Evidence review: Open Peptide Project (verified against primary PubMed, ClinicalTrials.gov & FDA records) · Last checked 2026-10-27. ← Back to Evidence Library
Kyotorphin (L-Tyr-L-Arg): what the evidence says
At a glance
What it is: a natural dipeptide (tyrosine-arginine) first isolated from bovine brain in 1979 that may work by releasing Met-enkephalin. R1, R2
What the evidence says: it produced morphine-like pain relief in animals when given into the brain, R3 and reviews describe a specific receptor and brain distribution. R4 Researchers have worked on derivatives because the plain dipeptide crosses into the brain poorly. R5 We found no human treatment trial.
Biggest risks: unknown in people.
Rating
| Human Human evidence | None |
| Animal Animal / lab evidence | Rodent analgesia studies R3, R4 |
| Regulatory | Not FDA-approved · not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page R6, R7, R8 · not named by WADA R9 |
| Established human dose | No |
Evidence verdict: Pain relief in people: Unknown (no human trials) · Analgesia: animal only
This page reports what studies used. It is not dosing advice.
Legend: HUMAN data · ANIMAL / LAB data · UNKNOWN · UNVERIFIED: not yet confirmed against a primary source
About the evidence: everything here is from animals or lab work. Human use is untested.
What is it?
Related pages: Dalargin, Semax, Selank, Noopept.
Does it work?
- Animal Analgesia in rodents, mostly by direct brain injection. R3, R4
- Animal Derivatives designed to cross membranes better. R5
- Unknown No human trials.
Is it safe?
- Unknown No human safety data.
Gray-market vials: extra risks
A gray-market vial has no quality control and no guarantee of identity, strength or sterility. We test retail vials blind under the Open Peptide Standard; see /tests/. A passing test covers one batch on one date and does not mean the compound is safe.
Is it legal?
- US: not FDA-approved; no Drugs@FDA application found (openFDA searched Oct 26, 2026).
- Compounding: not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page. R6, R7, R8
- Sport: not named on WADA's 2026 Prohibited List. R9
Study details
Study details
These are amounts researchers used, not recommendations.
| Study | People / model | Route | Amount used | Follow-up | Reported | Citation |
|---|---|---|---|---|---|---|
| No human studies | — | — | — | — | — | — |
Full reference list (PubMed, CT.gov, FDA and WADA checked Oct 26, 2026)
- R1 Takagi H, et al. Nature. 1979. PMID 228202
- R2 Shiomi H, et al. Neuropharmacology. 1981. PMID 7254487
- R3 Takagi H, et al. Eur J Pharmacol. 1979. PMID 436940
- R4 Ueda H. Front Med Technol. 2021. PMID 35047919
- R5 Serrano ID, et al. Biopolymers. 2015. PMID 25363470
- R6 FDA, 503A bulk drug substances categories list (updated May 14, 2026). https://www.fda.gov/media/94155/download
- R7 FDA, 503B bulk drug substances categories list (updated Mar 21, 2025). https://www.fda.gov/media/94164/download
- R8 FDA, Certain bulk drug substances for use in compounding that may present significant safety risks (content current Apr 22, 2026). https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks
- R9 WADA. The 2026 Prohibited List, full list checked; compound not named. https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf
Disclaimer
This page is for education and harm reduction, not medical advice or a recommendation to use Kyotorphin (L-Tyr-L-Arg). This compound is not FDA-approved. Any product sold under this name in the US is unregulated. Report problems to FDA MedWatch (https://www.fda.gov/safety/medwatch).