names no trial, no number of participants and no dose (PMID 28293190). Treat it as an assertion to note, not as trial evidence to rely on.

Two 2026 review articles in this research set are blunt about the gap. One says that although preclinical studies are promising, there is a current lack of clinical trials (PMID 41490200). The other says the non-approved peptides in its scope show promising preclinical and limited clinical evidence but lack long-term safety data, and lists optimal dosing regimens among the significant knowledge gaps (PMID 42021992).

The Animal and Lab Studies

Most of the measured evidence for both peptides is in animals and cell systems, and this is where the actual dose figures in the studies live. These are animal doses, quoted as the papers state them. None of them is a human dose or a recommendation.

For Selank, several rat studies used intraperitoneal injection. In a social-stress model, rats received Selank at 100 mcg/kg per day for 20 days, with cytokine changes reported (animal study, rats, intraperitoneal, PMID 32621722). One caution the research file flags on that paper: its results paragraph says Semax while its title, methods and conclusion say Selank, a contradiction that is in the published abstract itself, so the cytokine result cannot be pinned cleanly to either compound. In a chronic foot-shock stress model, Wistar rats received Selank at 100, 300 and 1000 mcg/kg 15 minutes before each stress session, with the largest stress-limiting effect on liver morphology reported at 300 mcg/kg (animal study, Wistar rats, intraperitoneal, PMID 31243679). A restraint-stress study used the same three doses in male Wistar rats and reported liver oxidative and enzyme changes (animal study, male Wistar rats, intraperitoneal, PMID 28853100).

In a morphine-withdrawal model, outbred rats received a single Selank dose of 0.3 mg/kg, described as an anxiolytic dose, which reduced a total withdrawal index by 39.6 percent and was slightly less active than diazepam at 2 mg/kg (animal study, outbred rats, intraperitoneal, PMID 36322304). In cell systems, Selank behaved as a positive allosteric modulator of GABA binding in isolated brain-cell membranes (in vitro, dose not stated in the abstract, PMID 30255741), while in human IMR-32 neuroblastoma cells it produced no change in the mRNA levels of the GABAergic genes studied (in vitro, dose not stated in the abstract, PMID 28293190).

For Semax, a spinal-cord-injury study in female mice reported improved functional recovery and reduced pyroptosis (animal study, female C57BL/6 mice, route not stated in the abstract, PMID 40692165). A stroke-model study in rats using transient middle cerebral artery occlusion reported that Semax and a related peptide reduced ischemia-driven changes across 1171 genes at 24 hours (animal study, rats, route not stated in the abstract, PMID 39767736). A further study of synthetic corticotropins that include the Semax sequence found that preliminary peptide administration did not influence one stress effect in a restraint-stress test (animal study, rats, dose not stated in the abstract, PMID 36828803).

None of these animal or cell results has been shown to carry over to a human outcome, and the reviews above say as much. For the broader class of research peptides, see the HGH peptides guide.

Side by Side Comparison

The table makes the asymmetry visible. The Semax label is specific about micrograms: it prints the content of one drop and single and daily dose ranges in both micrograms and micrograms per kilogram. The Selank label, as fetched, prints the concentration and the number of drops but never a microgram figure per drop or per day, so a microgram dose for Selank cannot be sourced from it.

Neither microgram figure comes from a human trial. Both come from the labels. That is the honest ceiling on what a dose comparison between these two can be.

What the Labels Print for Dosing

Because there is no trial dose to report, the only dose figures that exist for either compound are the ones printed on the Russian labels. They are reproduced here as published, for reference, and none of them is a recommendation or a schedule for anyone to follow. Dosing is a decision for a licensed clinician working from the actual product information, not from a web page.

Semax 0.1% nasal drops. The label states that one drop of the standard solution contains 50 mcg of active substance (Russian label figure, not a recommendation). For adults it prints no more than 2 to 3 drops into each nasal passage per administration, a single dose of 200 to 2000 mcg (given as 3 to 30 mcg/kg) and a daily dose of 500 to 5000 mcg (given as 7 to 70 mcg/kg), with the course running daily for 3 to 5 days and extended to 14 days if needed (Russian label, not a recommendation). Separate label schedules cover optic-nerve conditions (daily dose 600 to 900 mcg, 7 to 10 days), endonasal electrophoresis (daily dose 400 to 600 mcg, 7 to 10 days) and paediatric minimal brain dysfunction from age 5 (daily dose 200 to 400 mcg, 30 days) (Russian label, not a recommendation).

Semax 1% nasal drops. This is a separate, higher-strength product that the label restricts to the acute period of ischemic stroke, where one drop equals 0.05 ml and contains 500 mcg (Russian label figure, not a recommendation). The stroke schedules are large: for moderate stroke the label prints a daily dose of 6000 mcg (12 drops) to 12000 mcg (24 drops), and for severe stroke 12000 mcg (24 drops) to 20000 mcg (40 drops), given daily for 10 days (Russian label, not a recommendation). These are the label acute-stroke figures, not general-use doses, and this research found no fetched clinical trial supporting them. The schedule exists on the label without a trial cited on the page.

Selank 0.15% nasal drops. Here the label is built differently. It gives the concentration, 1.5 mg of active substance per 1 ml, and the regimen, 2 drops into each nasal passage 3 times a day for a 14-day course, repeatable after 1 to 3 weeks on medical advice, in adults aged 18 and over (Russian label, not a recommendation). What it does not print, in the version fetched for this page, is the microgram content of a single drop or any single or daily dose in micrograms. So unlike Semax, there is no sourced microgram dose to quote for Selank.

