Selective homomeric P2X3 and heteromeric P2X2/3 receptor antagonist (pIC50 values are 7.0 and 5.9 respectively) that exhibits no activity at P2X1, P2X2, P2X4, P2X5 and P2X7 receptors (IC50 > 10 μM). Attenuates nociceptive sensitivity in animal models of pain. Orally active and brain penetrant.