✓ Medically reviewed by · Last reviewed: May 2026
Pharmacy Researcher · 8 years experience
Pharmacy researcher with 8 years reviewing clinical drug information, generic formulation equivalence, and international pharmaceutical standards. Focuses on patient-facing accuracy in medication education.
Key takeaways
- Both are Russian-developed heptapeptides with similar C-terminal stabilisation. Same engineering technique (Pro-Gly-Pro extension); completely different parent biology and receptor systems.
- Semax targets attention / cognition. ACTH 4-7 fragment; works through BDNF / NGF upregulation and dopaminergic effects.
- Selank targets anxiety / anxiolysis. Tuftsin fragment; works through GABA-system modulation and enkephalinase effects.
- Both have Russian Ministry of Health registration as finished pharmaceutical products. Neither has Western regulatory approval.
- This guide compares the two on mechanism, endpoints, dosing, and research applicability.
Selank vs Semax: Russian Anxiolytic vs Russian Nootropic Peptide Compared
Selank and Semax are the two best-known Russian-developed regulatory peptides. Both are heptapeptides built on the same engineering principle — a short biologically active core sequence with a C-terminal Pro-Gly-Pro extension that confers enzymatic stability. Both have Russian Ministry of Health registration as finished pharmaceutical products for specific clinical indications. The difference: completely different parent molecules and therefore completely different receptor systems and endpoints.
Quick verdict
- Attention / cognitive-performance research: Semax. The most-published cognitive peptide.
- Anxiety / anxiolytic-mechanism research: Selank. GABA-modulating tuftsin analogue without benzodiazepine-class side effects.
- Combined dual-arm research: Both. The two compounds are sometimes paired in research designs that need both attention and anxiolysis arms.
- Sleep research: Use DSIP instead — slow-wave-sleep-specific compound.
Mechanism: same engineering, different biology
Both molecules share an unusual engineering decision: take a short biologically active peptide that is rapidly degraded in plasma, add Pro-Gly-Pro to the C-terminus to block aminopeptidase cleavage, and end up with a heptapeptide stable enough for clinical-research dosing. The technique is one of the cleanest examples in peptide pharmacology of structural modification preserving target activity while engineering away the stability problem.
Semax is built on the ACTH 4-7 / 4-10 motif. Met-Glu-His-Phe is the active fragment from native corticotropin; Pro-Gly-Pro is the C-terminal stability extension. The molecule does NOT have ACTH receptor / steroidogenic activity (that’s in the N-terminal portion of native ACTH). Instead, the 4-7 fragment retains the CNS-active arm of ACTH activity: BDNF / NGF upregulation, dopaminergic system effects, and direct attention-circuit / stress-response neural-circuit effects. Russian published research documents efficacy in stroke recovery and attention disorders; Russian Ministry of Health registration covers these indications.
Selank is built on tuftsin. Tuftsin (Thr-Lys-Pro-Arg) is a tetrapeptide cleaved from the heavy chain of IgG with both immunomodulatory and CNS activity. Selank extends the tuftsin core with Pro-Gly-Pro. The molecule acts as a GABA-system modulator with anxiolytic activity but without the sedation, dependence, or cognitive-impairment profile typical of benzodiazepine-class drugs. Russian published research documents efficacy in generalised anxiety and stress-response modulation; Russian Ministry of Health registration covers generalised anxiety disorder.
Comparison table
| Property | Semax | Selank |
|---|---|---|
| Parent peptide | ACTH 4-7 fragment | Tuftsin (IgG-derived) |
| Sequence | Met-Glu-His-Phe-Pro-Gly-Pro | Thr-Lys-Pro-Arg-Pro-Gly-Pro |
| CAS | 80714-61-0 | 129954-34-3 |
| MW | 813.9 | 751.9 |
| Primary mechanism | BDNF / NGF + dopaminergic | GABA modulation + enkephalinase |
| Primary endpoint | Attention / cognition / stress-response | Anxiety / anxiolysis |
| Russian MoH registered indications | Stroke recovery, attention disorders | Generalised anxiety disorder |
| Sedation | None | None (unlike benzodiazepines) |
| Cognitive impairment | None (positive cognitive effects) | None (unlike benzodiazepines) |
| Dependence liability | None documented | None documented |
| Published routes | Intranasal (dominant), SC | Intranasal (dominant), SC |
| Typical research dose | 200-1000 mcg intranasal daily | 300-1200 mcg intranasal daily |
Which to pick (research-protocol logic)
- Attention / cognitive-performance research: Semax. The reference cognitive peptide. BDNF / NGF mechanism is well-documented.
- Anxiety / GABA-system mechanism research: Selank. The non-benzodiazepine anxiolytic.
- Stroke / neurorehabilitation research: Semax. Russian published research includes substantial neurorehab data.
