Deep dive into peptides with primary neurological benefits — protocols, evidence, and side-by-side comparison
| Cerebrolysin | Semax | Selank | NA-Selank | Dihexa | P21 | |
|---|---|---|---|---|---|---|
| Route | SubQ (community-reported) / IM | Nasal | Nasal | Nasal / SubQ | Oral / SubQ | SubQ |
| Dose Range | 1–5 mL per administration | 200–600 mcg/day | 250–750 mcg/day | 200–500 mcg/day | 5–20 mg oral, 1–5 mg subq | 1–2 mg/day |
| Cycling | 20 days on, 2–3 courses/year | 10–20 days on, 10 days off | 14–21 days on, then cycle off | Similar to Selank: 14–21 days on, cycle off | Emerging — no established protocol | 30 days on, variable off period |
| Primary Benefits | Neuroprotection, TBI recovery, neuroplasticity, neurodegenerative support (Alzheimer's) | Cognitive enhancement, BDNF upregulation, focus and memory, stroke recovery | Anxiolytic (GABA modulation), cognitive enhancement, immune modulation, stress resilience | Enhanced Selank effects, longer half-life, improved nasal absorption | Synaptogenesis, memory enhancement, HGF/c-Met pathway activation, dendritic spine density | Neurogenesis (hippocampal), BDNF increase, spatial memory improvement |
| Evidence | RCT | human-obs | human-obs | animal | animal | animal |
| Safety | Well-studied in clinical settings (IV). SubQ data limited to community reports. Injection site reactions, headache, dizziness. | Well-tolerated. Nasal irritation possible. Approved in Russia/Ukraine for clinical use. | Well-tolerated. Mild sedation at higher doses. Approved in Russia for clinical use. | Limited long-term data. Generally well-tolerated based on community reports. | CAUTION: Pro-cancer concern via HGF/c-Met pathway. No human safety data. Research chemical only. | Limited data. Generally well-tolerated in animal studies. No human clinical trials. |
Cerebrolysin is traditionally IV; subq use is community-reported. Data reflects non-IV routes where available.
Last updated: 2026-05-01