Competitive AMPA/kainate antagonist. In rat cortical membranes, displays high affinity for [3H]-AMPA (Ki = 120 nM) and [3H]-CNQX (Ki = 32 nM) binding sites and low affinity for kainate and NMDA channel-associated binding sites (IC50 values range from 2.5 to 11 μM). Inhibits currents induced by AMPA, kainate and NMDA with IC50 values of 21 nM, 27 nM, and > 1 μM respectively. Displays anxiolytic, anticonvulsant and muscle relaxant activity in vivo.