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Best Peptides for Cognitive Function: What Evidence Exists
Do semax or selank improve memory or focus? What FDA reviewed, what studies in people exist, how Russia's registration differs from U.S. evidence.
The short answer
Among the peptides we reviewed, semax and selank, we found no good human evidence of better memory, focus or other cognitive function in healthy people or in people with a cognitive condition. We did not review other peptides or approved treatments for cognitive conditions. Semax and selank are not FDA-approved. FDA reviewed semax for three other uses (cerebral ischemia, migraine and trigeminal neuralgia) and found insufficient evidence of effectiveness for all three. For selank, we found rat studies and one small brain-imaging study in healthy volunteers, not a clinical trial.
That is the finding. It is not proof that these peptides do nothing. It means the evidence we could read does not show that they work for cognition.
On this page
“Nootropic” peptides are sold on the promise of sharper memory and focus. The research behind that promise is thin, and the FDA review we found did not look at memory or focus at all.
The ranking, by strength of evidence
| Peptide | U.S. status | Strongest evidence |
|---|---|---|
| 1. Semax | Limited human data | |
| 2. Selank | Limited human data |
How do we decide what is “best”?
“Best” means best evidence, not best marketing. We rank by the type of evidence first, then its quality and its result. A rank isn’t a recommendation. See how we rate peptides. For cognition, strong evidence would be a randomized, controlled trial in people that measured memory, attention or daily function, not only a brain scan or a lab value. Neither peptide has one that we could find.
Is semax approved, and what does “registered in Russia” mean?
Semax is not FDA-approved. FDA says it is a registered drug in Russia, sold as nasal drops. That is a different country’s registration, not U.S. approval and not evidence reviewed by FDA.
FDA reviewed semax for cerebral ischemia (reduced blood flow to the brain), migraine and trigeminal neuralgia. It did not evaluate semax for memory or concentration. It also did not consider seven articles in Russian on ischemia, because they lacked complete references in English. Those articles may contain evidence that neither FDA nor we evaluated. So the careful statement is not “no evidence exists” but “FDA found insufficient evidence in what it reviewed.”
What studies of semax exist in people?
| Type | Study | People | What was found |
|---|---|---|---|
| Open-label, no comparison group | Koroleva 1996, pain | 37 | Migraine pain stopped in 4 of 12; no change in typical neuralgia. FDA described it as not effective for most |
| Conference abstract | Cherkasova 2002, chronic ischemia | not stated | Changes in blood-clotting lab tests; no measure of brain function |
| Healthy volunteers | Kaplan 1996; Lebedeva 2018; Panikratova 2020 | 19, 14, 14 | Healthy people, so they don’t test treating a condition; the last two may include the same participants |
| Abstracts | Children with depression, tics; an ulcer study | 120, 331, 32 | Incomplete information; sometimes combined with other treatments |
| Animal | Rats | — | Reaches the brain through the nose; breaks down quickly |
Source: FDA presentations and briefing document. We read these studies through FDA’s description, not the originals. FDA concluded there is “insufficient evidence of effectiveness” for the three uses it reviewed. A search of ClinicalTrials.gov for semax returned no studies.
What studies of selank exist?
We found no randomized trial of selank with a clinical result that we could read, and we did not find an FDA review of it like the one for semax.
- Human imaging (marker only): a study of resting brain connectivity in 52 healthy volunteers compared selank with semax and placebo. A scan result is a marker, not a measure of memory or anxiety.
- Animals: studies in rats reported fewer signs of morphine withdrawal, less stress-related liver damage and changes in GABA-related genes (2022, 2019, 2016). Results in rats don’t carry over reliably to people.
- Comparisons with other drugs: an article from 2016 claims clinical similarity to benzodiazepines, but we saw no data for it, and we don’t treat it as evidence.
We searched PubMed in a limited way and did not read Russian-language literature, so more may exist.
Where do the regulators stand?
- Semax: on Oct. 30, 2026, HHS published an interim policy saying it does not intend to take enforcement action against certain compounding of semax, limited to the free-base form given as a nasal product, under conditions. It does not cover the acetate form or injection. This is not FDA approval, and it does not mean semax works for cognition. FDA does not review compounded drugs for safety, effectiveness or quality before they are marketed. FDA’s drug center proposed not adding semax to the compounding list, and its advisory committee voted 8–5–1 in favor of listing it (law-firm account, secondary source).
- Selank: it is not among the six peptides in HHS’s policy, and we did not find an FDA approval. FDA lists selank acetate among substances whose nominations were withdrawn, and says it may pose a risk of immune reactions for certain routes. We did not find it on FDA’s 503A Category 1 list or 503B list. We make no claim here about whether it can legally be compounded.
