Updated August 2026
Selank + Semax Dosage: Research Evidence, Blend Conventions, and Study Protocol
Research note: Selank + Semax is a two-peptide combination, not a new chemical entity. No peer-reviewed human fixed-combination trial was located. Panikratova 2020 used separate groups (Selank 0.2 mg once vs Semax 1.2 mg once) — not coadministration. Proposed factorial dose: 300 mcg Selank + 300 mcg Semax intranasally × 3/day (08:00, 12:00, 16:00) × 14 days — investigator protocol, not a clinical recommendation.
Selank (TKPRPGP, ~751.9 Da) and Semax (MEHFPGP, ~813.9 Da) share a C-terminal Pro-Gly-Pro motif but differ in structure, development history, and proposed pharmacology. Combination products are commonly 1:1 by mass — not exactly equimolar (~1.08:1 Selank:Semax mole ratio at equal mass).
Parent Russian products are separate medicinal products with different concentrations and indication-specific schedules. Selank 0.15% label ≈ 900 mcg/day; Semax 0.1% lower-context regimens commonly 400–900 mcg/day. Neither creates a combination label.
Every usable dose must specify: X mcg Selank + Y mcg Semax per administration, frequency, route, duration. A “5 mg + 5 mg vial” describes inventory, not per-dose exposure.
Selank + Semax in 30 seconds
| Question | Current answer |
|---|---|
| Combination trial | None located |
| fMRI 2020 | Separate groups · not blend |
| Common ratio | 1:1 by mass (commercial) |
| Online IN range | ~50–500 mcg of each per dose |
| Proposed study dose | 300+300 mcg × 3/day × 14 d |
| Parent Selank/day | ~900 mcg (label) · 2,700 mcg (trial) |
| Parent Semax/day | 400–900 mcg (lower 0.1% context) |
| Validated SC combo | None |
Combination identity
“Selank + Semax” may mean a fixed-ratio bottle, two separate products used together, or staggered timing — not automatically equivalent. Fixed blends couple both doses and require compatibility, stability, and dual assay release.
Identity gate
Fixed blend vs separate bottles vs vial label vs ambiguous “blend dose”
Requires independent assay of each peptide per lot
One bottle with both TKPRPGP and MEHFPGP — must quantify Selank and Semax separately. HPLC % alone can hide wrong ratio.
Selank vs Semax at a glance
Dual peptide comparison
TKPRPGP vs MEHFPGP — shared PGP motif, different parent anchors
| Property | Selank | Semax |
|---|---|---|
| Sequence | TKPRPGP | MEHFPGP |
| Origin | Tuftsin analog | ACTH(4–7)-PGP analog |
| MW (free peptide) | ~751.9 Da | ~813.9 Da |
| Russian IN concentration | 0.15% (1.5 mg/mL) | 0.1% (1 mg/mL) lower-dose |
| Shared motif | C-terminal Pro-Gly-Pro | C-terminal Pro-Gly-Pro |
| Typical parent daily (lower context) | ~900 mcg/day IN | 400–900 mcg/day IN |
Equal mass is not equimolar
At 300 mcg each: Selank ≈ 0.399 µmol, Semax ≈ 0.369 µmol. True equimolar mass would require ~8.2% more Semax than Selank by free-peptide mass.
Mass vs moles
1:1 mass ≠ equimolar — 813.9/751.9 ≈ 1.08:1 at equal mcg
Selank
0.399 µmol
Semax
0.369 µmol
Molar ratio (S:X)
0.92:1
Equimolar Semax mass for 300 mcg Selank: 324.7 mcg (~8.2% more than equal mass).
Direct combination evidence status
Combination evidence
No human coadministration trial · fMRI used separate groups
- Fixed-combination human trial
- None located
- Human coadministration PK
- None located
- Pharmacodynamic synergy data
- None located
- Maximum tolerated combination dose
- Not established
- Validated SC combination dose
- None
- Authorized fixed-combination label
- None
- Comparative fMRI (separate groups)
- Selank 0.2 mg vs Semax 1.2 mg once each
Regulatory and labeled-dosage context
No authorized Selank + Semax fixed-combination product located. U.S.: neither peptide has a prescribing label; FDA July 2026 proposed Semax not be included on 503A bulks list; both selank acetate and Semax appear on compounding safety materials.
The 2020 fMRI study was not a combination trial
Panikratova et al. randomized healthy participants to separate Semax, Selank, or placebo groups with single intranasal doses before repeat resting-state fMRI. Useful for comparative parent connectivity — not combination, interaction, or synergy evidence.
