P21

What P21 does

P21, also called P021, copies part of CNTF, a protein that supports nerve cells. Animal findings vary, with no human study identified; human safety, brain delivery and online product identity remain uncertain. People report nasal and injected use.

• In a study in mice, months of dosing in food brought some benefits; no human study has been found. (animal)
• People report using it for clearer thinking, learning and memory, though some report no benefit. (Reported by users)
• One user reported faster thinking after a brain injury, but was also taking several other peptides at the same time. (Reported by users)

Uses in the sources

• People report using it for clarity, learning and memory. Some report no benefit. (Reported by users) (source)
• Some people use it in self-directed brain-injury stacks with Semax or Selank. No human combination benefit is established. (Reported by users) (source)

P21 dosage

Typical reported dose: 1 mg nasal spray once a day

• 1 mg nasal spray for 8 weeks: 1 mg nasal spray daily daily, nasal spray. Reported by users, rare report. Studied in: Adults posting self-experiments online; identity and product content unverified. (source)
• 500-2,000 mcg injected daily: 500 mcg up to 2 mg under the skin per day daily, under the skin. Reported by users, rare report. Studied in: Adults posting self-experiments online; identity and product content unverified. (source)

These are doses reported in labels, trials or user reports, not a personal plan. Check the source behind each one.

Work out syringe units with the dosing calculator

How to mix P21

Comes as: Powder vials reported online, Prepared or home-mixed nasal sprays reported online, Under-skin injections reported online.

Mixed with: Bacteriostatic water appears in nasal-spray discussions. This is not a validated P021 formulation..

Common vial sizes: 55 mg. Common water amounts: 10 mL.

• 55 mg with a proposed 10 mL volume comes from one preparation question. These are observed values, not established common sizes.
• The post asked about 250 mcg/spray and later 550 mcg/pump. Pump output and the finished concentration were not verified.
• Do not convert spray counts to a dose without measured pump output. A nasal preparation is not an injectable product.

Before mixing: No validated storage temperature or human-product shelf life identified.

After mixing: No validated post-mixing temperature, sterility period or expiry identified.

P21 side effects and risks

Reported side effects

• Sleepiness or overstimulated fatigue: One nasal spray user described alternating stimulation and sleepiness; no incidence estimate., moderate. Avoid driving when sleepy and review new symptoms. The report included existing sleep disorders. (source)
• Allergy or infection related to the product: General unapproved product risk; no measured P021 event rate., serious. Breathing problems or spreading injection-site infection need urgent care. (source)

Stop and get help if

• Trouble breathing, throat or tongue swelling, collapse or fainting after exposure.: Call emergency services now. These can be signs of anaphylaxis.
• A hot, painful, spreading red injection site, especially with fever or feeling very ill.: Seek urgent medical care. Confusion, fainting or fast breathing needs emergency care.

Who should avoid it

• pregnant: Precautionary block: no human pregnancy safety data. Prenatal mouse experiments do not establish fetal safety.
• breastfeeding: Precautionary block: milk transfer and infant safety have not been studied in humans.
• tryingToConceive: Precautionary block: human fertility and early-pregnancy effects are unknown.
• under18: Precautionary block: no human pediatric dose or developmental safety study identified.
• activeCancer: Growth-related signaling changes occur in lab models. Cancer safety in people is unknown; this is a precaution, not proof of cancer risk.
• cancerHistory: No human recurrence or cancer-safety data; discuss experimental growth-signaling compounds with the treating clinician.
• seizureDisorder: No human seizure safety data. The CDKL5 mouse study does not establish safety or benefit for human epilepsy.
• psychiatricCondition: No human mood or psychiatric safety study. Reports of stimulation and sleepiness warrant review.
• kidneyDisease: Human clearance and dose adjustment in kidney disease are unknown.
• liverDisease: Human metabolism and dose adjustment in liver disease are unknown.
• testedAthlete: Unapproved pharmacological substances fall under the 2026 prohibited-list rules; growth-factor rules may also apply.

Interactions

• Other nootropics, peptides and sedating substances: P021 interaction studies are absent. Stacking may add unpredictable effects; sleepiness is reported, but a specific drug interaction is unproven.

Product quality risks

• General peptide warnings describe wrong ingredients, wrong amounts and microbial or solvent contamination. No independent market survey of this compound was located.
• A purity percentage cannot establish dose, identity, sterility or clinical safety.
• Research-use labeling does not mean a product meets medicine quality standards.

What to expect

No human study identified. Ten rodent and lab papers include a mostly negative study in mice missing the CDKL5 gene and a 2026 brain-scan paper with a published correction.

Key studies

• Original P21 mouse study: Initial P21 findings were in normal adult mice. (source)
• Long oral course in Alzheimer-like mice: Long exposure in mice does not establish long-term human safety. (source)
• Learning in aged rats: Aged-rat results are not a human aging trial. (source)
• Tau in aged-rat spinal fluid: Tau changes in rats do not establish prevention of human dementia. (source)
• 18-month Alzheimer-like mouse study: Prolonged dietary exposure produced some benefits in one mouse model. (source)
• Mouse pathology and survival: Reported survival differences are specific to this mouse model. (source)

P21 FAQ

• Is P21 FDA-approved? No FDA-approved product or label found. FDA GSRS lists the substance, but UNII registration does not imply approval.
• How do people take it? Nasal spray, daily. 8 weeks. Source: reported by users, not an established dose.
• What's the difference between P21 and Semax? P21: an experimental memory peptide with animal research and no established human dose or safety profile. Semax: a Russian nasal peptide with limited human evidence for brain and nerve effects. Why people pair them: reported alongside P21 for focus and self-directed recovery.
• Can I take it with Semax or N-acetyl Semax? Reported alongside P21 for focus and self-directed recovery. Several posts mention it, but no P021 combination trial was found. Effects cannot be attributed to either compound. Source: reported by users. Ask a doctor before combining anything.
• Is it banned in sport? Yes. It is banned in and out of competition (WADA 2026). Rule-based classification of unapproved substances; neither is named. Growth-factor mimetics may fall under S2. Confirm with the anti-doping body.
• How long does a mixed vial last? No validated post-mixing temperature, sterility period or expiry identified.