P21 vs Semax & Selank
A detailed comparison to help you understand the differences and choose the right peptide for your research goals.
P21
P21 is a synthetic peptide derived from Cerebrolysin, specifically designed to mimic the neurotrophic effects of the parent compound. It promotes neurogenesis and has shown cognitive-enhancing properties in research.
Full details →Semax & Selank
A nootropic combination pairing two Russian-developed peptides for cognitive enhancement. Semax provides stimulating focus and neuroprotection while Selank offers anxiolytic and mood-stabilizing effects, creating a balanced cognitive enhancement stack.
Full details →Side-by-Side Comparison
| Aspect | P21 | Semax & Selank |
|---|---|---|
| Mechanism | Inhibits glycogen synthase kinase-3β (GSK-3β) and activates CREB signaling pathway. This promotes BDNF expression, neurogenesis in the hippocampus, and synaptic plasticity. | Semax enhances BDNF expression and modulates dopamine and serotonin systems for improved focus, memory, and neuroprotection. Selank affects BDNF and GABA systems, providing anxiolytic effects and immune modulation. Together they support cognitive function while managing stress and anxiety. |
| Typical Dosage | Research protocols typically use 1-5mg administered intranasally or subcutaneously. Often used in cycles of 2-4 weeks. | Semax: 200-600mcg intranasally 2-3 times daily. Selank: 250-500mcg intranasally 2-3 times daily. Can be used together or alternated based on needs. |
| Administration | Can be administered intranasally for direct CNS access or subcutaneously. Best used cyclically rather than continuously. | Primarily administered intranasally for rapid brain uptake. N-Acetyl versions (NA-Semax, NA-Selank) offer enhanced stability and potency. Can also be injected subcutaneously. |
| Side Effects | Limited data. Reported effects include mild headache, temporary brain fog during initial use, and fatigue. | Semax may cause mild irritability or hair shedding. Selank may cause mild fatigue or nasal irritation. Both are generally well-tolerated. |
| Best For |
What They Have in Common
Both P21 and Semax & Selank are commonly used for: