Non-competitive NMDA receptor antagonist that acts at the polyamine modulatory site. Selective for NR2B- over NR2A- and NR2C-containing receptors (IC50 values are 1, > 100 and > 100 μM respectively). Also σ1 ligand (Ki = 0.013 μM). Antagonizes neuronal voltage-gated Ca2+ channels and selectively inhibits the rapid component of the delayed rectifier K+ current (IKr). Neuroprotective.