Two Russian-developed peptides, frequently sold as a pair, both stabilized the same way with a Pro-Gly-Pro extension. Semax is positioned as cognitive, Selank as anxiolytic. The evidence problem is identical for both.
Side by side
| Semax | Selank | |
|---|---|---|
| Class | Nootropic heptapeptide | Anxiolytic heptapeptide |
| Status | Approved in Russia (intranasal); research compound elsewhere | Approved in Russia (intranasal); research compound elsewhere |
| Route | Intranasal (primary) or subcutaneous | Intranasal (primary) or subcutaneous |
| Typical vials | 5 mg, 10 mg | 5 mg, 10 mg |
| Dose range | 200 mcg to 600 mcg | 250 mcg to 750 mcg |
| Frequency | Daily, often split morning and midday | Daily, as needed |
| Half-life | No human data | No human data |
| Dosing unit | micrograms | micrograms |
Pharmacokinetics
No curves are shown, on purpose.
No published human pharmacokinetics for Semax or Selank. Drawing one curve against an absent one would imply a comparison that cannot be made.
What the evidence supports
These grade how well each outcome has been studied in humans, never how well either compound works. A strong grade can sit on a negative result.
Both top out at the same tier of evidence: Human RCT. Where they differ is in which outcomes have been asked about, not in how well either has been studied overall.
Semax
| Outcome | Evidence |
|---|---|
| Ischemic stroke recovery | Human RCT |
| BDNF and NGF expression | Animal only |
| Cognitive enhancement in healthy people | No data |
| Independent replication outside Russian literature | No data |
Selank
| Outcome | Evidence |
|---|---|
| Generalized anxiety disorder | Human RCT |
| Cognitive and attention measures | Human, observational |
| Independent replication outside Russian literature | No data |
How to choose
Semax is the one with stroke trials
Its strongest human evidence is in acute ischemic stroke, not in healthy cognition, which is what it is usually bought for.
Selank's comparator is the problem
Its trials compare it against a benzodiazepine that is not licensed in most countries, which makes the results hard to place against anything a reader would recognize.
Both are approved in Russia only
The literature is almost entirely Russian-language and has not been independently replicated elsewhere.
At the syringe
At the default setup on each compound's own page, a 5 mg vial in 2 mL puts 25 mcg on every insulin unit, while a 5 mg vial in 2 mL puts 25 mcg on every unit. That is the number that decides whether a dose lands on a readable mark, and it is set by how much water goes in, not by the compound.