Dihexa vs N-Acetyl 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.
Dihexa
Dihexa is a synthetic hexapeptide derived from angiotensin IV, developed at Washington State University. It is considered one of the most potent nootropic peptides known — in rodent models it outperforms BDNF itself for synaptogenesis and cognitive enhancement, acting through the hepatocyte growth factor (HGF) / c-Met receptor system. Unlike most nootropics, Dihexa is highly lipophilic and can be administered transdermally or orally.
Full profileN-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 profile| Dihexa | N-Acetyl Semax | |
|---|---|---|
| Category | Nootropic & Cognitive | Nootropic & Cognitive |
| Also known as | PNB-0408, N-hexanoic-Tyr-Ile-(6) aminohexanoic amide | NA-Semax, Acetyl-Semax, N-Ac-MEHFPGP |
| Evidence | Preclinical only | Research-stage |
| Dosing range | 10mg–20mg mg, Once daily (or every other day — long-lasting effects) | 100mcg–600mcg mcg, Once daily (intranasal preferred) |
| Administration | Oral (capsule), Transdermal (cream/lotion — lipophilicity makes this effective), Subcutaneous injection (less common) | Intranasal (preferred), Subcutaneous injection |
| Key side effects | Potential for pro-proliferative effects — HGF/c-Met pathway promotes cell growth (theoretical cancer concern at high doses), Headache (uncommon), Mental fatigue if overdosed, Long half-life means effects accumulate — take every other day initially | 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 |
| Cited sources | 2 references | 2 references |
Key differences
- Evidence level differs: Dihexa is preclinical only, while N-Acetyl Semax is research-stage.
- Administration: Dihexa — Oral (capsule), Transdermal (cream/lotion — lipophilicity makes this effective), Subcutaneous injection (less common); N-Acetyl Semax — Intranasal (preferred), Subcutaneous injection.
- Dosing units differ: Dihexa is dosed in mg, N-Acetyl Semax in mcg — they operate at different scales.
- Frequency: Dihexa is typically Once daily (or every other day — long-lasting effects); N-Acetyl Semax is Once daily (intranasal preferred).
How each works
Dihexa
Dihexa (PNB-0408) was developed by Joseph Harding and colleagues at WSU as a metabolically stable angiotensin IV analog. It binds hepatocyte growth factor (HGF), potentiating its interaction with the c-Met receptor — a pathway critical for dendritic branching, synapse formation, and synaptic plasticity. In rodent Alzheimer's and scopolamine-impaired models, Dihexa restored cognitive performance at doses ~7 orders of magnitude lower than BDNF. It readily crosses the blood-brain barrier due to its lipophilicity, unlike BDNF itself.
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.
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.