--- title: "P-21 vs Semax: Side-by-Side Comparison (2026)" url: https://www.bodyhackguide.co/compare/p-21-vs-semax description: "Compare P-21 vs Semax side by side. We earn a commission on some vendor links. Mechanism, half-life, dose range, side effects and prices. P-21 from $59.99." lang: en --- Skip to content Compare notes on r/BodyHackGuide (https://reddit.com/r/bodyhackguide) Compare notes with other researchers. Join r/BodyHackGuide (https://reddit.com/r/bodyhackguide) # P-21 vs Semax Side-by-side comparison of P-21 and Semax: mechanism, half-life, dose range, safety profile, and vendor pricing. P-21 from $59.99 Semax from $32.90 ## Price snapshot ### P-21 Current low $59.99 current listings 7-day low — not enough history yet 30-day low — not enough history yet 30-day change — not enough history yet ### Semax Current low $32.90 current listings 7-day low — not enough history yet 30-day low — not enough history yet 30-day change — not enough history yet ## P-21 P-21 (also written P021, or Peptide 021) is a synthetic peptidergic compound derived from the neurotrophic region of ciliary neurotrophic factor (CNTF), designed to activate neurogenic and BDNF-producing pathways in the… **Lowest listed price:** $59.99 across 1 listing Full P-21 profile (https://www.bodyhackguide.co/compound/p-21) ## Semax Semax is a synthetic heptapeptide (Met-Glu-His-Phe-Pro-Gly-Pro, MEHFPGP, 813 Da molecular weight) developed at the Institute of Molecular Genetics of the Russian Academy of Sciences in the 1980s. The compound is derived… **Lowest listed price:** $32.90 across 5 listings Full Semax profile (https://www.bodyhackguide.co/compound/semax) ## Side-by-side comparison | Attribute | P-21 | Semax | | --- | --- | --- | | Category | Nootropics | Nootropics | | Research Stage | Preclinical | Approved (Russia, since mid-1990s for stroke and cognitive disorders) | | Mechanism of Action | P-21 is designed to engage a subset of CNTF's biological activity — specifically the neurogenic and BDNF-inducing effects — while avoiding the JAK/STAT3 activation on peripheral CNTF receptors that causes cachexia and muscle wasting when full-length CNTF is… | Primary Mechanism: Multi-Pathway Neurotrophic Activation Semax produces its effects through coordinated activation of multiple neurotrophic, neurotransmitter, and neuroprotective pathways. Unlike conventional nootropics that target a single system (modafinil… | | Half-Life | — | ~2-3 minutes plasma half-life (functional neurological effects persist 12-24 hours due to BDNF/NGF gene expression changes) | | Typical Dose Range | 500-2000 mcg (0.5-2 mg) daily, most commonly 500-1000 mcg (community/self-experimentation range; no clinical validation) | 100-900 mcg intranasal daily (0.1% solution: 2-3 drops per nostril 2-3x daily); 1% solution used for acute stroke in Russian clinical protocols | | Dosing Frequency | Once daily (some users divide into twice daily), typically dosed in the morning | Intranasal 1–3 times daily | | Administration | — | Intranasal | | Side Effects | The side effect profile of P-21 in humans is not documented because no clinical trials have been conducted. Rodent studies describe generally acceptable tolerability at doses producing cognitive and neurogenic effects, without obvious signs of weight loss,… | Overall Safety Profile Semax has an excellent safety profile across 20+ years of Russian clinical use. In acute stroke trials, cognitive studies, and pediatric applications, Semax has demonstrated consistent tolerability with minimal adverse event burden. This… | | Molecular Weight | 578.67 g/mol (C27H42N6O8) | 813.9 Da | | Common Vial Sizes | — | 5mg, 10mg | ## Price tracking Tracking P-21 prices since September 5, 2026. Trend chart unlocks once we have price snapshots from more than one day. ## Price History 5 data points - OF - Half Nattys - Ion Peptide - BHG Labs ### P-21: potential benefits - Enhanced hippocampal neurogenesis (preclinical) - Improved learning and memory (preclinical, rodent) - Elevated BDNF and other neurotrophin