N-Acetyl Selank vs Semax
A neutral, side-by-side comparison of two nootropic & cognitive peptides — their mechanisms, dosing ranges, administration routes, side effects, and research evidence. For research and educational purposes only.
N-Acetyl Selank
Acetylated variant of Selank with enhanced stability and bioavailability. The N-acetyl modification protects the peptide from rapid enzymatic degradation, extending its active half-life relative to standard Selank. Provides anxiolytic, nootropic, and immunomodulatory effects comparable to or exceeding standard Selank with potentially greater duration from each dose.
Full profileSemax
Semax is a synthetic heptapeptide derived from adrenocorticotropic hormone (ACTH) — specifically the 4–7 fragment modified with a C-terminal Pro-Gly-Pro extension for stability. Developed in Russia in the 1980s and used clinically there for stroke recovery, cognitive enhancement, and neuroprotection, it is one of the most researched nootropic peptides with a decades-long safety record in Eastern European clinical practice. Its primary mechanism involves potent upregulation of BDNF (Brain-Derived Neurotrophic Factor).
Full profile| N-Acetyl Selank | Semax | |
|---|---|---|
| Category | Nootropic & Cognitive | Nootropic & Cognitive |
| Also known as | Selank-A, N-Ac-Selank, acetylated selank, N-acetyl selank | ACTH(4-7)PGP, Met-Glu-His-Phe-Pro-Gly-Pro |
| Evidence | Research-stage | Investigational (in trials) |
| Dosing range | 100mcg–500mcg mcg, 1–2x daily intranasal | 200mcg–900mcg mcg, Once or twice daily (intranasal most common) |
| Administration | Intranasal spray, Subcutaneous injection | Intranasal (preferred — high CNS bioavailability), Subcutaneous injection |
| Key side effects | Mild sedation (acute), Fatigue, Headache (rare), Nasal irritation (intranasal route) | Mild anxiety or restlessness at high doses, Nasal irritation (intranasal route), Increased energy / difficulty sleeping if dosed too late in the day, Mild appetite suppression |
| Cited sources | 2 references | 3 references |
Key differences
- Evidence level differs: N-Acetyl Selank is research-stage, while Semax is investigational (in trials).
- Administration: N-Acetyl Selank — Intranasal spray, Subcutaneous injection; Semax — Intranasal (preferred — high CNS bioavailability), Subcutaneous injection.
- Frequency: N-Acetyl Selank is typically 1–2x daily intranasal; Semax is Once or twice daily (intranasal most common).
- Research depth: this profile cites 2 sources for N-Acetyl Selank vs 3 for Semax.
How each works
N-Acetyl Selank
N-Acetyl Selank shares Selank's core mechanism — BDNF/NGF upregulation, enkephalinase inhibition, and GABA-A receptor complex modulation — with improved metabolic stability from the N-terminal acetyl group. The acetyl modification protects against aminopeptidase N and angiotensin-converting enzyme cleavage, extending the peptide's active residence time in neural tissue after intranasal administration.
Semax
Semax increases BDNF expression in the hippocampus and frontal cortex by 1.3–1.6x at research doses in rodent models. It also upregulates NGF (nerve growth factor) and modulates serotonin, dopamine, and NMDA receptor systems. Russian clinical data (not yet replicated in Western trials) suggests efficacy in ischemic stroke recovery, ADHD, glaucoma, and cognitive decline. The Pro-Gly-Pro C-terminal extension dramatically improves resistance to enzymatic degradation compared to native ACTH(4-7).
This comparison aggregates public research and structured profile data for informational purposes only. It is not medical advice and does not recommend either compound for human use. Consult a qualified healthcare provider before considering any peptide.