For a patient presenting with paranoia and hallucinations, which substance should be ruled out first?

When evaluating a patient who presents with paranoia and hallucinations, it is crucial to rule out substances that are known to induce such psychotic symptoms. PCP (phencyclidine) is a dissociative anesthetic that is well known for its capacity to cause severe hallucinations, agitation, and paranoia. PCP can lead to profound alterations in perception, mood, and thought processing, often resulting in symptoms that mimick psychotic disorders.

Given the acute and intense nature of PCP intoxication, it is essential to rule out this substance first when observing a patient with psychotic features. The rapid onset and duration of effects associated with PCP make it a prime candidate for immediate consideration in cases of altered mental states, particularly when paranoia and hallucinations are evident.

In contrast, while cannabis can cause mild alterations in perception and anxiety, it does not typically lead to the intense symptoms seen with PCP. Alcohol also has the potential to produce psychotic symptoms, particularly during withdrawal, but PCP's specific effects make it a higher priority to rule out initially. Lastly, while certain antidepressants can lead to side effects associated with mood disturbances, they are less commonly associated with acute paranoia and hallucinations when contrasted with PCP. Thus, ruling out PCP early in the diagnostic process is