FDA reports that semax is a registered drug in Russia, as nasal drops. It is not FDA approved, and FDA proposed in 2026 that it not be added to the US compounding list.

Does selank improve focus?

Not shown. The human study we found measured anxiety in patients with anxiety disorders and compared it with another drug, without a placebo group.

Has dihexa been tested in people?

Not in any published study we found. FDA says there is no human exposure data for dihexa by any route.

Semax, Selank and Dihexa for Focus: The Evidence

Short answer: No peptide is approved anywhere we found for better focus or memory in healthy people. Semax is a registered drug in Russia, studied mostly in stroke patients in Russian-language papers. Selank has a 62-patient Russian anxiety study. Dihexa has only animal data, and FDA says there is no human exposure data for it. None is FDA approved.

What people discuss for cognition and focus

What people discuss, and the strongest evidence we found for this goal
Compound	Best evidence	What it shows
Semax	Small or early human studies	Registered in Russia as nasal drops. Human studies are small Russian trials in stroke patients. FDA found too little evidence to judge it for stroke and did not evaluate it for ADHD or focus.
Selank	Small or early human studies	In a 62-patient Russian study of anxiety disorders, selank and the benzodiazepine medazepam had similar anti-anxiety effects. No placebo group.
Dihexa	Animal or lab studies only	Improved memory tests in an Alzheimer mouse model. FDA says there is no human exposure data for any route.

"Animal or lab studies only" means no published human trial for this goal that we could find. Results in rats or cells often do not carry over to people. Compounds that are not FDA-approved have no tested label for dose, purity or safety.

What has semax shown in people?

Semax is a seven-amino-acid peptide built from a fragment of ACTH (a pituitary hormone) with three amino acids added. FDA notes it is a registered drug in Russia, sold as 0.1% and 1% nasal drops. Most of its research comes from a small number of Russian groups.

The human studies we could read are about stroke, not focus:

1997: 30 patients in the acute phase of an ischemic stroke got semax and were compared with 80 similar patients on usual care. The authors reported somewhat faster recovery of movement. Patients were not randomized.
2018: 110 patients in stroke rehab were split into groups with and without semax. Semax was linked to higher blood BDNF (a nerve growth protein) and better daily-function scores.

Both are in Russian. When FDA reviewed semax for the compounding list in 2026, it set aside the Russian-only stroke papers because no English translations were available, and judged the rest (one meeting abstract) insufficient evidence for stroke. It found no supporting literature for ADHD and treated "nootropic" use as part of the stroke question. FDA proposed semax not be added to the list pharmacies may compound.

Selank and dihexa

Selank is a seven-amino-acid peptide based on tuftsin, a small immune peptide, also developed in Russia. Lab work suggests it changes how GABA receptors respond, the same system that benzodiazepines act on. The main human study we found (2008, Russian) compared selank in 30 patients with medazepam in 32 patients with generalized anxiety or neurasthenia. Both reduced anxiety by similar amounts. It was not placebo-controlled, and it measured anxiety, not focus.

Dihexa is a modified form of angiotensin IV, a brain signaling peptide. In a 2021 mouse study of Alzheimer disease, it improved maze performance and lowered brain inflammation markers. FDA lists dihexa with no human exposure data for any route, so its safety in people is unknown.

Approval status

Regulatory status as found in the sources on this page.
Compound	Approved anywhere?	FDA compounding notes
Semax	Registered in Russia (nasal drops)	FDA proposed in 2026 not to add it to the 503A compounding list
Selank	Not approved in the US	Listed by FDA with possible immune reactions and missing safety information
Dihexa	Not approved anywhere we found	Listed by FDA: no human exposure data for any route

All three appear on FDA's compounding risk page in the table of substances previously in category 2 whose nominations were withdrawn. See compounding pharmacy.

Safety, and what is still unknown

No trials in healthy people for focus. We found no placebo-controlled trial showing any of these improves attention or memory in healthy adults.
Expectation effects are large. Focus and mood are easy to change with belief alone, which is why placebo groups matter.
Unknown long-term effects. FDA could not find human pharmacokinetic studies for semax, and dihexa has never been given to people in published research.
Brain fog has causes worth finding. Poor sleep, thyroid problems, low iron, depression and medicines can all cause it. A clinician can check.

This page is education, not medical advice. A clinician should diagnose the problem and make any prescription decision with you.

What is worth tracking

Doses with time of day. Nasal sprays and injections may act fast or not at all; timing is the only way to tell.
One focus rating a day. Rate focus 0-10 in the daily check-in at the same time each day, before you look at your dose log.
Sleep. Log sleep hours or a sleep score. Better sleep can explain a "focus" gain on its own. See sleep.
Side effects. Headache, irritability, anxiety, nasal irritation or trouble sleeping, each with a date.
Caffeine and other drugs. Note changes in coffee, stimulants or prescriptions, which affect focus more than most peptides plausibly could.

Terms on this page: Peptide · Compounding pharmacy · Research use only (RUO)

This page is education, not medical advice, and it is not a recommendation to use any compound. It does not cover dosing. Talk to a licensed clinician before starting, changing or stopping anything, and get diagnosed before treating a symptom.

Frequently asked questions

Sources

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