American Board of Psychiatry and Neurology (ABPN) Practice Exam

Which substance is known to cause nystagmus during intoxication?

1. A. Heroin

2. B. Lysergic acid diethylamide (LSD)

3. C. Methadone

4. D. Phencyclidine

The correct answer is: D. Phencyclidine

Phencyclidine, commonly known as PCP, is known to cause nystagmus during intoxication. Nystagmus refers to the involuntary, rapid movement of the eyes and can be a hallmark sign of certain substance use. PCP is a dissociative anesthetic that affects multiple neurotransmitter systems, particularly glutamate and dopamine. Its intoxication can lead to various neurological and psychological effects, among which eye movement abnormalities like nystagmus are notable. In contrast, the other substances listed typically do not produce nystagmus as a prominent effect. For instance, heroin and methadone, both opioids, are associated with sedation and respiratory depression but do not typically lead to the eye movement disorder observed with PCP. LSD, a hallucinogen, can induce a range of perceptual changes and visual distortions, but nystagmus is not a characteristic effect of its intoxication. Therefore, PCP stands out as the substance predominantly known for causing nystagmus during intoxication.