NMDA receptor antagonist Any substance that inhibits the action of <em>N</em>-methyl-<small>D</small>-aspartate (NMDA) receptors. They tend to induce a state known as dissociative anesthesia, marked by catalepsy, amnesia, and analgesia, while side effects can include hallucinations, nightmares, and confusion. Due to their psychotomimetic effects, many NMDA receptor antagonists are used as recreational drugs. chebi_ontology NMDAR antagonist NMDAR antagonists N-methyl-D-aspartate receptor antagonists CHEBI:60643 N-methyl-D-aspartate receptor antagonist NMDA receptor antagonists CHEBI:60797 excitatory amino acid antagonist