P21
P021 / CNTF-derived peptide / Neurotrophic peptide P21
A small CNTF (Ciliary Neurotrophic Factor)-derived peptide that enhances neurogenesis and reduces neurodegeneration without the adverse effects of full CNTF (weight loss, antibody formation). P21 promotes BDNF expression, increases dendritic branching and synaptic density, and inhibits the anti-neurogenic factor leukemia inhibitory factor (LIF). Developed at the INGE Research Institute for Alzheimer's disease prevention.
Half-life
~2–4 hours
Typical Dose
500–1000 mcg/day intranasal
600/1000Route
intranasal
Category
neuroprotective
Evidence Overview
Strength of evidence across clinical, expert, and experimental lanes.
How P21 is dosed in practice
Usually taken as a nasal spray. Typical range: 500–1000 mcg/day intranasal. Half-life: ~2–4 hours. Each card gives the dose, frequency and duration from one evidence lane: Clinical (human trials), Expert (practitioner protocols) or Experimental (early or animal data). These ranges describe what has been studied or used; they are not a prescription.
Work out the units to draw with the reconstitution calculator, how long a vial lasts with the vial duration calculator, and how levels fall between doses with the half-life calculator.
Growing community interest for cognitive enhancement and neuroprotection. Users report improved memory consolidation, vivid dreams, and enhanced learning ability. Often combined with other nootropic peptides. Limited long-term safety data in humans.
- Reddit r/Nootropics — P21 user experience reports
- Longecity forum — P21 cognitive enhancement protocols
- N=1 biohacking experiments with cognitive testing
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Upgrade to ProSafety & Contraindications
- Active cancer affecting the CNS (promotes neuronal growth)
- Pregnancy or breastfeeding
- Concurrent high-dose lithium use (both affect GSK-3β pathway)
P21: common questions
What is P21?
A small CNTF (Ciliary Neurotrophic Factor)-derived peptide that enhances neurogenesis and reduces neurodegeneration without the adverse effects of full CNTF (weight loss, antibody formation). P21 promotes BDNF expression, increases dendritic branching and synaptic density, and inhibits the anti-neurogenic factor leukemia inhibitory factor (LIF). Developed at the INGE Research Institute for Alzheimer's disease prevention.
How is P21 dosed?
P21 is usually taken as a nasal spray. Typical range in DoseCraft's library: 500–1000 mcg/day intranasal. Experimental (early or animal data): 500–1000 mcg/day intranasal; Once daily, typically morning; 4–8 week cycles. These ranges describe what has been studied or used; they are not a prescription.
Is P21 FDA-approved?
No. P21 is not approved by the FDA for any use in people.
What is the half-life of P21?
DoseCraft's library lists a half-life of ~2–4 hours. Half-life sets how often a compound is dosed and how long it takes to clear: about five half-lives.
Who should not use P21?
Listed contraindications: Active cancer affecting the CNS (promotes neuronal growth); Pregnancy or breastfeeding; Concurrent high-dose lithium use (both affect GSK-3β pathway).
Information is for educational purposes only. Always consult a licensed healthcare provider before starting any peptide regimen.
Page updated . How we grade evidence: methodology.