What is the difference between Semax and Selank?

They act on different systems. Semax is derived from the ACTH(4-10) fragment and is studied mainly for stimulating BDNF (a key neurotrophin) and supporting cognition and neuroprotection. Selank is derived from the immune peptide tuftsin and is studied mainly for anxiolytic effects via GABAergic modulation, without the sedation seen with benzodiazepines. In short: Semax leans cognitive/neuroprotective, Selank leans anxiolytic.

Can Semax and Selank be used together?

In research they are frequently studied in parallel because their mechanisms are complementary — BDNF stimulation (Semax) alongside GABAergic anxiolysis (Selank). There is no clinical protocol for the combination outside their separate Russian approvals; the rationale for studying them together is mechanistic, not a proven combined therapy.

Are Semax and Selank approved drugs?

In Russia, Semax is approved (since 2001) for cerebral circulatory disorders and Selank (since 2008) as an intranasal anxiolytic. In the US, UK and EU neither is an approved medicine — they are distributed as research peptides for laboratory use only, and are not for human or veterinary use.

How are Semax and Selank reconstituted?

Both are lyophilized heptapeptides reconstituted with bacteriostatic water added slowly down the vial wall, then swirled gently — never shaken. A 5 mg vial in 1 mL gives 5 mg/mL. Store the reconstituted solution refrigerated at 2–8 °C, protected from light, and use within about two weeks.

Semax vs Selank: Two Russian Nootropic Peptides Compared

Semax and Selank are both synthetic heptapeptides developed in Russia and studied as nootropics, but they target different systems. Semax is an ACTH(4-10) analog studied for BDNF stimulation and cognitive/neuroprotective effects; Selank is a tuftsin-derived peptide studied for anxiolytic GABAergic modulation without sedation. They are distinct molecules, often researched in parallel. Both are research reagents only — not for human or veterinary use.

The short answer

Semax and Selank are often mentioned in the same breath because they share a back-story — both are synthetic heptapeptides developed at the same Russian institute (IHF, Moscow) and both are studied as nootropics. But they are different molecules built from different parent peptides, and they pull on different levers. The simplest framing: Semax is the cognitive/neuroprotective one; Selank is the calming/anxiolytic one.

Side-by-side comparison

Property	Semax	Selank
Parent peptide	ACTH(4-10) fragment	Tuftsin (an immune tetrapeptide)
Sequence length	Heptapeptide (7 amino acids)	Heptapeptide (7 amino acids)
Primary mechanism	Stimulates BDNF / TrkB; neuroprotective signalling	GABAergic modulation; enkephalinase inhibition
Studied mainly for	Cognition, attention, neuroprotection	Anxiety reduction without sedation
Russian approval	2001 — cerebral circulatory disorders	2008 — intranasal anxiolytic
Sedation / dependence	Not a sedative; not a dependence concern	Anxiolytic without sedation or dependence (vs benzodiazepines)
Reconstitution	Bacteriostatic water; 5 mg in 1 mL = 5 mg/mL	Bacteriostatic water; 5 mg in 1 mL = 5 mg/mL

Semax: BDNF and cognition

Semax is based on the ACTH(4-10) fragment, but engineered to keep the neurotrophic activity while dropping the adrenocorticotropic (cortisol-stimulating) effect — so it does not push the HPA stress axis. Its central research mechanism is stimulating expression of BDNF (brain-derived neurotrophic factor) and its receptor TrkB, with downstream neuroprotective signalling via the Ras-MAPK and PI3K-Akt pathways. That is why the literature clusters around attention, memory and neuroprotection. Full mechanism and citations are on the Semax product page.

Selank: GABAergic anxiolysis

Selank is built from tuftsin, an immunomodulatory tetrapeptide, extended to make it stable enough to study. Its defining research activity is GABAergic modulation — influencing GABA-A receptor subunit expression to produce an anxiolytic effect without the sedation or dependence associated with benzodiazepines. It also influences BDNF and modulates enkephalin degradation, giving it a secondary cognitive angle, but its primary research framing is anxiety. Detail is on the Selank product page.

Why they are studied together

Because one leans cognitive and the other leans calming, the two are frequently investigated in parallel as complementary tools: Semax for BDNF-driven cognitive support, Selank for GABAergic anxiolysis. There is overlap (both touch BDNF), but the dominant mechanisms are distinct, which is exactly what makes the pairing interesting to researchers.

Regional approval is not global approval. Both are approved medicines in Russia only. Outside Russia they are research reagents with no human efficacy or safety approval, and nothing here is medical advice or a dosing recommendation.

For purity, storage and reconstitution standards that apply to both peptides, see the complete research peptides guide and the reconstitution guide.

For research use only. Not for human or animal use. Not a drug outside their Russian approvals. The mechanisms summarised above reflect published research and are not medical advice or claims of efficacy for the research-grade peptides.