Dermorphin is a mu-opioid peptide found in the skin of a South American frog.[1] In animal tests it was hundreds to thousands of times more potent than morphine when injected into the brain.[2] Small Italian studies in the 1980s tested it for pain after surgery,[4][5] but it was never developed into an approved medicine. Today it is best known as “frog juice,” the drug at the center of the 2012 racehorse doping cases.[13] It carries the core risks of any strong opioid, including slowed breathing and dependence.
What is dermorphin?
Dermorphin is a chain of seven amino acids. Vittorio Erspamer’s research group isolated it from the skin of Phyllomedusa sauvagei and published its sequence in 1981.[1] One of its building blocks is a “right-handed” D-alanine, which was a surprise: animals almost always build peptides from “left-handed” amino acids.[1] That unusual piece is essential to its activity.[2]
It is a selective agonist of the mu-opioid receptor, the receptor that morphine, oxycodone and fentanyl act on.[3] Chemists have since made dozens of related peptides, some even stronger than the original.[3][19]
Dermorphin vs morphine
How much stronger dermorphin is depends on how it is given and measured:
| Test | Dermorphin compared with morphine |
|---|---|
| Guinea-pig gut tissue | About 39 times more potent[2] |
| Mouse vas deferens tissue | About 40 times more potent[2] |
| Injected into rats’ brains (pain tests) | 752 to 2,170 times more potent[2] |
| News description from the horse-doping case | About 30 times more potent[13] |
When given under the skin, dermorphin was much less active than when injected into the brain, because only a limited amount crosses the blood-brain barrier.[5][19] In early rat studies, dermorphin caused tolerance and withdrawal like morphine did, though to a lesser degree.[2][8]
What the research shows in humans
Human research on dermorphin is small and old, and almost all of it is from the 1980s:
- Pain after surgery: In a randomized double-blind trial of 150 patients after elective surgery, a single 20 microgram dose injected into the spinal fluid relieved pain for about 43 hours. That was longer than 500 micrograms of spinal morphine (about 34 hours) or routine pentazocine injections (about 11 hours).[4]
- Earlier open studies: Preliminary open studies, with an unspecified number of patients, came before the 1985 trial. About half of patients had nausea or vomiting.[5]
- Pain reflex: An IV infusion raised the pain-reflex threshold in healthy volunteers and in a person with a complete spinal cord injury, suggesting it works largely at the spinal cord.[6]
- Hormones: IV dermorphin raised prolactin in 11 volunteers, an effect blocked by naloxone.[7]
A 2018 review argued that dermorphin was abandoned without a clear reason and called for new trials of spinal use in post-surgery and end-of-life pain.[5] ClinicalTrials.gov lists no trials of dermorphin.[21]
Dosage studied
There is no approved or recommended dose of dermorphin. The only doses reported in published human studies were given by doctors in controlled settings:
- 20 micrograms, as a single injection into the spinal fluid after surgery.[4]
- IV infusion, in a pain-reflex experiment in volunteers.[6]
- IV infusion over 30 minutes, in a hormone study.[7]
These were single doses given by clinicians in research settings. They are not a guide for anyone using dermorphin on their own.
Dermorphin side effects and risks
- Slowed breathing: In anesthetized rats, an IV dose caused breathing to stop briefly (apnea), followed by slower breathing.[9] In awake rats, high doses of a related dermorphin peptide reduced breathing and blocked the normal response to carbon dioxide.[10] Slowed breathing is the main cause of death in opioid overdose.[11]
- Dependence and withdrawal: Rats given steady dermorphin infusions into the brain developed tolerance within 48 hours and showed morphine-like withdrawal when given naloxone.[8]
- Nausea and vomiting: About half of patients in early open studies of spinal dermorphin had nausea or vomiting.[5]
- Other effects in the surgery trial: Urinary retention affected 26% on dermorphin and 30% on spinal morphine versus 18% on pentazocine, and nausea or vomiting 22% and 18% versus 14%.[5]
- Excitement and fast heart rate: In horses, IV dermorphin caused excitement and a faster heart rate for a few minutes.[12]
Some animal studies found less tolerance or breathing suppression with certain dermorphin peptides than with morphine.[3][10] These findings have not been tested in people, and the 1980s human studies used carefully measured doses given by clinicians.
Dermorphin in horse racing
Synthetic dermorphin turned up in racehorse drug tests in 2012:
- New Mexico: Independent lab tests confirmed that nine horses had been given dermorphin, and the trainers’ cases were sent to the state attorney general.[15]
- Louisiana: The Louisiana State Racing Commission sanctioned nine trainers after 11 horses tested positive.[13]
- Breed registry: The American Quarter Horse Association suspended 11 trainers already penalized in Louisiana and New Mexico for Class I drug positives, with suspensions of 3 to 21 years.[16]
In 2017 a Louisiana veterinarian and a Nebraska pharmacy were indicted for supplying dermorphin labeled as “D-Peptide.”[13] The veterinarian was later sentenced to 15 months in prison, and the pharmacy received five years of corporate probation and a $200,000 fine.[14] In horses, dermorphin stays detectable in urine for 48 to 72 hours,[12] and labs now screen for 17 dermorphin peptides at once.[19]
Is dermorphin legal?
- FDA: Not approved for human or animal use.[14] It does not appear on FDA’s May 2026 list of substances nominated for 503A compounding.[20]
- DEA: Not on the DEA’s August 2026 alphabetical list of controlled substances.[17] Selling it as a drug can still bring federal charges, as the misbranding convictions in the Louisiana case show.[14]
- Horse racing: The Louisiana State Racing Commission sanctioned nine trainers whose horses tested positive, and New Mexico referred its cases to the state attorney general.[13][15]
- Sport: Dermorphin is not named on WADA’s 2026 Prohibited List. The S0 category bans at all times any substance not covered elsewhere that has no current approval for human therapeutic use.[18]
Dermorphin vs ARA-290 and other pain peptides
Dermorphin relieves pain the same way morphine does, by switching on opioid receptors, and it shares their risks. ARA-290 works differently: it was designed to calm nerve inflammation and support repair, and has been tested in small phase 2 trials for nerve pain. Healing peptides such as BPC-157, TB-500 and KPV are not opioids and have little human data.
What users report
We found no trustworthy, non-vendor reports of human use of dermorphin outside the 1980s studies. Its documented misuse is in horse racing.[13]
