Semax vs Selank: which Russian nasal peptide actually fits you?

Semax is an ACTH(4-10) analog that pushes BDNF and trkB for focus, cognition, and recovery; Selank is a tuftsin analog that blocks enkephalinase for calm without sedation. Both are intranasal, both lean on small Russian trials and rodent data, and neither is FDA-approved. Pick Semax for drive, Selank for anxiety.

If you spend any time in nootropics forums, these two peptides come up constantly, usually together, and usually with a lot of confident claims that the underlying research does not support. So let me lay it out straight. Both are short peptides. Both are sprayed up the nose. Both came out of the same cluster of Moscow research institutes. And both have a "focus vs calm" reputation that is roughly accurate but messier than the marketing implies.

Here is the head-to-head before we get into the why.

what Semax actually is

Semax is a synthetic heptapeptide, Met-Glu-His-Phe-Pro-Gly-Pro. It's built from the ACTH(4-7) fragment with a Pro-Gly-Pro tail bolted on the end. That tail matters: it slows enzymatic breakdown, which is why a fragile peptide survives long enough to do anything. Despite the ACTH lineage, Semax is non-corticotropic. It does not jack up cortisol. The adrenocorticotropic part of the parent molecule was, in effect, engineered out, leaving the neurotropic behavior behind.

The core mechanism, at least in rodents, is the BDNF/trkB system. BDNF is brain-derived neurotrophic factor, the growth factor most tied to learning, plasticity, and neuron survival; trkB is its receptor. According to PubMed, a single intranasal dose of Semax at 50 mcg/kg in rats produced roughly a 1.4-fold rise in hippocampal BDNF protein, about a 1.6-fold increase in trkB phosphorylation, and 3-fold and 2-fold jumps in BDNF and trkB mRNA, with the animals showing better conditioned avoidance learning PMID: 16996037 (DOI). A related study found rapid, region-specific bumps in BDNF and NGF gene expression within an hour of the same dose PMID: 17353092 (DOI).

There's also binding evidence that this isn't some vague nonspecific effect. Semax binds specific, reversible, calcium-dependent sites in rat basal forebrain with a KD around 2.4 nM, and intranasal dosing raised BDNF protein within three hours PMID: 16635254 (DOI). A KD in the low nanomolar range is the kind of affinity you'd expect from a real receptor interaction, not background noise.

For humans, the meaningful data is a stroke trial. In 110 ischemic-stroke patients, the standard Russian regimen of 6000 mcg/day (two 10-day courses with a 20-day gap) raised plasma BDNF and sped up motor recovery and Barthel index improvement PMID: 29798983 (DOI). Semax is a registered drug in Russia for stroke and cognitive indications. It is not approved by the FDA or any Western regulator.

One nuance worth flagging: Semax is not purely a stimulant-style focus drug. Chronic dosing in rats (0.05 mg/kg daily for 10-14 days) produced anxiolytic and antidepressant-like effects, attributed to serotonergic activation plus higher hippocampal BDNF PMID: 17850024. A 2024 study in a chronic unpredictable stress model showed Semax (60 nmol/kg/day) blunted anhedonia, adrenal hypertrophy, and the stress-driven drop in BDNF PMID: 39442746 (DOI). So the "Semax = focus only" story is incomplete.

You can dig into the full mechanism breakdown on the Semax compound page.

what Selank actually is

Selank is also a heptapeptide, Thr-Lys-Pro-Arg-Pro-Gly-Pro. It's a synthetic analog of tuftsin, an endogenous immunopeptide, and goes by the lab name TP-7. Same Pro-Gly-Pro stabilizing tail as Semax, different head.

Its leading mechanism is enkephalinase inhibition. Enkephalins are your endogenous opioid peptides, and they get chewed up quickly by enkephalin-degrading enzymes. Selank slows that breakdown, so your own enkephalins stick around longer. In human plasma it inhibits enkephalin hydrolysis with an IC50 around 15 uM, more potently than the reference inhibitors bacitracin and puromycin, and patients with generalized anxiety showed shortened enkephalin half-life that Selank helped normalize PMID: 11550013 (DOI). The mouse data backs this up: 100 mcg/kg produced an anxiolytic effect in the open-field test and lengthened leu-enkephalin half-life in anxiety-prone BALB/c mice PMID: 12432865 (DOI).

