Final answer:
The most appropriate action for a patient with a PCP overdose is to place them in a quiet room with dim lighting to help reduce sensory stimulation and calm the patient. Administering fluids or altering urine pH is not the standard initial treatment for PCP overdose.
Step-by-step explanation:
A patient admitted to the emergency department due to an overdose of phencyclidine (PCP) exhibiting psychotic behavior should be managed with actions aimed at ensuring safety and reducing stimulation. Among the options provided, the most appropriate action by the nurse would be to place the patient in a quiet room with dim lighting. This environment helps to minimize sensory stimulation, which can exacerbate psychotic symptoms, and helps to calm the patient. Administering fluids for hypotension or instructions to take deep breaths would be less specific measures in the context of PCP overdose, and altering urine pH with ammonium chloride is not a standard treatment in this scenario.
It is also noteworthy that PCP is a dissociative drug and can cause hallucinations and delusions in users. In treating patients with any kind of poisoning, including that from nerve agents or other substances, a combination of symptom management and specific antidotes might be deployed. However, in the case of a PCP overdose, creating a safe and quiet environment is a key step in initial management.