S1RA-(hydro-chloride)

S1RA is a sigma-1 (σ1) receptor antagonist (Ki = 17 nM). It is selective for σ1 receptors over σ2 receptors (Ki = 9,300 nM), as well as a panel of 170 additional receptors at 1 µM. S1RA reduces capsaicin-induced mechanical allodynia, formalin-induced licking and biting behavior, and partial sciatic nerve ligation-induced thermal hyperalgesia in mice (ED50s = 26.3, 43.7, and 18.8 mg/kg, respectively). It also enhances fentanyl- or loperamide-induced analgesia without affecting gastrointestinal transit in mice.