Ifenprodil tartrate is a typical noncompetitive NMDA receptor antagonist. Ifenprodil tartrate exerts high affinity at NR1A/NR2B receptors (IC₅₀=0.34 μM) over 400-fold than at NR1A/NR2A receptors (IC₅₀=146 μM)^[1]. Ifenprodil tartrate inhibits GIRK (Kir3), reduces inward currents through the basal GIRK activity. Ifenprodil tartrate has the potential to be a cerebral vasodilator^[2]. IC50 & Target: IC50: 0.34 μM (NR1A/NR2B receptor); 146 μM (NR1A/NR2A receptor)^[1] In Vitro: G protein-activated inwardly rectifying K+ channels (GIRK)^[1].