Semax vs Selank 2026

Semax and Selank get grouped together for good reason. Both are seven-amino-acid peptides, both came out of the same Moscow institute, both end in the same three-amino-acid tail, and both are studied mostly as nasal drops. That is where the overlap stops. Semax is built from a fragment of a stress hormone and is studied for attention, memory and recovery after stroke. Selank is built from an immune peptide and is studied for anxiety and stress. One sharpens; the other settles.

This guide puts the two side by side the way a researcher needs them: the sequences, what each does at the receptor and gene level, the regimens written into the Russian labels, how to mix a 10mg vial to match those label strengths, and what the measured Semax and Selank batches from Simms Research contain.

Semax vs Selank at a glance

The short version fits in one grid. Each row below is expanded later in the guide.

Where Semax and Selank come from

Both peptides trace back to the Institute of Molecular Genetics of the Russian Academy of Sciences and to the chemist Nikolai Myasoedov, whose name appears on most of the foundational papers for each.

Semax started with a problem from Dutch research in the 1970s. David de Wied’s group showed that tiny pieces of the hormone ACTH, as short as ACTH 4-10 and even ACTH 4-7, improved learning in rats without acting as hormones. The catch was lifespan: those fragments were broken down in about a minute. A Soviet program run with Moscow State University set out to build a version that lasted. Most peptide-cutting enzymes struggle with proline-rich sequences, so the team capped ACTH 4-7 with Pro-Gly-Pro. That tail made the effect both stronger and about 50 times longer than the natural fragment. The result, Met-Glu-His-Phe-Pro-Gly-Pro, was first described in 1991, entered Russian clinical practice in the 1990s, and was added to Russia’s list of vital and essential drugs on 7 December 2011. The name is a contraction of the Russian for “seven amino acids”.

Selank applied the same trick to a different starting point. Tuftsin (Thr-Lys-Pro-Arg) is a four-amino-acid peptide released from an antibody fragment in the spleen, where it activates immune cells. Adding Pro-Gly-Pro gave Thr-Lys-Pro-Arg-Pro-Gly-Pro, which kept a share of tuftsin’s immune activity and added a calming effect on behavior. It was developed with the Zakusov Institute of Pharmacology, registered in Russia in 2009 as Selank 0.15%, and moved from prescription to over-the-counter sale in 2017.

The shared Pro-Gly-Pro tail is the family resemblance. It is also why both peptides break down into smaller pieces that carry part of the activity, a point that comes up again under mechanism.

How Semax works

The best-documented action of Semax is on brain-derived neurotrophic factor (BDNF), the protein that supports the growth and survival of neurons and the strengthening of synapses during learning. In a 2006 Brain Research study, one intranasal dose of 50mcg per kg in rats raised BDNF protein in the hippocampus 1.4-fold and activation of its receptor, TrkB, 1.6-fold. Messenger RNA for BDNF rose threefold and for TrkB twofold, and the treated rats learned an avoidance task faster. The hippocampus is the memory hub of the brain, which is why this result anchors most of what is written about Semax and cognition.

Several other actions sit alongside it. Semax inhibits the serum enzymes that break down enkephalins and other regulatory peptides, with a half-maximal concentration of 10 micromolar in a 2001 enzyme study, so the brain’s own signaling peptides last longer. It interacts with melanocortin receptors, where it has been shown to block the action of alpha-MSH at the MC4 and MC5 subtypes. Animal work shows rapid activation of dopamine and serotonin systems, and antidepressant-like and anti-stress effects under chronic stress.

Human data comes mostly from neurology. In a 1997 acute-stroke study, Semax added to standard care in 30 patients sped up recovery of motor and general neurological function compared with 80 matched controls, with 12mg a day working best for moderate strokes and 18mg a day for severe ones. In a 2018 study of 110 stroke patients, two 10-day courses of 6,000mcg a day, 20 days apart, raised blood BDNF for the whole five-month observation period and improved scores on the Barthel index of daily function. In healthy volunteers, a 2018 brain-imaging study found measurable changes in the brain’s default mode network 5 and 20 minutes after one intranasal dose of the 1% solution, against placebo.