expression - Neuroprotective effects in Alzheimer's disease models (preclinical) - Reduced tau hyperphosphorylation and soluble amyloid-beta in transgenic mice (preclinical) ### Semax: potential benefits - Rapid BDNF/TrkB upregulation in the hippocampus, supporting synaptic plasticity and learning (PMID: 16996037) - Neuroprotective, immunomodulatory gene-expression changes in focal cerebral ischemia (middle cerebral artery occlusion) models (PMID: 28255762) - Cognitive enhancement including improved attention, working memory, and processing speed - Dopaminergic modulation that may support motivation and executive function (preclinical data) - Stroke recovery facilitation - accelerated functional recovery and improved Barthel Index in ischemic stroke patients; approved in Russia for ischemic stroke (PMID: 29798983) - Anxiolytic and anti-asthenic effects reported in Russian clinical use, attributed to neurotrophic and monoaminergic modulation - Non-addictive cognitive support without tolerance development or withdrawal at standard doses ## Frequently asked ### What's the difference between P-21 and Semax? P-21 is a nootropics that p-21 is designed to engage a subset of cntf's biological activity — specifically the neurogenic and bdnf-inducing effects — while avoiding the jak/stat3 activation on peripheral…. Semax is a nootropics that primary mechanism: multi-pathway neurotrophic activation semax produces its effects through coordinated activation of multiple neurotrophic, neurotransmitter, and neuroprotective…. The two differ in mechanism, half-life (not reported vs ~2-3 minutes plasma half-life (functional neurological effects persist 12-24 hours due to BDNF/NGF gene expression changes)), and typical dose range. ### Which has the longer half-life, P-21 or Semax? P-21 has a half-life of not reported. Semax has a half-life of ~2-3 minutes plasma half-life (functional neurological effects persist 12-24 hours due to BDNF/NGF gene expression changes). Longer half-lives generally mean less frequent dosing but slower on/off kinetics. ### Which is cheaper, P-21 or Semax? Lowest listed price on BodyHackGuide: P-21 from $59.99, Semax from $32.90. Prices are pulled from the vendor listings tracked on BHG and change frequently. See the compare tables on each compound page for the current set of offers. ### Can you stack P-21 and Semax? Stacking depends on mechanism overlap, safety profile, and goals. P-21 and Semax should only be stacked after reviewing each compound's individual protocol page, side effect profile, and any published interaction data. Use the BodyHackGuide stack builder for a structured review before combining research compounds. ## See current vendor prices Listings from the vendors we track. Prices change often, so check the vendor before you buy. P-21 prices: https://www.bodyhackguide.co/compound/p-21?tab=prices Semax prices: https://www.bodyhackguide.co/compound/semax?tab=prices Compare all compounds: https://www.bodyhackguide.co/compare ### Before you buy P-21 or Semax Check the vendor trust score. Every supplier we track is rated 0-100 on COA verification, payment transparency, shipping, reviews, and listings: one published, reproducible methodology, applied to every vendor. View Vendor Scorecard (https://www.bodyhackguide.co/vendors/scorecard) ## Related comparisons Selank vs Semax: https://www.bodyhackguide.co/compare/selank-vs-semax **Research use only.** BodyHackGuide is a research and price-comparison reference. The compounds discussed on this page are not approved by the FDA for human consumption and are sold strictly for laboratory research. Prices shown are pulled from vendor listings tracked on BHG and are subject to change. We earn an affiliate commission on some outbound clicks, and every vendor is ranked on the same public, reproducible methodology. See editorial standards (https://www.bodyhackguide.co/editorial-standards) and affiliate disclosure (https://www.bodyhackguide.co/affiliate-disclosure). 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