N-Acetyl Semax 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 Semax
N-Acetyl Semax is the acetylated form of Semax — an N-terminal acetyl group added to the standard Semax heptapeptide. The modification significantly improves resistance to aminopeptidases, extending the active half-life and producing a more sustained cognitive effect at lower doses. Considered by many researchers to be the preferred form of Semax for neurotrophin upregulation and focus enhancement.
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 Semax | Semax | |
|---|---|---|
| Category | Nootropic & Cognitive | Nootropic & Cognitive |
| Also known as | NA-Semax, Acetyl-Semax, N-Ac-MEHFPGP | ACTH(4-7)PGP, Met-Glu-His-Phe-Pro-Gly-Pro |
| Evidence | Research-stage | Investigational (in trials) |
| Dosing range | 100mcg–600mcg mcg, Once daily (intranasal preferred) | 200mcg–900mcg mcg, Once or twice daily (intranasal most common) |
| Administration | Intranasal (preferred), Subcutaneous injection | Intranasal (preferred — high CNS bioavailability), Subcutaneous injection |
| Key side effects | Mild anxiety or over-stimulation at high doses, Nasal irritation (intranasal), Difficulty sleeping if dosed late in the day (more stimulating than standard Semax), Mild appetite suppression | 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 Semax is research-stage, while Semax is investigational (in trials).
- Administration: N-Acetyl Semax — Intranasal (preferred), Subcutaneous injection; Semax — Intranasal (preferred — high CNS bioavailability), Subcutaneous injection.
- Frequency: N-Acetyl Semax is typically Once daily (intranasal preferred); Semax is Once or twice daily (intranasal most common).
- Research depth: this profile cites 2 sources for N-Acetyl Semax vs 3 for Semax.
How each works
N-Acetyl Semax
Acetylation of the N-terminus blocks aminopeptidase cleavage at the most vulnerable site on the Semax molecule, extending its effective duration in biological fluids. Studies comparing acetylated vs non-acetylated ACTH fragment analogs consistently show greater stability and sustained receptor engagement with acetylated forms. N-Acetyl Semax demonstrates the same core BDNF/NGF upregulating and neuroprotective profile as Semax with reported greater potency per mcg due to improved bioavailability.
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.