An orally bioavailable, competitive antagonist of the capsaicin-mediated activation of TRPV1 receptors (pKis = 7.6, 7.5, and 7.3 for human, rat, and guinea pig, respectively); induces rapid, reversible inhibition of capsaicin (IC50 = 3 nM)-, acid (pH 5.3)-, or heat (50°C; IC50 = 6 nM)-mediated activation of human TRPV1 (at -70 mV).