A 19-year-old college student is brought to the ER after ingesting two tablets at a music festival. He is agitated, violent, and has nystagmus, hypertension, and dissociative behavior. Urine drug screen is negative for opioids, cocaine, and amphetamines. Which substance is most likely responsible?
- A MDMA (Ecstasy)
- B Phencyclidine (PCP) ✓
- C LSD
- D Gamma-hydroxybutyrate (GHB)
Correct answer: B. Phencyclidine (PCP)
Explanation
Phencyclidine (PCP) causes a characteristic toxidrome of violent agitation, nystagmus (horizontal, vertical, or rotary), hypertension, and dissociative anesthesia. It is not detected on standard urine immunoassay drug screens, which is a key distinguishing feature. MDMA and amphetamines share cross-reactivity on screens, LSD rarely causes violent agitation, and GHB causes sedation rather than agitation.
Reference: Goldfrank's Toxicologic Emergencies, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.