Semax vs Selank: same laboratory, same delivery route, very different mechanisms.
Semax and Selank are the two most-researched cognitive peptides from the Russian neuropeptide tradition. They came from the same laboratory, use the same intranasal delivery format, and share the same Pro-Gly-Pro C-terminal stability extension. The similarities stop there. Mechanistically, in their primary clinical indications, and in the research questions they are best suited to address, Semax and Selank are quite different compounds — and conflating them is one of the most common misunderstandings in the nootropic research space.
- Semax is an ACTH(4–10) analog. Primary mechanism: BDNF upregulation, dopaminergic modulation. Primary Russian indication: cognitive enhancement, ischemic stroke neuroprotection.
- Selank is a tuftsin analog. Primary mechanism: GABA-A positive allosteric modulation, serotonergic modulation. Primary Russian indication: generalised anxiety disorder, neurasthenia.
- Both are registered by the Russian Ministry of Health and use intranasal delivery at 0.1–1% (Semax) or 0.15% (Selank) concentrations.
- Neither has a published Western (non-Russian) randomised controlled trial as of April 2026. Both have real Russian clinical literature — with the caveats described in each compound's dedicated spoke.
- The stacking rationale (using both together) is mechanistically plausible — complementary mechanisms — but has no direct clinical evidence.
- Selank is not a nootropic in the strict sense; it is an anxiolytic that may produce secondary cognitive benefits through anxiety reduction.
The head-to-head comparison table
| Dimension | Semax | Selank |
|---|---|---|
| Sequence | Met-Glu-His-Phe-Pro-Gly-Pro (7 aa) | Thr-Lys-Pro-Arg-Pro-Gly-Pro (7 aa) |
| Parent peptide | ACTH(4–10) fragment | Tuftsin (endogenous tetrapeptide Thr-Lys-Pro-Arg) |
| Primary mechanism | BDNF/TrkB upregulation; dopaminergic modulation | GABA-A positive allosteric modulation; serotonergic modulation |
| Secondary mechanism | Anti-inflammatory, mild serotonergic | Immunomodulatory (tuftsin component); mild dopaminergic |
| Primary Russian indication | Ischemic stroke; cognitive deficit | Generalised anxiety disorder; neurasthenia |
| Intranasal concentration | 0.1% (cognitive) / 1% (stroke) | 0.15% |
| Russian MoH registration | 1995 | 2009 |
| Key RCT reference | Myasoedov et al. 2001; Uchakina et al. 2008 (stroke) | Zozulya et al. 2008 (GAD/neurasthenia) |
| Sedation reported? | No | No |
| Western RCT? | No | No |
| FDA status | Not approved | Not approved |
Mechanism comparison in depth
Semax: dopaminergic and neurotrophic. Semax's strongest mechanistic claim is upregulation of brain-derived neurotrophic factor (BDNF) and its receptor TrkB, demonstrated in rat hippocampal tissue (Dolotov et al., Brain Research 2006, PMID 17010939). BDNF is a central mediator of synaptic plasticity, long-term potentiation, and neuronal survival. Upregulating it is consistent with the cognitive-enhancement and neuroprotective effects reported in the Russian literature. The secondary dopaminergic modulation provides a rationale for the attention and working-memory effects that Russian trials report.
Selank: GABAergic and anxiolytic. Selank's primary characterised mechanism is positive allosteric modulation of GABA-A receptors, the primary inhibitory receptor in the CNS (Seredenin & Voronin, 2009). Enhancing GABA-A activity reduces cortical arousal, sympathetic nervous system tone, and anxiety — which is the primary clinical effect observed. The secondary serotonergic modulation may contribute to mood stabilisation effects reported in Russian GAD trials.
Evidence comparison
Both compounds have Russian clinical evidence that is genuine but limited in Western-standard methodological detail. The key distinction is in primary indication:
Semax's primary clinical evidence comes from ischemic stroke rehabilitation — a disease-state model with hard outcomes (neurological deficit recovery, cytokine profile normalisation). Uchakina et al. (2008) and Myasoedov et al. (2001) are the key references. The cognitive-enhancement evidence for healthy or mildly cognitively-impaired populations is less formally studied.
Selank's primary clinical evidence comes from generalised anxiety disorder — Zozulya et al. (2008) is the key reference, with HAM-A score improvement vs placebo reported. The absence of dependence signal at 14-day follow-up is notable and differentiates it from benzodiazepines. No long-term safety data exist.
For the most comprehensive human evidence in the cognitive peptide category, neither Semax nor Selank matches Cerebrolysin, which has multiple Cochrane-reviewed Phase III RCTs and EMA registration. Researchers whose primary interest is evidence quality should read the Cerebrolysin spoke before the Semax or Selank spokes.
The stacking question
A common research question is whether Semax and Selank should be used together. Our dedicated Semax + Selank stack spoke covers this in detail. The short answer: the mechanisms are non-overlapping and theoretically complementary — BDNF upregulation plus anxiolysis plus dopaminergic modulation plus GABA-A modulation would not be expected to interfere, and together might address both the cognitive-enhancement and anxiety-management research goals simultaneously.
The longer answer: no clinical trial has studied the combination. The stacking rationale is based on mechanistic extrapolation, not direct evidence. Researchers considering both compounds simultaneously should read the mechanism sections for each compound separately and understand that the combined-use rationale is theoretical.
Choosing between them based on research goals
Choose Semax if the research question involves: direct cognitive enhancement (focus, working memory, processing speed), stroke or ischemic injury neuroprotection, BDNF biology, or dopaminergic modulation. Semax is the compound with the stronger direct nootropic evidence in the Russian literature.
Choose Selank if the research question involves: anxiety, cortical overarousal, stress-related cognitive impairment, GABA-A pharmacology, or the relationship between anxiety reduction and cognitive performance. Selank is the compound with the registered anxiolytic indication and the most direct Russian Phase II anxiolytic evidence.
Consider both together if the research question involves: the interaction between anxiety and cognition; combined neuroprotective and anxiolytic strategies; or investigation of the additive or synergistic effects of complementary peptide mechanisms. Be explicit that the combined-use rationale is mechanistically extrapolated, not clinically evidenced.
For focus-specific research applications where neither compound may be appropriate, our peptides for focus spoke covers the full cluster. For the nootropic market overview including both Russian peptides and the Western alternatives, our best nootropic peptides 2026 spoke provides the comparative landscape. For the Semax-vs-stimulants comparison specifically, see Semax vs modafinil.
Regulatory position: both compounds
Semax (Russian MoH, 1995) and Selank (Russian MoH, 2009) are both legally registered drugs in Russia. Neither is approved by the FDA, EMA, Health Canada, or any Western regulatory body. In the United States, both exist as unscheduled research chemicals — not controlled substances, but not approved for human use or legal for US compounding pharmacies to prepare and dispense. They are sold under research-use-only framing by research-chemical vendors. This shared regulatory status is a meaningful practical similarity between the two compounds, even though their pharmacology differs substantially.