Semax vs Selank

These two share an engineering trick rather than a biology. Both take a short, behaviourally active fragment of a larger molecule and bolt a proline-glycine-proline tail onto it so the result survives long enough to study. Everything else about them differs.

The same caveat applies to both: the clinical literature is substantial in volume, largely Russian-language, and predates modern trial reporting standards. Independent replication outside those groups is limited. That does not make the findings wrong — it does mean they carry less weight than a trial count alone suggests.

What each is reported to do

Semax research centres on rapid increases in BDNF messenger RNA in the hippocampus, alongside reported effects on dopaminergic and serotonergic signalling and on gene expression after ischaemia. Crucially it lacks the part of ACTH that stimulates cortisol, so it is not a corticosteroid-pathway compound.

Selank research describes anxiolytic activity through GABAergic signalling without the sedation associated with benzodiazepines — the claim that drew attention, and the one most in need of independent confirmation. Its tuftsin origin also gives it a strand of immune-parameter research that Semax does not have.

The combined vial

We also stock them pre-blended. The pairing is convenience and complementarity rather than a studied combination, and both compounds report effects on BDNF, so they are not fully independent levers.

The same engineering trick, twice

Both compounds solve the same problem. ACTH fragments and tuftsin are both behaviourally active and both degrade almost immediately, which makes them impossible to study in any practical way. Adding a proline-glycine-proline tail to the C-terminus protects against the peptidases that would otherwise clear them, and does it without altering the fragment that carries the activity.

Semax takes ACTH(4-7) — Met-Glu-His-Phe — and adds the tail. Crucially it leaves behind the part of ACTH responsible for stimulating cortisol release, so despite its origin it is not a corticosteroid-pathway compound. Selank takes tuftsin, a four-residue fragment of the immunoglobulin heavy chain with documented immune-modulating activity, and does the same thing.

That shared design makes them handle alike: both are seven residues, both are simple syntheses, both are stable enough to work with, and both are sold in amidated variants that differ in mass and are not interchangeable with the plain form.

What each is reported to do, in detail

The most-cited Semax finding is a rapid increase in BDNF messenger RNA in the rat hippocampus, along with its receptor TrkB. BDNF is central to synaptic plasticity, which is the bridge from a molecule to a cognitive effect — and the reason the finding is cited so often. Other reported activity includes modulation of dopaminergic and serotonergic signalling, and changes in expression of genes involved in neuroinflammation after ischaemic insult.

Selank research describes effects on GABA-A receptor expression and on serotonin metabolism, plus interference with enkephalin degradation. The claim that drew attention is anxiolytic activity through GABAergic signalling without sedation, tolerance or dependence — the properties that limit benzodiazepines. It is also the claim most in need of independent replication, because it is exactly what one would want to be true.

Both report BDNF effects, which is worth noting when they are described as complementary: they are not fully independent levers on different systems.

Reading a literature that sits outside the mainstream

Semax is registered in Russia for stroke and for cognitive indications, and Selank for anxiety. Clinical use in that market is long-standing and the publication count is substantial. Neither fact carries the weight it appears to.

The reason is methodological rather than national. Much of the work predates modern trial reporting standards — pre-registration, published protocols, intention-to-treat analysis, independent data monitoring — and is published in Russian-language journals that are not indexed or replicated internationally. A trial that cannot be checked is not evidence of the same grade as one that can, regardless of where it was run.

The honest summary: interesting compounds, a real body of clinical use, and an evidence base that would not currently support registration in Australia, the EU or the US.

Status in Australia

Neither is registered in Australia. An approval in Russia has no bearing on that, and a compound registered elsewhere is not "approved but not yet here" — it has simply never been assessed here.

For athletes, both fall within the WADA S0 catch-all for substances with no current approval for human therapeutic use in the relevant regulatory framework. OzPeptides supplies both for in-vitro and laboratory research only, to buyers aged 18 and over.

Which to choose for research

The split is straightforward: cognition, neuroprotection and BDNF work points to Semax; anxiety, stress models and GABAergic signalling points to Selank. Where a study touches both, the shared BDNF activity means they are not cleanly separable and a design using both should account for that.

We stock Semax in 5MG, 10MG and 30MG, Selank in 10MG and 30MG, and the two pre-blended at 10+10MG. The blend is convenience — one reconstitution, one batch — not a studied combination.

The intranasal question

Both were developed as intranasal formulations, and most of the Russian clinical work used nasal administration. The rationale is the olfactory route: it is one of the few paths that can reach the central nervous system without crossing the blood-brain barrier through circulation, and for peptides too large to cross it easily that is a real argument rather than a marketing one.

Research vials of both are supplied lyophilised, so the delivery route in any given study is a choice made in the laboratory rather than something the product dictates. It is worth noting because published dose figures generally refer to the intranasal route, and reading them as if they applied to any other is a straightforward way to misinterpret the literature.

Status and what to check

Neither peptide is registered in Australia. Both are registered medicines in Russia, which is where nearly all of the human data comes from, and that registration carries no weight here — a drug approved in one jurisdiction is not approved in another, and Australia has assessed neither.

Neither appears on the WADA Prohibited List, which is a factual point rather than an endorsement: unlisted is not the same as permitted, since the list is revised annually and anti-doping rules extend to substances with no current approval for human use.

Both are short, simple syntheses, so a genuine batch should test very clean. We make both in Blacktown at ≥99% HPLC purity with 0 ppm heavy metals, and the amidated variants of each are a separate product with a different mass — confirmed by mass spectrometry, not assumed from a label.

Frequently asked