Fuscoside (OPC-21268) is an orally effective, nonpeptide, vasopressin V1 receptor antagonist with an IC50 of 0.4 μM.
The concentration of Fuscoside (OPC-21268) that displaces 50% of specific AVP binding (IC50) is 0.4 μM for VI receptors and 100 μM for V2 receptors. The inhibition constant (Ki) of Fuscoside (OPC-21268) for V1 receptors (0.14 μM)[1].
Fuscoside (OPC-21268) competitively and specifically antagonizes pressor responses to AVP in vivo. Oral administration of Fuscoside (OPC-21268) (10 mg/kg) inhibits the vasoconstriction induced by exogenous AVP in a dose- and time-dependent manner and the effect lasts for more than 8 hours at 30 mg/kg[1]. Fuscoside (OPC-21268) predominantly exerts a protective effect in areas where the maximum amount of blood-brain barrier breakdown occurs, and it is effective in the treatment of cold-induced vasogenic brain edema. Fuscoside (OPC-21268) treatment at the dosages of 200 and 300 mg/kg significantly reduces brain water content in both hemispheres. Swelling of the traumatized hemispheres is also significantly reduced at 200 and 300 mg/kg dosages[2].
References:
[1]. Yamamura Y, et al. OPC-21268, an orally effective, nonpeptide vasopressin V1 receptor antagonist. Science. 1991 Apr 26;252(5005):572-4.
[2]. Bemana I, et al. Treatment of brain edema with a nonpeptide arginine vasopressin V1 receptor antagonist OPC-21268 in rats. Neurosurgery. 1999 Jan;44(1):148-54.