Head to head
Dihexa vs Selank
A comparison decided mostly by evidence: Selank has been studied in people to a degree the other has not.
Verdict
One has been tested in people; the other has not
What you are actually choosing between
Both are classed here as nootropics, so this is a within-class choice: the mechanism is broadly shared and what separates them is kinetics, route, and how much has actually been tested.
The overlap is focus and cognition. On this site's goal weighting — an editorial priority score, not a measure of effect size — Dihexa rates 5/5 for focus and cognition and Selank rates 3/5. Outside that overlap only Selank goes further, carrying weight for recovery and sleep; Dihexa's declared goals stop at the overlap.
The evidence
This is the part that decides most of it. Selank has approval from a regulator somewhere, though not a current FDA or EMA label — a registered Russian medicine; the trials are small and Russian-language. Dihexa has animal and cell data only, and no controlled human dosing trials — there is essentially no human data at all. That gap is the headline, and it is a statement about the literature rather than a promise about you: a compound with trial data can still do nothing for your case, and one without it is unproven rather than disproven.
How they differ in practice
Dihexa is taken by mouth and applied to the skin; Selank is a nasal spray and a subcutaneous injection. Neither one forces you onto a needle.
No half-life is published for either compound in this dataset. That absence is itself information: it means the pharmacokinetics have not been characterized well enough to quote, so both dosing schedules — once daily for Dihexa, twice daily for Selank — are convention.
Committed time differs: Dihexa runs 4 weeks, Selank runs 2 weeks.
Risk and difficulty
The contraindication lists are not the same: Dihexa flags active malignancy, which Selank does not. If any of those describe you they remove a compound from consideration outright, regardless of everything above.
Selank is rated intermediate here and Dihexa advanced. That rating is about how much can go wrong in handling, dosing and monitoring, not about how well either works.
Source notes
What the evidence actually says
Verbatim, so you can check the verdict above against what it was built from.
Dihexa
THERE IS ESSENTIALLY NO HUMAN DATA ON DIHEXA. It is a small-molecule angiotensin IV analogue developed in an academic laboratory (Washington State University) that potentiates hepatocyte growth factor signaling at its receptor c-Met and promotes synaptogenesis. Every efficacy claim attached to it comes from rodent work: scopolamine-impaired and lesioned rats, and Parkinson and Alzheimer disease models. It has never completed a published human trial, there is no published human pharmacokinetic or toxicology data, and no approved product exists anywhere. Because of that, the range given here is deliberately narrow and conservative: it is derived from what unregulated users report taking (roughly 3-20 mg per day orally or transdermally), NOT from any dose-finding study, and it should be read as a description of practice, not a recommendation. The active-malignancy flag is not a formality: c-Met is a well-characterized oncogenic pathway and chronically potentiating it in a person with an existing or suspected cancer is a real theoretical hazard. It is taken as a powder or in a carrier rather than reconstituted for injection, so the vial and bacteriostatic water fields do not apply in the usual way.
Selank
A synthetic heptapeptide analogue of the immune peptide tuftsin, again with a Pro-Gly-Pro tail added for stability. Its character is anxiolytic rather than stimulant, which is why it is usually paired with, not substituted for, Semax. Like Semax it is a Russian-registered intranasal medicine (commonly a 0.15% solution) and is NOT approved in the US or EU; the human evidence is small Russian trials in generalised anxiety disorder and adjustment disorder, some comparing it against benzodiazepines such as phenazepam, and it has not been independently replicated in Western trials. Route matters: it is an intranasal drug, not an injectable. Russian clinical dosing runs to roughly 1800-2700 mcg per day divided across two or three administrations; the per-dose range here reflects the more conservative doses typical of non-clinical use rather than the full trial daily total. Plasma half-life is minutes, so no hourly figure is listed. Courses are conventionally short (10-14 days) rather than continuous.
Side by side
The numbers
| Attribute | Dihexa | Selank |
|---|---|---|
| Class | Nootropic | Nootropic |
| Routes | Oral, Topical | Intranasal, Subcutaneous |
| Dose range | 3 mg–10 mg (typical 5 mg) | 150 mcg–900 mcg (typical 300 mcg) |
| Frequency | Once daily | Twice daily |
| Half-life | Not characterized | Not characterized |
| Cycle length | 4 weeks | 2 weeks |
| Experience | Advanced | Intermediate |
| Evidence | Animal / cell data only | Approved elsewhere |
| Contraindications |
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| Side effects |
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Turn a typical dose into a mark on the syringe: Selank
Goals
Where they overlap, and where they do not
| Goal | Dihexa | Selank |
|---|---|---|
| focus and cognition | Dihexa: 5/5 | Selank: 3/5 |
| neuroprotection | Dihexa: 4/5 | Selank: 2/5 |
| recovery and sleepone only | Dihexa: — | Selank: 4/5 |
| immune supportone only | Dihexa: — | Selank: 2/5 |
They overlap on 2 goals and diverge on 2. Weights are this site’s editorial priority score out of 5 — how central a goal is to why people use a compound. They are not effect sizes and two 5s do not mean two equal results.
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Educational information only, not medical advice. Talk to a licensed clinician before starting, changing, or stopping anything.