A 22-year-old man is brought to the emergency department after attending a party. He is violently agitated, combative, and requires restraint. He appears to feel no pain during procedures, and examination reveals both horizontal and vertical nystagmus with marked tachycardia. Urine toxicology is sent. The substance most consistent with this presentation is:
- A Phencyclidine ✓
- B Methamphetamine
- C MDMA (ecstasy)
- D Synthetic cannabinoids
Correct answer: A. Phencyclidine
Explanation
Nystagmus, especially vertical nystagmus, in a combative patient with marked analgesia is the classic discriminator for phencyclidine (PCP) intoxication. Stimulants such as methamphetamine and MDMA cause agitation, mydriasis, and tachycardia but do not produce nystagmus or profound analgesia. Synthetic cannabinoids cause anxiety, psychosis, and tachycardia but also lack nystagmus. The combination of violence, analgesia, and multidirectional nystagmus points specifically to PCP.
Reference: Kaplan and Sadock's Synopsis of Psychiatry, 12th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.