Panikratova 2020
Separate Semax / Selank / placebo groups — single IN dose each
| Group | n | Exposure | Note |
|---|---|---|---|
| Semax | 14 | 1.2 mg 1% IN once | Separate group — not combination |
| Selank | 16 | 0.2 mg 0.15% IN once | Separate group — not combination |
| Placebo | 22 | 0.1% nipagin | Connectivity surrogate only |
Separate parent-product dosing anchors
Parent-product anchors
Separate Russian schedules — not combination validation
| Source | Regimen | Daily / note |
|---|---|---|
| Current Russian label | 2 drops/nostril × 3/day × 14 d | ~900 mcg/day |
| Zozulia 2008 program | 900 mcg × 3/day × 14 d | 2,700 mcg/day |
| Panikratova 2020 fMRI | 200 mcg once | Single acute exposure |
Even if dose A of Selank and dose B of Semax were each used independently, A + B is not validated for safety, efficacy, or optimal ratio without factorial study.
Evidence hierarchy
Evidence hierarchy
Parent labels moderate · combination inference very low
- Authorized combo label
- None
- Human combination trial
- None located
- Comparative fMRI
- Separate groups only
- Parent products
- Selank ~900 mcg/day · Semax 400–900 mcg/day
- Commercial 1:1 blends
- Convention only
Commonly reported combination protocols
Reported conventions
50–500 mcg each · 1:1 mass common · definitions vary
- Selank
- 300 mcg
- Semax
- 300 mcg
- Frequency
- 3× daily (08:00, 12:00, 16:00)
- Route
- IN
- Duration
- 14 days
- Evidence
- Investigator protocol · not clinical dose
Cumulative exposure examples
Cumulative exposure
14-day Selank + Semax totals per peptide and combined
Selank/day
900 mcg
Semax/day
900 mcg
14-day Selank
12.60 mg
14-day Semax
12.60 mg
Parent anchors versus anecdotal blends
Evidence split
Parent IN anchors vs commercial 1:1 blend conventions
Parent-product intranasal anchors
Separate products · not combination validation
- Selank label-like
- ~900 mcg/day Selank
- Semax lower-context
- 400–900 mcg/day Semax
- Combination trial
- None located
- fMRI 2020
- Separate single-dose groups only
Commercial / community blends
50–500 mcg each · 1:1 mass common
- Typical per admin
- 100–250 mcg of each
- Fixed ratio
- 1:1 by mass (not equimolar)
- “Blend dose” ambiguity
- Total vs each peptide often unstated
- SC schedules
- No validated human combination basis
Why the proposed study uses 300 + 300 mcg three times daily
Selank 900 mcg/day approximates current Russian drop-count regimen. Semax 900 mcg/day is at the upper boundary of historical short mental-fatigue/adaptation range and below high neurologic-injury schedules. 1:1 mass matches common commercial convention. 08:00, 12:00, 16:00 avoids late-evening Semax. 14 days matches Selank short course. Factorial arms permit interaction estimation.
Preclinical evidence — mostly parallel, not combination
300 mcg/kg Selank and 50–100 mcg/kg Semax reflect separate rodent programs — not a human mass ratio or blend dose.
Safety, side effects, and monitoring
Safety monitoring
Combination safety unknown · factorial attribution required
- Combination-specific
- No adequate human fixed-combination safety dataset. Attribution of events to Selank, Semax, interaction, excipient, or impurity requires factorial arms.
- Nasal
- Combined volume/formulation may alter mucosal tolerability vs either peptide alone — burning, epistaxis, smell change.
- Neurologic / psychiatric
- Semax-associated activation vs Selank-associated calm — insomnia, agitation, sedation, mood change possible; interaction unknown.
- FDA compounding
- Both selank acetate and Semax on withdrawn bulk lists — aggregation, impurities, immunogenicity concerns for compounded material.
Fixed-blend product-quality requirements
Release must quantify Selank and Semax separately — chromatographic resolution, intact mass for each, compatibility/stability in combined formulation, delivered-dose uniformity, spray pattern, and in-use stability. Combination compatibility studies required before human fixed-blend use.
Complete proposed factorial research protocol
Part A: 24 healthy adults · 4-period crossover · placebo, Selank 300 mcg, Semax 300 mcg, combination · single dose · 7-day washout · sentinel cohort.
Part B: 160 adults · 2×2 factorial · placebo, Selank mono (900 mcg/day), Semax mono (900 mcg/day), combination (900+900 mcg/day) · 14 days · follow-up to day 42 · double-dummy preferred.
