The invention relates to the use of the peptide toxin APETx2 that blocks the ASIC3 cationic channels and that is derived from the Anthopleura elegantissima sea anemone, and to the use of the analogs and derivatives thereof as a drug, particularly as an analgesic pain associated with the activation of ASIC3 (Acid Sensing Ion Channel 3) channels, in particular pain occurring upon an inflammation and potentially upon any painful situation associated with tissue acidosis (ischemiae, fractures, hematoma, oedema, phlyctena, local infections, tissue lesions, ocular wounds, tumours, etc.).