Review Question - QID 108717

The most likely diagnosis in this patient is phencyclidine (PCP) abuse. PCP is an NMDA receptor antagonist.

PCP, also known as “wet” or “angel dust,” is a recreational stimulant whose mechanism of action is to antagonize the NMDA receptor. Common effects of PCP intoxication include agitation, aggression, hallucinations, tachycardia, psychosis, delirium, and seizures. One important complication of PCP intoxication is trauma secondary to the patient’s violent behavior. Vertical nystagmus is highly specific for PCP intoxication.

Incorrect Answers:
Answer 1: Caffeine is a naturally-occurring stimulant that functions as an adenosine antagonist, which subsequently leads to decreased GABA activity and increased wakefulness. Caffeine intoxication presents with restlessness, insomnia, diuresis, and rarely cardiac arrhythmias.

Answer 2: Cocaine and amphetamines are two classes of stimulants that both inhibit reuptake of key biogenic amines (dopamine, serotonin, and norepinephrine). Amphetamines also stimulate biogenic amine release at the presynaptic terminal.

Answer 3: Opioids are depressants that act as mu receptor agonists. Opioid intoxication typically presents with somnolence, respiratory depression, pupillary constriction, and constipation.

Answer 4: Barbiturates and benzodiazepines are two classes of depressants that both act as GABA channel agonists. Barbiturates prolong the duration of GABA channel opening while benzodiazepines increase the frequency of GABA channel opening. Intoxication with either substance will present with stupor, somnolence, and respiratory depression.

Bullet Summary:
PCP is a stimulant that acts as an NMDA receptor antagonist. PCP intoxication presents with agitation, violence, psychosis, tachycardia, and vertical nystagmus.