Opiorphin
Opioid Modulation / AnalgesiaAlso known as: QRFSR
Endogenous Opioid ModulatorsResearch phase: PreclinicalRegulatory: Not approved. Research peptide only.
Mechanism
Opiorphin is a natural pain-relieving peptide found in human saliva. Rather than activating opioid receptors directly, it boosts the body's own enkephalins by blocking the enzymes that break them down.
Technical detail
Opiorphin (Gln-Arg-Phe-Ser-Arg) is a pentapeptide secreted in human saliva that inhibits both neutral endopeptidase (NEP) and aminopeptidase N (APN), the two key enkephalin-degrading enzymes. This dual inhibition potentiates endogenous enkephalin signaling at mu- and delta-opioid receptors, producing analgesia comparable to morphine in rat models (1 mg/kg equianalgesic).