Proposed 2×2 factorial design
Part A crossover PK lead-in → Part B 4-arm 14-day trial
Part A — 24 healthy · 4-period crossover · 7-day washout
| Period | Treatment | Selank | Semax |
|---|---|---|---|
| 1 | Placebo | — | — |
| 2 | Selank 300 mcg | 300 mcg | — |
| 3 | Semax 300 mcg | — | 300 mcg |
| 4 | Combination | 300 mcg | 300 mcg |
Part B — 160 adults · 08:00 / 12:00 / 16:00 · 14 days · follow-up d42
| Arm | Schedule | Daily exposure |
|---|---|---|
| Placebo | Matched vehicle × 3/day | Placebo |
| Selank mono | 300 mcg Selank + Semax placebo × 3 | 900 S + 0 X mcg/day |
| Semax mono | Selank placebo + 300 mcg Semax × 3 | 0 S + 900 X mcg/day |
| Combination | 300 + 300 mcg × 3/day × 14 d | 900 S + 900 X mcg/day |
Double-dummy separate formulations preferred. Synergy requires prespecified Selank × Semax interaction — not baseline improvement alone.
Claims versus evidence
Claim checker
Synergy, fMRI, 1:1 ratio, vial labels, and route claims
Selank + Semax is proven synergistic
Unproven
No human coadministration trial. fMRI study used separate groups. Synergy requires factorial interaction analysis.
Dosage evidence ladder
Dosage evidence ladder
Combination maturity: very low · parent bounds only
| Tier | Evidence | Confidence |
|---|---|---|
| 1 · Fixed-combination label | None | None |
| 2 · Randomized combination trial | None located | None |
| 3 · Human PK/interaction study | None located | None |
| 4 · Parent-product labels + studies | Selank ~900–2700 mcg/day · Semax 400–900 mcg/day lower context | Moderate parent · low for combo inference |
| 5 · Comparative fMRI separate groups | 0.2 mg Selank vs 1.2 mg Semax once | Separate exposure only |
| 6 · Preclinical parallel research | 300 mcg/kg Selank · 50–100 mcg/kg Semax | Hypothesis only |
| 7 · Commercial/community blends | 50–500 mcg each · 1:1 mass | Very low |
Bottom line
Selank + Semax is a two-peptide regimen with very low combination dosing maturity. Parent-product experience bounds a cautious intranasal study design; it does not validate coadministration, 1:1 ratio, or synergy.
The highest-value next study is a four-arm factorial trial (placebo, Selank, Semax, combination) with validated dual assay, PK lead-in, and explicit interaction analysis — not extrapolation from separate fMRI groups or online vial labels.
Separate groups ≠ combination trial. Vial mg ≠ per-dose mcg. 1:1 mass ≠ equimolar ≠ optimal.
Frequently asked questions
Is there a standard Selank + Semax dose?
No. Fixed blends commonly use equal masses, but no direct human trial has established a standard dose, ideal ratio, or maximum tolerated combination exposure.
What does “200 mcg Selank + Semax” mean?
Ambiguous unless specified as 200 mcg total (e.g. 100+100) or 200 mcg of each (400 mcg total peptide).
Is a 5 mg + 5 mg vial the dose?
It is nominal vial inventory (10 mg total peptide), not per-administration exposure. Concentration, volume, and actuations define the dose.
Is 1:1 the best ratio?
Unknown. It is a commercial convention, not equimolar, and not shown biologically optimal.
Did the fMRI study combine Selank and Semax?
No. Participants were in separate Semax, Selank, or placebo groups with single doses.
Can Russian parent doses simply be added?
They can define a provisional research starting point, but addition does not prove combination safety or efficacy.
Is there a validated subcutaneous blend dose?
No. Injectable online schedules are anecdotal and not intranasal equivalents.
Why 300 + 300 mcg three times daily for 14 days?
Provisional factorial-study dose bracketing parent-product daily amounts (~900 mcg/day each) with 1:1 mass and Selank 14-day course — requires PK/tolerability lead-in.
Does the combination improve focus without anxiety?
That is a testable commercial hypothesis, not a demonstrated clinical effect.
What counts as synergy?
Combination effect exceeding the prespecified additive model in a factorial trial — not merely improvement from baseline or vs placebo without monotherapy arms.
References
Panikratova YR et al.
Functional connectomic Selank and Semax effects2020 · separate groups · PMID 32342318.
Selank manufacturer
Russian 0.15% instructionsParent Selank anchor.
Semax manufacturer
Product instruction PDFConcentration-specific regimens.
Zozulia AA et al.
Selank in GAD2,700 mcg/day program.
FDA
Semax PCAC briefing documentJuly 2026 · characterization concerns.
FDA
Bulk substance compounding safetySelank acetate and Semax.
Volkova AA et al.
Selank GABAergic genes300 mcg/kg rats.
Dolotov OV et al.
Semax BDNF/TrkB rats50 mcg/kg IN.