Semax + Selank Blend
How this combination works
Semax and Selank are proposed as a complementary pair because their principal functional profiles are broadly orthogonal: Semax is characterised in the community as the stimulating/nootropic component (activating NGF, BDNF, and cognitive circuits via ACTH-related pathways), while Selank is the anxiolytic component (blunting anxiety and enhancing calmness via enkephalinase inhibition and GABA-A modulation). Community users report that Selank moderates stimulatory side effects sometimes experienced with Semax alone, producing a combined profile of enhanced focus plus reduced anxiety. Both compounds inhibit enkephalin-degrading enzymes in human serum — Semax at IC50 ~10 µM and Selank at IC50 ~15–20 µM — which represents a mechanistically shared pathway that may produce additive or overlapping enkephalinergic effects. One human neuroimaging study directly compared Semax and Selank in the same 52-subject experiment and found both general and compound-specific effects on amygdala–temporal cortex functional connectivity; this study compared them in parallel arms rather than testing co-administration, and does not constitute evidence of combination benefit. One rat Parkinson's model study administered both compounds in the same experiment — Selank reduced anxiety while Semax had no effect on the behavioural measures tested. Neither study tests co-administration as a stack. The synergy rationale is therefore: community consensus (primary basis) + mechanistic inference from shared enkephalinase inhibition pathway. No direct co-administration evidence in humans or animals is available.
Combined mechanism
Semax (Met-Glu-His-Phe-Pro-Gly-Pro) acts as an ACTH(4-10) analogue devoid of hormonal activity, upregulating NGF and BDNF gene expression in the hippocampus and frontal cortex, suppressing proinflammatory gene expression (Il1a, Il1b, Il6, Ccl3, Cxcl2) under ischemic conditions, and modulating GABA-activated ionic currents in cerebellar Purkinje cells and hippocampal pyramidal neurons. Its metabolic fragments (HFPGP, PGP) form a 'synacton' system with distinct receptor binding. Selank (Thr-Lys-Pro-Arg-Pro-Gly-Pro) is a tuftsin analogue that inhibits enkephalin-degrading enzymes in plasma (IC50 ~15 µM; PMID 11550013), prolongs endogenous leu-enkephalin half-life as a proposed primary anxiolytic mechanism, and acts as a positive allosteric modulator of GABA-A receptors at a site potentially overlapping with benzodiazepine binding. Both compounds inhibit enkephalinases — Semax at IC50 ~10 µM, Selank at IC50 ~15 µM — which is a shared mechanistic pathway. Both also modulate BDNF levels in the hippocampus and prefrontal cortex. The combination is hypothesised to produce complementary cognitive enhancement (Semax-driven) and anxiolysis (Selank-driven) through engagement of these separate but partially overlapping systems. The human fMRI study demonstrated that the two peptides have distinct and overlapping effects on resting-state amygdala–temporal cortex functional connectivity, indicating both compounds engage shared brain circuits but via different mechanisms; critically, this study used parallel treatment arms, not co-administration. No pharmacokinetic data on drug-drug interactions between the two compounds exist in the reviewed literature.
What each component does
Administered intranasally in the majority of community and clinical protocols; subcutaneous injection is a less common alternative discussed in community sources
View full peptide page →SelankAdministered intranasally in community protocols; available in lyophilized form for injection; intranasal is the dominant community route
View full peptide page →Community dosing protocols
All protocols below are community-reported. No clinical dosing guidelines exist for this combination.
