P21 vs Semax
Which should you choose? Here's what you need to know.
The short answer
P21 and Semax are both cognitive / neuro peptides, but they work differently. A synthetic peptide derived from ACTH (4-10) developed in Russia as a nootropic and neuroprotective agent. Available as a prescription nasal spray in Russia. Compare vendor pricing and availability below.
On 20 Sep 2026 Peptide Compare tracked 7 vendors selling P21, cheapest in stock $8.50 per mg at Soma Chems, and 58 selling Semax, cheapest $2.12 per mg at Biotech Peptides.
P21
Cognitive / NeuroSemax
Cognitive / NeuroA synthetic peptide derived from ACTH (4-10) developed in Russia as a nootropic and neuroprotective agent. Available as a prescription nasal spray in Russia.
Price & availability
Once you've decided which peptide fits your needs, here's how they compare on price and vendor options. Prices verified Sep 20, 2026.
P21
Semax
$84.99
Starting from
$20.00
$47.57
Avg. price per mg
$4.76
7
Vendors selling it
58
5 options
In stock now
58 options
7.0/10
Top trust score
9.1/10
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Where does this data come from?
We re-check vendor prices continuously and score vendors on Finnrick blind-test results — samples bought anonymously and sent to a lab, not vendor claims. No vendor can pay to rank higher. See our full methodology.