- Before the policy was issued, boards in Alabama and Mississippi told licensees they may not compound, administer or dispense non-FDA-approved or research-grade peptides. We found no update from them as of Oct. 31, and it isn’t clear how those notices apply to compounding under the HHS policy.
Where do HHS and FDA’s reviewers disagree on semax?
We present both and do not choose.
| Question | HHS (policy) | FDA (documents above) |
|---|---|---|
| Safety record | “several hundred subjects with no reported adverse outcome” | Safety data insufficient; abstracts incomplete; one adverse event report involved hospitalization |
| Bleeding and abuse concerns | They “have no clinical counterpart” | Not studied enough to rule out; absence of evidence is not absence of risk |
| Route | Covers only the nasal form | Evaluated the proposed nasal spray and subcutaneous injection |
What are the risks?
- Semax: FDA says safety is “insufficient” by the nasal route, with no data by subcutaneous injection and no human pharmacokinetic data. It raised a concern about a possible antithrombotic effect, which is based on lab changes in an abstract and on rat data; FDA did not describe bleeding cases in what we read. FDA also notes that no studies clarify whether it is reinforcing or addictive. An adverse event report from May 2025 described eye pain and burning after using nasal drops bought online, with hospitalization and symptoms lasting at least a year; FDA notes that this reporting system has limitations.
- Selank: FDA says it “lacks important information regarding any safety issues raised by selank acetate administered to humans” (FDA). We found no data on long-term safety, interactions or dependence.
- Both: FDA says each may pose a risk of immune reactions for certain routes; for semax, it cites injection and nasal spray.
Which claims are not supported?
- “Clinically proven nootropic” or “boosts memory and focus.” FDA did not evaluate semax for that, and we found no controlled trial.
- “Approved in Russia, so it’s proven.” A registration in another country is not evidence reviewed by FDA.
- “Safer than benzodiazepines.” We saw no trial that supports it.
- “Selank is covered by the new HHS policy.” It is not.
- “No side effects.” Not shown.
What should you ask your doctor?
- What is behind my concern about memory or focus (sleep, medicines, mood, health conditions), and what are the evidence-based options?
- If a peptide is suggested, what human evidence supports it for my goal, and who prepares it?
- Could it interact with medicines I take, especially those that affect bleeding?
We do not give doses, cycles or preparation instructions, and we do not recommend products or sellers.
Frequently asked questions
Do any peptides improve memory?
Among the peptides we reviewed, semax and selank, we found no good human evidence that they do. We did not review others.
Is semax FDA-approved?
No. FDA says it is a registered drug in Russia, which is not U.S. approval.
Is selank covered by the HHS policy?
No. The Oct. 30, 2026 policy names six peptides, and selank is not one of them.
Does semax improve focus?
FDA did not evaluate it for focus or memory, and we found no controlled trial showing that it does.
How did we rank them?
We rank by the type of evidence first, then its quality and its result. If no peptide has good evidence for a goal, we say so.
- Human trialsControlled trials in people, published in a journal, that tested a clinical outcome and showed a benefit. The strongest kind of evidence we report.
- Limited human dataSmall, short or inconclusive human studies, including observational studies, uncontrolled trials and controlled trials that did not show a clinical benefit.
- Animal studiesResults in animals often don’t carry over to people.
- Lab studiesCells or tissue in a dish. An early signal, not an answer.
Sources we checked
- FDA presentations to the Pharmacy Compounding Advisory Committee on semax (July 24, 2026)FDA. Accessed .
- FDA briefing document on semaxFDA. Accessed .
- FDA: bulk drug substances that may present significant safety risksFDA. Accessed .
- Selank and semax effects on resting brain connectivity in healthy volunteers (PubMed)PubMed. Accessed .
- Selank in rats, 2022 (PubMed)PubMed. Accessed .
- Selank in rats, 2019 (PubMed)PubMed. Accessed .
- Selank in rats, 2016 (PubMed)PubMed. Accessed .
- Federal Register: HHS enforcement discretion policy on 503A peptide compounding (Oct. 30, 2026)Other. Accessed .
- HHS: Enforcement Discretion Policy, with Appendices A and BOther. Accessed .
- McDermott+: PCAC votes on peptides (secondary source)Other. Accessed .
- Alabama Board of Medical Examiners: notice on prescribing non-FDA-approved research-grade peptidesOther. Accessed .
- Mississippi nursing, pharmacy and medical licensure boards: joint statement on peptides (Aug. 19, 2026)Other. Accessed .
- FDA 503A Category 1 list (updated May 14, 2026)FDA. Accessed .
- FDA 503B list of bulk drug substancesFDA. Accessed .
Written and maintained by the Best Peptides For Editorial Team. How we rate evidence.