Speed and duration explain the nasal route. The manufacturer reports Semax in brain tissue within 5 minutes of a nasal dose, peak levels at 30 minutes, and an active concentration that holds for 20 to 24 hours. In the bloodstream it is broken down quickly into Met-Glu-His-Phe and Pro-Gly-Pro, and both fragments carry activity of their own. About 60 to 70% of a nasal dose is absorbed.

How Selank works

Selank’s anti-anxiety action runs through the GABA system, the brain’s main braking signal and the same system benzodiazepines act on. The difference is how. Receptor-binding work published in 2018 found that Selank changes GABA binding as a positive allosteric modulator: it adjusts how strongly the receptor responds to the GABA already present rather than switching the receptor on itself. In a 2016 gene-expression study, Selank and GABA were each given to rats and 84 genes involved in nerve signaling were measured in the frontal cortex. Selank changed the expression of 45 of them within an hour, and its pattern tracked the pattern produced by GABA, which supports the same conclusion from a different angle.

It shares the enkephalin effect with Semax. In the same 2001 enzyme study, Selank inhibited the enkephalin-degrading enzymes of human serum with a half-maximal concentration of 20 micromolar. In patients with generalized anxiety, low stability of leu-enkephalin in the blood tracked how long and how severely they had been ill, and that stability rose during Selank treatment.

The tuftsin half of its ancestry shows up in immune measurements. In a 2008 immunology study, Selank at 10^-7 molar completely suppressed IL-6 gene expression in blood cells from patients with depression but not in cells from healthy controls, and 14 days of treatment shifted the Th1/Th2 cytokine balance in patients with generalized anxiety and neurasthenia.

The clinical anchor is a 2008 clinical trial in 62 patients with generalized anxiety disorder or neurasthenia. Thirty received Selank and 32 received medazepam, a benzodiazepine. The anti-anxiety effect was similar between the two, and Selank also reduced fatigue and had a mild stimulating effect, the opposite of the drowsiness benzodiazepines are known for. Intranasal bioavailability is reported at 92.8%, the peptide appears in plasma within about 30 seconds, and its breakdown products, Thr-Lys-Pro, Arg-Pro and Gly-Pro, keep much of the activity.

Which one fits the research question

The cleanest way to choose is to start from the endpoint. Semax is the peptide for measuring attention, learning speed, memory consolidation, mental work capacity and recovery after ischemic injury. Selank is the peptide for measuring anxiety, stress response, mood stability and the fatigue that comes with chronic stress. The Russian labels draw the same line from the other side: the Semax label lists disorders accompanied by anxiety among the conditions it is not used for, while the Selank label is written around anxiety, panic, neurasthenia, unstable mood, sleep disturbance and indecision.

Two other names come up in the same searches. Adamax and N-acetyl Semax amidate are newer, chemically modified versions of Semax sold in the research market, with far less published work behind them. Neither has the stroke trials or the decades of label use that Semax has, which is why the original sequence remains the reference compound in this family.

Using Semax and Selank together

Pairing the two is the logical next step, and it is common enough that combined nasal sprays are sold with both peptides premixed in one bottle. The case for the pair is mechanistic: one raises the neurotrophic signal behind learning, the other lowers the anxiety that interferes with it, and they share only the enkephalin effect. No human trial has tested the pair together. The published work studies each one alone, and the only direct side-by-side data is the 2001 enzyme study, where both slowed the same enzymes in serum.

Nothing in either label argues against combining them. The Selank instructions state that it does not change the effect of drugs that depress or stimulate the nervous system and can be combined with other psychoactive and neuroactive therapy. In a 2017 rat study, Selank given together with diazepam produced a stronger anti-anxiety effect under chronic stress than either alone, which shows Selank layering onto another GABA-active compound rather than clashing with it. The Semax instructions predict no pharmacokinetic interactions, because the peptide is absorbed and broken down so quickly, and advise against nasal decongestants, which narrow the vessels the drops are absorbed through.

Timing follows the labels. Semax regimens for mental work put the doses in the first half of the day. Selank’s regimen is three doses spread across the day. A pair protocol that respects both puts Semax in the morning and early afternoon and Selank across the day, including the evening if sleep or evening stress is part of the question.

