Which of the following describes the clinical effects commonly associated with NMDA antagonists such as PCP and ketamine?

• A. Euphoria, tachycardia, and hypotension
• B. violent behavior, dissociation, hallucinations, amnesia, nystagmus, ataxia
• C. Slurred speech and ataxia with normal mood
• D. Memory loss without motor effects

Answer: (B)

NMDA receptor blockade produces a distinct dissociative state with perceptual disturbances. The hallmark effects include dissociation from the environment, vivid or frightening hallucinations, and amnesia for the experience, often accompanied by involuntary eye movements (nystagmus) and impaired coordination (ataxia). These features together reflect the core action of PCP and ketamine as dissociative anesthetics.

Other patterns don’t fit as well: euphoria with tachycardia and hypotension isn’t the typical cluster for NMDA antagonists; slurred speech with ataxia and a normal mood suggests a more sedative or intoxication pattern not characterized by dissociation or hallucinations; memory loss without motor effects omits the prominent motor signs like nystagmus and ataxia that commonly accompany these drugs.