A 19-year-old college student is brought to the emergency department after ingesting an unknown substance at a party. He has dilated pupils, tachycardia, hypertension, diaphoresis, and is extremely agitated. He is seeing geometric visual hallucinations and reports the walls are 'breathing.' His temperature is 37.4°C and toxicology screen is positive only for the substance in question. Which substance is most likely responsible?
- A Phencyclidine (PCP)
- B Gamma-hydroxybutyrate (GHB)
- C Heroin
- D Lysergic acid diethylamide (LSD) ✓
Explanation
LSD (a hallucinogen) produces perceptual distortions, visual hallucinations, synesthesia, and a subjective sense of environmental animation ('breathing walls') predominantly through 5-HT2A receptor agonism in the cortex. It causes sympathomimetic signs (dilated pupils, tachycardia, hypertension) but does not typically cause vertical nystagmus or profound dissociation. PCP (an NMDA antagonist) causes nystagmus, analgesia, and violent dissociative states rather than true hallucinations. GHB causes CNS depression. Heroin causes miosis and respiratory depression, not hallucinations.
Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.