The dissociative effects of PCP, also known as phencyclidine, cause patients to have disorganized thought processes, including delirium, amnesia, paranoia, and dysphoria. Therefore, obtaining a reliable history may not be possible.
The presentation of patients with PCP intoxication widely varies from inebriated and calm to agitated and, in some cases, extremely violent. An important diagnostic clue is nystagmus (lateral, horizontal, or rotatory). Many CNS depressants can produce nystagmus when taken in high doses; however, the patient is generally sedated when nystagmus is observed. In PCP exposure, the patient may have nystagmus when he or she is awake and agitated. Additional autonomic effects at low doses (< 5 mg) include hypertension, tachycardia, tachypnea with shallow breathing, salivation, flushing, and diaphoresis.
Central and peripheral nervous system effects include generalized numbness of extremities and loss of muscle coordination, and mental status can vary from stimulation and euphoria to depression and coma, which occur in a dose-related manner. At high doses (≥ 10 mg) blood pressure, heart rate and respiration rate may decrease. This is often accompanied by nausea, vomiting, blurred vision, drooling, ataxia, and dizziness.
Psychobehavioral features of PCP intoxication often mimic symptoms of schizophrenia and can include delusions, hallucinations, acute anxiety, paranoia, disorganized thinking, violence, and a sensation of distance from one's environment. Symptoms of anxiety are frequently heightened. Long-term abuse of PCP may produce memory loss, speech difficulties, depression, and weight loss. Addiction to and withdrawal from PCP can occur after chronic use and manifest as craving and compulsive PCP-seeking behavior.
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Cite this: Richard H. Sinert. Fast Five Quiz: Psilocybin and Other Hallucinogenic Drugs - Medscape - Sep 07, 2021.