The standout human study is a 62-patient comparative RCT against medazepam, a benzodiazepine, in generalized anxiety disorder and neurasthenia. Selank matched the benzo's anxiolytic effect, added anti-asthenic and mild psychostimulant effects, and normalized leu-enkephalin half-life PMID: 18454096. Matching a benzo without the sedation, tolerance, and dependence is the whole pitch for Selank. The trial is small, single-center, and Russian, so hold it loosely, but it exists and it's a real RCT.

Selank's anxiolytic profile is durable, not just acute. The tuftsin analog TP-7 (which is Selank) at 0.3 mg/kg cut anxiety-phobic behavior in rats from day 2 and held over four weeks, with no effect on body weight PMID: 16963804. And like Semax, it touches cognition: Selank at 0.3 mg/kg/day for a week prevented ethanol-withdrawal memory deficits while normalizing BDNF in the hippocampus and frontal cortex PMID: 31625062 (DOI). It also has documented immunomodulatory and antiviral activity, altering chemokine and cytokine gene expression in spleen PMID: 21786679.

More detail lives on the Selank compound page.

the mechanisms side by side

The clean story is: Semax works through neurotrophins (BDNF/trkB), Selank works through the endogenous opioid system (enkephalinase inhibition). That heuristic holds up. But notice the overlap. Semax shows anxiolytic and antidepressant effects in rodents. Selank normalizes BDNF and helps cognition in a withdrawal model. The two are not as cleanly separated as "stimulant vs calmer" suggests, because both ultimately nudge plasticity and mood-related circuitry, just from different entry points.

Here's where it gets murky, and I'd rather say it plainly: the bulk of mechanistic data is rodent, and the human data is two small Russian trials plus a registry approval. There are no large, blinded, placebo-controlled Western trials. There is no independent replication. Be skeptical of anyone who tells you either peptide is "proven" for memory, anxiety, or anything else outside the Russian regulatory context.

dosing, route, and onset

Both peptides get destroyed in the gut, so the standard route is intranasal. That's why you see them sold as atomized nasal sprays rather than capsules. If you're new to intranasal delivery, the intranasal dosing tool covers technique, and if you're working with lyophilized powder, the reconstitution calculator handles the math.

On dose, I have to draw a hard line between what's in the literature and what people actually do:

In practice, intranasal Semax is commonly dosed around 300-600 mcg/day, often split, with subjective focus or alertness reported within roughly 15-60 minutes. Selank runs a similar intranasal range, around 250-900 mcg/day, with a calming onset people describe within 30-60 minutes. Again: these onset times and doses are not from controlled Western trials. They're what the community reports.

who each one suits

If your bottleneck is drive, mental stamina, recall, or you're chasing neuroprotection and recovery, Semax is the more logical pick. The BDNF/trkB mechanism and the stroke data both point that direction.

If your bottleneck is anxiety, a racing mind, or stress that wrecks your focus, Selank is the more logical pick. It calms without the sedation, dependence, or next-day fog of a benzodiazepine, which is exactly what the GAD trial measured.

safety and the honest caveats

In the mostly Russian literature, both peptides show clean short-term tolerability, no benzodiazepine-style dependence, no sedation, no documented withdrawal. That's reassuring as far as it goes. It does not go very far. Long-term human safety data outside Russia is essentially nonexistent.

Both are research-use-only. They are not approved for human consumption in the US, EU, UK, or most other Western jurisdictions. If you have a psychiatric condition or take psychiatric medication, talk to a clinician first, especially with Selank, since its enkephalin mechanism touches the opioid system and the interaction profile with serotonergic or opioid drugs is unstudied. Avoid both if pregnant or nursing. Interactions broadly are unknown.

where to get research-grade material

Quality matters more here than with most supplements, because peptide purity and accurate labeling are not guaranteed in a gray market. For research-use-only Semax and Selank, BHG Labs sells both as atomized nasal products that are lot-numbered and linked to third-party certificates of analysis (COA), which is the bar you want before anything goes near your body.

• Semax (atomized nasal, ~$54.99): BHG Labs Semax
• Selank (atomized nasal, ~$54.99): BHG Labs Selank

Use code REDDIT for 10% off.

further reading

• Semax compound profile
• Selank compound profile
• Noopept, the racetam-adjacent nootropic
• Tesofensine for appetite and focus
• Intranasal dosing tool
• Vendor scorecard

Research citations retrieved from PubMed. Where available, DOI links are included inline next to each citation.

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