- Stress-response neuroscience: Either or both, depending on whether attention or anxiolysis is the primary arm.
- Dual-arm protocols: Selank + Semax. Anxiolysis + cognition combined; the molecules don’t appear to interact pharmacokinetically.
- Sleep-architecture research: Neither — use DSIP for slow-wave-sleep-specific endpoints.
Safety and regulatory status
Both compounds have Russian Ministry of Health registration as finished pharmaceutical products for specific clinical indications. Neither has FDA / EMA / MHRA approval. The research-grade lyophilized peptides on the catalogue are sold for in-vitro laboratory research and analytical reference use only — they are the same molecules as the registered Russian finished products but not the registered finished products themselves. The published research safety profile across both compounds is favourable (no documented dependence liability, no sedation, no cognitive impairment, minimal cardiovascular signal), but absence of Western regulatory pharmacovigilance documentation means long-term safety in unstudied populations is uncertain. None of this is medical advice.
FAQ
Why are both heptapeptides with similar C-terminal extensions?
Same engineering decision. The native parent peptides (ACTH 4-7 for Semax, tuftsin for Selank) are rapidly degraded by aminopeptidases in plasma. Adding Pro-Gly-Pro to the C-terminus blocks the enzymatic cleavage site, extending half-life from minutes to a clinical-research-protocol-friendly window. The technique is one of the cleanest peptide-engineering examples of structural modification preserving target activity while engineering away the stability problem.
Can Semax produce anxiety effects (since ACTH is a stress hormone)?
No — Semax retains the BDNF / NGF / dopaminergic arm of ACTH 4-7 activity but does NOT have ACTH receptor / steroidogenic effects (those are in the N-terminal portion of native ACTH). Published Russian research documents Semax effects on stress-response modulation as stress-reducing rather than stress-amplifying. The molecule is anxiolysis-neutral or mildly anxiolytic in some research models, not anxiogenic.
Is Selank actually as effective as benzodiazepines for anxiety?
The published Russian clinical-research comparison shows Selank produces measurable anxiolytic effects without the sedation, dependence, or cognitive-impairment profile of benzodiazepines. The effect size for pure anxiolysis is generally modest compared with benzodiazepines but the clinical-positioning advantage (no dependence, no sedation) is the differentiator. For research-protocol design, Selank is the non-benzodiazepine GABA-modulator option.
How does the intranasal route compare with subcutaneous?
Both routes are published for both compounds. Intranasal is the route used in the Russian-registered finished products and dominates clinical-research applications. Subcutaneous is more common in Western mechanism-research applications. Bioavailability comparisons across routes are documented but vary between published studies; for research-protocol design, both routes are valid.
Can Selank and Semax be stacked?
Yes. Published research includes combination protocols using both compounds for dual attention + anxiolysis research designs. The two molecules act through non-overlapping mechanism arms (BDNF / dopaminergic for Semax; GABA / enkephalinase for Selank) and don’t appear to interact pharmacokinetically. Combined dosing is typically the standard individual dose for each compound, administered simultaneously.
What’s the research dosing protocol?
Intranasal: Semax 200-1000 mcg daily; Selank 300-1200 mcg daily. Subcutaneous research protocols use similar dose ranges. The published research is split between single-daily administration and twice-daily administration (morning + afternoon) depending on the endpoint.
How do these compare with Adamax?
Adamax is an emerging Semax follow-on with substantially narrower published research. Semax is the established-reference compound; Adamax is the frontier experimental option. For most research-protocol designs, Semax is the appropriate choice; Adamax is the experimental arm in protocols where Semax-comparator research is the design. See: Best nootropic peptides.
Storage protocol?
Lyophilized vials at -20 °C long-term or 2-8 °C as working stock; reconstituted with bacteriostatic water or appropriate intranasal-spray vehicle; reconstituted solution at 2-8 °C with use within ~30 days; protect from light; never freeze-thaw.
Bottom line
Semax and Selank are mechanistically distinct Russian-developed heptapeptides with the same C-terminal stability engineering. Semax is the attention / cognitive-performance reference compound (BDNF / NGF + dopaminergic mechanism). Selank is the non-benzodiazepine anxiolytic (GABA-modulator + enkephalinase). Both have Russian Ministry of Health registration but no Western regulatory approval. For research-protocol design, Semax handles the cognitive arm, Selank handles the anxiolytic arm, and the two combine without interaction when both arms are needed. See Best nootropic peptides for full CNS-cluster context.
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Written by
Sophie ChenPharmaceutical Content Researcher · 8 years experience
Sophie Chen is a pharmaceutical content researcher with 8 years covering generic medication access and clinical pharmacology. She specialises in international regulatory frameworks, bioequivalence standards, and patient-facing education on therapeutic drug classes. She is not a clinician.