Premixed sprays fix the ratio. Every spray delivers both peptides in the same proportion, so raising one means raising the other. Mixing each 10mg vial on its own lets each be set to its own label strength and dosed on its own schedule, which also keeps the two results separable when something changes.

Semax and Selank dosage in the published research

The most specific dosing information for either peptide is in the official Russian instructions, because both are licensed medicines there. Both are given as nasal drops, and both labels work in drops of a standard solution. One drop is 0.05mL. At the 0.1% Semax strength that drop holds 50mcg; at the 0.15% Selank strength it holds 75mcg.

Two practical rules sit under those numbers. The Semax label caps a single sitting at 2 to 3 drops per nostril; when a dose needs more, it is split into several sittings 10 to 15 minutes apart, because the nasal lining only absorbs so much at once. And the drops go onto a clear nasal passage with the head tipped slightly back or to the side, followed by a few seconds of pressing the nostril closed. Heavy mucus lowers absorption, which is why the Selank instructions advise clearing the nose first.

The ranges are wide on purpose. The low end of the Semax table is the healthy-adult regimen, and the high end is acute neurology. Outside stroke work, the reference points are 400 to 900mcg of Semax a day and the single Selank regimen of 900mcg a day.

Mixing a 10mg vial of Semax or Selank

Simms Research supplies both peptides as 10mg of white freeze-dried powder. The water volume decides the strength, so the useful question is which volume reproduces a label strength. The grid below shows the common choices, with the amount in one 0.05mL drop and in 0.1mL.

The label strengths take more water than a small vial holds. The usual approach is to dissolve the powder in 1 or 2mL first, then move a measured share of that concentrate into a separate sterile vial or dropper bottle and bring it up to volume. For example, 1mL of a 2mL mix holds 5mg; adding 2.33mL of water to it gives 3.33mL at 1.5mg/mL, the Selank label strength, and adding 4mL gives 5mL at 1mg/mL, the Semax 0.1% strength. The Simms Research peptide calculator handles any other combination.

A single vial goes a set distance at label doses. At the healthy-adult Semax regimen of 400 to 900mcg a day, 10mg covers about 11 to 25 days. At the Selank regimen of 900mcg a day, 10mg covers about 11 days, so a full 14-day Selank course on the label regimen needs 12.6mg, a little more than one vial.

The water goes in slowly down the inside wall of the vial rather than straight onto the powder, then a gentle swirl or roll finishes the job; shaking is unnecessary and can foam the solution. Both peptides dissolve readily and should end up perfectly clear and colorless. Research Water from Simms Research is bacteriostatic water, sterile water with 0.9% benzyl alcohol, in a 10mL vial: enough for the full Semax 0.1% dilution or several rounds of the stronger mixes. Once mixed, both peptides go in the refrigerator at 2 to 8°C and are used within 28 days; Do Peptides Need to Be Refrigerated? covers the storage details.

Side effects and tolerance

Both peptides have unusually short side-effect lists for compounds that act on the brain. The Semax label names one side effect: mild irritation of the nasal lining with long use. It reports no overdose effects even when the single dose was raised substantially, and the manufacturer states there is no tolerance or withdrawal, recommending a repeat course after three to six months to maintain the effect. Because Semax is stimulating, its label keeps it to the first half of the day for healthy adults.

The Selank label lists an unpleasant taste when drops run from the nose into the throat, mostly in people with a sensitive sense of taste and smell, and the allergic reactions possible with any compound. No overdose has been recorded. In the 2008 trial its anti-anxiety effect matched medazepam while adding a mild stimulating effect instead of drowsiness, and its Russian instructions permit driving and machine work during use. The label also states it is safe alongside alcohol-containing products.

Where the labels draw lines, they are plain. Semax is not used in acute psychiatric states, in disorders accompanied by anxiety, or with a history of seizures. Neither is used in pregnancy or breastfeeding, where neither has been studied, and Selank’s label is written for adults.

What is in a Simms Research vial

Both Semax and Selank from Simms Research are 10mg vials of white freeze-dried powder at $45 each, with 10% off three or more vials and 15% off six or more. Every batch goes to an independent lab, and the current batches of both were tested on three separate vials for purity, identity, net peptide content, endotoxins, heavy metals and microbial sterility.