One limit worth stating plainly: none of these figures is a human trial dose. Every microgram number in this section comes from a product label, and the two labels were written for different regulatory systems and different clinical uses.

Side Effects on the Labels

The entire adverse-effects section of the Semax label is a single sentence: with prolonged use, slight irritation of the nasal mucous membrane is possible. The same label also states that no overdose has been detected to date even with a significant increase in the single dose, and makes a strong toxicology claim, that the drug is practically non-toxic on single and prolonged use and shows no allergenic, embryotoxic, teratogenic or mutagenic properties and no local irritant action. Those last two points sit in tension on the same page: one sentence describes local nasal irritation, another says there is no local irritant action, and both are printed in the same label.

The Selank label lists two adverse effects, both at a frequency it calls not known: allergic reactions, including delayed ones, and unpleasant taste when the product runs from the nose onto the throat. It adds a separate warning that the product contains methylparahydroxybenzoate, which may itself cause allergic reactions. The label states that no overdose cases have been registered and that Selank does not cause drug dependence or habituation.

The contraindications differ in a way worth repeating. Semax 0.1% is contraindicated under age 5. Selank is contraindicated under age 18, with the label giving the reason plainly, that clinical studies were not conducted in that group. Both are contraindicated in pregnancy and lactation. And, as noted above, the Semax label additionally contraindicates disorders accompanied by anxiety, acute psychoses and a history of convulsions.

The strongest sourced statement on human safety for either is, in fact, from the FDA, and it is a statement about missing information rather than about harm. On Selank the agency writes that compounded selank acetate may pose a risk for immunogenicity for certain routes of administration and that it lacks important information regarding any safety issues raised in humans. On Semax it writes the same immunogenicity concern and that it lacks sufficient information to know whether the drug would cause harm if administered to humans. The 2026 gerontology review in this research set likewise flags the absence of long-term safety data for the non-approved peptides in its scope (PMID 42021992).

Regulatory Status: FDA and Russia

In Russia both are marketed products, though the fetched paperwork differs between them. The Selank label names a marketing-authorisation holder, the Innovative Research and Production Centre Peptogen, and states that it is dispensed from pharmacies without a prescription. The Semax monograph as fetched shows an official instruction approved by the manufacturer in 2008, with an approval date of 09.08.2008, which establishes an approved instruction, although the fetched page does not print a registration-certificate number or a dispensing status for Semax. This research did not query the Russian State Register directly, so the Semax certificate number and prescription status remain unconfirmed here.

In the United States neither is an approved drug. A 2020 FDA warning letter to Tailor Made Compounding LLC named Selank and Semax in a list of bulk substances and stated that products compounded from them are not the subject of a USP or NF monograph, are not a component of an FDA-approved human drug, and do not appear on the 503A bulks list, which makes those products misbranded. On the FDA compounding-risk page, current as of April 2026, both appear, but specifically under the heading bulk substances nominated but withdrawn, described as substances previously in category 2 that were withdrawn by the nominators.

Those two FDA records carry a nuance worth keeping straight. In April 2020 the warning letter stated that Semax and Selank had not been nominated for inclusion on the 503A bulks list. The 2026 compounding page lists both under nominations that were made and then withdrawn. Both statements are quoted as fetched, so this page reports both rather than flattening them into one. Either way, the practical result is the same: neither is on the live list of substances the FDA has cleared for this kind of compounding, and neither is an approved drug.

Vietnam Availability Reality

If you are searching from Vietnam, here is what this research could and could not establish. On Long Chau, a Vietnamese pharmacy chain, a search for Semax and a separate search for Selank each returned no matching product. That is a genuine result, not a loading error: the chain ships its search data inside the page, so it was read directly, and in both cases the spelling suggestions from the chain itself pointed elsewhere entirely, to products such as maxxhair and melanov.

Two other chains could not be checked. The Pharmacity search page loaded but returned no server-side results and did not even echo the query, and the An Khang site reset the connection before returning anything. Both of those are tooling blocks, not evidence that the products are absent.

The official picture is genuinely unknown. The Vietnamese Drug Bank did not resolve from the research host, and the Drug Administration of Vietnam public register could not be queried because its search endpoint did not accept the requests tried. So this page does not claim that Semax or Selank is registered in Vietnam, and it does not claim that either is unregistered. The only defensible statement is that no Vietnamese pharmacy listing was found and the official register could not be read.

Because no Vietnamese listing was found, there is no published Vietnamese price to quote for either compound. Anyone checking current status should confirm it with the Drug Administration of Vietnam or a licensed pharmacy directly, not with a guide, including this one. See also the Peptides Vietnam FAQ for related questions.

The Bottom Line

Semax and Selank are easy to lump together, two Russian nasal peptides frequently compared, but the sources pull them apart. Semax descends from an ACTH fragment and is labelled as a nootropic aimed at cognitive and stroke-related uses. Selank descends from tuftsin and is labelled for anxiety and stress. In Russia their indications barely overlap, and the Semax label actually contraindicates the anxiety territory the Selank label is written for.

On evidence, both are thin where it counts. The human data in this research set are two brain-imaging studies in healthy volunteers, neither reporting a dose. The measured dose-response work is in rats and cells, and two 2026 reviews say the clinical trial base is limited. Every human dose figure here comes from a product label, not a trial.

On status, neither is FDA approved, both sit on the FDA withdrawn-nomination compounding list, and their Vietnamese standing could not be established in this research. That is the honest shape of it.

This page does not tell you which to use, what to take, or where to buy. Neither is an approved drug in the United States, and this research found no head to head trial to rank them. If you are considering either, that is a conversation for a licensed clinician, and any product decision in Vietnam should be checked against the Drug Administration of Vietnam rather than a web page.

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