Head-to-head comparison
| Property | Selank | Semax |
|---|---|---|
| Category | Cognitive | Cognitive |
| Legal Status | Research Only | Research Only |
| Primary Route | nasal | nasal |
| Half-life | ~5-10 minutes (but effects last hours due to downstream signaling) | ~2-3 minutes (rapid enzymatic degradation, but downstream effects persist) |
| Mol. Weight | 751.87 Da | 813.93 Da |
| Side Effects | Fatigue (mild), Nasal irritation (nasal route), Headache (rare) | Nasal irritation, Headache (rare), Dizziness (rare) |
Key differences
- Primary effect: Selank is primarily an anxiolytic (anti-anxiety) peptide; semax is primarily a cognitive enhancer and neuroprotectant.
- Derivation: Selank is a synthetic analog of the immunomodulatory peptide tuftsin; semax is a synthetic analog of ACTH(4-10), a fragment of adrenocorticotropic hormone.
- Mechanism: Selank modulates GABA, serotonin, and dopamine systems to reduce anxiety; semax upregulates BDNF (brain-derived neurotrophic factor) and modulates the melanocortin system.
- Regulatory status: Both are approved as prescription medications in Russia; neither is FDA-approved in the United States.
- Route of administration: Both are most commonly administered as nasal sprays, though subcutaneous injection is also used.
- Half-life: Selank has a short half-life of several minutes but prolonged effects due to downstream signaling; semax has a similarly short half-life with effects lasting 4–6 hours.
- Immune effects: Selank has notable immunomodulatory properties (derived from tuftsin, an immune peptide); semax has minimal direct immune effects but robust neurotrophic activity.
The verdict
Selank and semax address different cognitive needs. Selank is generally chosen for anxiety reduction, stress resilience, and mood stabilization, while semax is chosen for focus, memory, and neuroprotection. Some protocols use both together for combined anxiolytic and nootropic effects. Both have prescription status in Russia with published clinical data, but neither is FDA-approved.
Frequently asked questions
Some protocols combine selank and semax to address both anxiety and cognitive performance simultaneously, as their mechanisms do not directly conflict. Both are commonly administered as nasal sprays. No controlled studies have specifically evaluated this combination.
Selank is specifically designed as an anxiolytic peptide and modulates GABA and serotonin systems to reduce anxiety. Semax is primarily a cognitive enhancer. For anxiety-focused protocols, selank is the more targeted choice.
Semax is the more targeted choice for focus and memory. It upregulates BDNF and modulates the melanocortin system, both of which are directly involved in learning, memory consolidation, and neuroprotection.
Neither selank nor semax is FDA-approved in the United States. Both are approved prescription medications in Russia. In the US, they have been available as research compounds; regulatory status may vary and should be verified.
Both peptides are most commonly administered as nasal sprays, which allows rapid absorption through the nasal mucosa. Subcutaneous injection is an alternative route. Nasal administration is preferred for convenience and direct CNS access.