Zonampanel (YM 872) is a selective antagonist of the glutamate receptor subtype, α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor. In Vitro: Zonampanel inhibits the human MRP4-mediated transport of [³H]oestradiol 17-D-glucuronide in a concentration-dependent manner. In contrast, Zonampanel (up to 1000 mM) does not inhibit the human MRP2- or BCRP-mediated transport of [³H]oestradiol 17-D-glucuronide or [³H]methotrexate^[1]. Zonampanel inhibits the uptake of typical substrates by Oat1, Oat2, and Oat3 with inhibition constant (K_i) values of 7.02 to 10.4 μM. A time- and saturable concentration-dependent increase in [¹⁴C]Zonampanel uptake is observed in these cells [K_m values: 13.4 to 53.6 μM]^[2]. In Vivo: In in vivo experiments, probenecid and cimetidine decrease intrinsic clearance for both the renal secretion and biliary excretion of Zonampanel^[2].