| Goal / context | Semax | Selank | Frequency | Duration | Notes |
|---|---|---|---|---|---|
| Cognitive enhancement (focus, memory, mental clarity) balanced with anxiolysis and mood stabilization commonly reported | 600 mcg intranasal morning, taken first | 500 mcg intranasal morning, taken shortly after Semax (same session) | once daily in the morning | 4–8 weeks on, 2–4 weeks off | Semax at 600 mcg and Selank at 500 mcg (or 250–500 mcg) intranasal is the canonical Semax + Selank combination described across r/Peptides, r/nootropics, and biohacker reference sites. Both are administered intranasally in the morning. Community users report Selank moderates the stimulatory edge sometimes experienced with Semax alone. Semax dose drawn from approved file synthesis (common_dose_range: 300 mcg); 600 mcg reflects the most cited standard stack dose. Selank dose drawn from approved file synthesis (common_dose_range: 250 mcg twice daily); morning single-dose 500 mcg reflects the most cited co-use amount. |
| Entry-level nootropic stack — mild cognitive boost with anxiolytic modulation commonly reported | 300 mcg intranasal morning | 250 mcg intranasal morning, same session as Semax | once daily in the morning | 2–4 weeks on, 1–2 weeks off | Conservative starting protocol for first-time users of the combination. Doses match the entry-level doses from each compound's approved file synthesis field. Community frequently recommends starting at the lower end before titrating up to the standard 600/500 mcg protocol. |
Most reported: 300–600 mcg intranasal (morning) Semax + 250–500 mcg intranasal (morning, same session) Selank · once daily in the morning · 4–8 weeks on, 2–4 weeks off
Evidence base for this combination
- Panikratova et al. Doklady Biological Sciences. 2020.HUMAN PARALLEL COMPARISON STUDY PMID 32342318
Resting-state fMRI study in 52 healthy participants comparing Semax, Selank, and placebo in separate groups (parallel arms). Found both general effects shared by both peptides and compound-specific effects on functional connectivity between the right amygdala and right temporal cortex. This study does NOT test co-administration; it compares the two peptides independently. It provides the strongest available human evidence that both compounds modulate overlapping brain circuits, supporting the mechanistic basis for the community-reported combination rationale, but does not directly demonstrate combination benefit.
- Slominsky et al. Doklady Biological Sciences. 2017.ANIMAL PARALLEL COMPARISON STUDY PMID 28702721
Rat 6-OHDA Parkinson's model study in which both Semax and Selank were administered in the same experiment. Selank decreased anxiety in the elevated cross-shaped maze; Semax did not affect motor activity or passive defensive behaviour in the same model. Compounds were administered to separate animal groups — not co-administered. This is parallel testing, not a combination study.
Safety considerations for this combination
- No human co-administration safety data exist for Semax + Selank. The two human studies that mention both compounds (PMID: 32342318, 28702721) used parallel treatment arms, not co-administration, and did not report combination-specific adverse effects. PMID: 32342318, 28702721
- Semax Selank both inhibit enkephalinases (PMID: 11443939, 11550013). Co-administration could produce greater than expected prolongation of endogenous enkephalin activity. The clinical implications of this additive enkephalinase inhibition are unstudied. Mechanistic inference from PMID: 11443939 (Semax) and PMID: 11550013 (Selank)
- Selank modulates GABA-A receptor activity as a positive allosteric modulator; combined use with Semax (which independently modulates GABA currents in cerebellar Purkinje cells; PMID: 29577196) could produce additive or unpredictable GABAergic effects. Mechanistic inference: Selank GABA-A modulation (PMID: 30255741); Semax GABA current modulation (PMID: 29577196)
- Selank is characterised as 'poorly studied' with inadequate evaluation of abuse potential, dependence, and withdrawal prior to public access (PMID: 34396551). These concerns inherit to any combination protocol. PMID: 34396551
- Both compounds are non-approved peptides with limited long-term safety data and no systematic clinical validation. Non-approved peptides as a class lack long-term safety data (PMID: 42021992). PMID: 42021992
Contraindications
- Selank is a positive allosteric modulator of GABA-A receptors and has been shown in vitro to block the modulatory activity of diazepam and olanzapine at these receptors (PMID: 30255741). Co-use of the Semax + Selank blend with benzodiazepines, antipsychotics, or other GABAergic drugs may produce unpredictable pharmacodynamic interactions. This signal is inherited from Selank and applies to the combination. Inherited from Selank (PMID: 30255741)
- Selank demonstrated anticoagulant effects in animal thromboelastography studies — the highest anticoagulation potency among tested glyproline peptides (PMID: 29181670). Individuals taking anticoagulants, antiplatelet agents, or with bleeding disorders should be aware of this potential signal. No human data on this interaction exist. Inherited from Selank (PMID: 29181670)
- Neither Semax nor Selank has been approved by any regulatory authority. Both are poorly characterised for human safety. Selank has not completed clinical trials and has been identified as potentially dangerous by Belgian regulatory analysts (PMID: 31667971). The combination has not been evaluated in any co-administration study. Inherited from Selank (PMID: 34396551, 31667971); Semax regulatory status not established in reviewed literature
- Semax Ac-modification (N-terminal acetylation) abolished its cytoprotective copper-chelating effects in vitro (PMID: 27586814). Some commercially available preparations may not use the correct N-terminal form. Purchasers should verify the form (Semax vs. Ac-Semax) before use. Inherited from Semax (PMID: 27586814)