Which of the following is a characteristic of ketamine?

• A. GABA receptor agonist
• B. Causes paralysis
• C. Produces analgesia only
• D. NMDA receptor antagonist

Answer: (D)

Ketamine’s defining action is blocking NMDA receptors, which are a key part of excitatory glutamatergic signaling in the brain. This NMDA receptor antagonism produces dissociative anesthesia with analgesia and amnesia, while often preserving airway reflexes and spontaneous breathing. Because it works through NMDA blockade rather than GABAergic mechanisms, it is not a GABA receptor agonist. It also does not cause true paralysis; muscle tone is often maintained and the patient may appear dissociated rather than immobile. It provides analgesia in addition to anesthesia, rather than being analgesia-only. These features together point to NMDA receptor antagonism as the characteristic description of ketamine.