The net content line matters for the mixing math. Every figure in the mixing grid assumes exactly 10mg. The current Semax vial holds 11.17mg, so 10mL of water gives about 1.12mg/mL rather than 1mg/mL, and the current Selank vial at 10.54mg gives about 1.05mg/mL in the same volume. Researchers who want the exact label strength can scale the water to the measured content: 11.17mL for Semax at 0.1%, or 7.03mL for Selank at 0.15%.

Each certificate is published batch by batch on the Semax lab results page and the Selank lab results page, alongside the rest of the lab results library. The guide on how to read a peptide certificate of analysis explains what each line on those certificates measures. Sealed vials keep best in the refrigerator, dry and away from light, with freezing at minus 20°C for long-term storage; as a dry powder, both tolerate room temperature for weeks, which is why they ship without ice.

Frequently asked questions

Can Selank and Semax be used together?

Yes. Neither label argues against it, the Selank instructions state it can be combined with other psychoactive and neuroactive therapy, and the two share only one mechanism, the slowing of enkephalin-degrading enzymes. No human trial has tested the pair together, so protocols that use both rely on each peptide’s own label regimen, usually with Semax in the morning and Selank spread across the day.

Is Semax good for ADHD?

The Russian Semax label includes children aged 7 and over with minimal brain dysfunction, a category that covers attention deficit hyperactivity disorder, at 200 to 400mcg a day split between morning and afternoon for 30 days. Outside Russia the evidence is mechanistic: a 2007 paper in Medical Hypotheses proposed Semax for ADHD because it raises BDNF and, in animal work, strengthens the dopamine release produced by stimulants. No Western clinical trial has tested it.

What peptide is better than Semax?

It depends on the endpoint. For attention, memory and stroke recovery, Semax is the best-documented peptide of its kind, and its modified versions, Adamax and N-acetyl Semax amidate, have much less research behind them. For anxiety and stress, Selank fits better, since the Semax label excludes anxiety disorders and Selank’s is built around them.

Are Semax and Selank safe?

Both have short side-effect lists. The Semax label names mild nasal irritation with long use; the Selank label names an unpleasant taste if drops reach the throat and the usual possibility of allergy. Neither label reports overdose effects, and Selank matched a benzodiazepine on anxiety in a clinical trial without causing drowsiness.

When is the best time to take Semax and Selank?

The Semax regimen for mental work places all doses in the first half of the day, because Semax is stimulating. Selank’s label regimen is three doses spread across the day, and because it calms without sedating, it fits the evening as well as the daytime.

How long does it take Semax and Selank to work?

Both act within minutes of a nasal dose. The manufacturer reports Semax in brain tissue within 5 minutes and at peak levels by 30 minutes, and Selank in the bloodstream within about 30 seconds. Both are reported to keep an active effect for 20 to 24 hours. Course effects build over the 10 to 14 days the labels set.

How long can you cycle Semax and Selank?

The Semax label sets 10 to 14 days for most uses and 3 to 5 days for short adaptation use, with the manufacturer recommending a repeat course after three to six months. The Selank label sets 14 days, repeatable after a break of one to three weeks.

Can you take Selank every day?

Daily use is how the label is written: 2 drops in each nostril three times a day for 14 days, or 900mcg a day at the 0.15% strength, followed by a break before any repeat course.

Is Semax or Selank better for anxiety?

Selank. It acts on the GABA system, matched medazepam on anxiety in a 62-patient trial, and its label lists anxiety, panic and stress disorders. The Semax label lists disorders accompanied by anxiety among the conditions it is not used for.

Does Selank help with sleep?

Sleep disturbance is among the conditions in Selank’s Russian indications, and it calms without acting as a sedative. Semax is the poorer choice near bedtime, since its regimen keeps doses before midday.

What should not be mixed with Semax?

The Semax instructions advise against nasal decongestants given through the nose, because they narrow the vessels the drops are absorbed through. They predict no other drug interactions, since Semax is absorbed and broken down so quickly.

Are Semax and Selank legal?

In the US both are sold as research peptides for laboratory use; neither is an approved medicine there.