 NMDA receptor antagonists induce a state called dissociative anesthesia, marked by catalepsy, amnesia, and analgesia.Ketamine is a favored anesthetic for emergency patients with unknown medical history and in the treatment of burn victims because it depresses breathing and circulation less than other anesthetics.Dextrorphan, a metabolite of dextromethorphan (one of the most commonly used cough suppressants in the world), is known to be an NMDA receptor antagonist.