Medical Pharmacology Chapter 16:  Pharmacology of Antipsychotics Drugs

Clinical Cases

• Case 3: Distinguishing primary psychosis from substance/medical causes

  • A 32‑year‑old man is brought to the ED by friends for agitation and paranoia.

    • Over the past 2 days he has been awake almost continuously, pacing, and insisting that “bugs are crawling under my skin.”

    • He admits to heavy cocaine use over the weekend and occasional amphetamine pills.

    • He appears diaphoretic and tachycardic, with pressured speech and marked psychomotor agitation. He reports seeing “shadowy figures” in the corners.

    • He has no prior psych history.

  • Questions

    • What is the most likely explanation for his psychosis at this time?

    • What clinical features in the history and exam support this over a primary psychotic disorder?

    • What elements of workup and follow‑up help you avoid missing an emerging primary psychotic illness?

  • Explained answers

    • Most likely explanation

      • The picture is consistent with substance‑induced psychotic disorder, most likely stimulant (cocaine/amphetamine)–induced psychosis.

      • There is a close temporal relationship between heavy stimulant use and acute onset of psychosis with prominent agitation and autonomic activation.

    • Features supporting substance‑induced etiology

      • Acute onset over 1–2 days, coinciding with heavy cocaine/amphetamine use.

      • Prominent autonomic signs (diaphoresis, tachycardia) and severe agitation.

      • Tactile hallucinations (“bugs crawling under skin”) and visual phenomena (“shadowy figures”) are typical of stimulant intoxication.

      • Absence of a longer prodrome or functional decline (by the history given) and no prior psychotic episodes.

    • Workup and follow‑up

      • Acute workup: full tox screen, metabolic panel, CK, ECG, and other labs to assess for medical complications (rhabdomyolysis, arrhythmia, hyperthermia).

      • Monitor the course after abstinence: if psychosis resolves fully within days of detox and does not recur without substances, that supports a purely substance‑induced episode.

      • If psychotic symptoms persist weeks beyond abstinence or reappear with minimal or no substance use, you should reassess for a primary psychotic disorder, particularly if negative symptoms or cognitive deficits become evident.

      • Thus, longitudinal observation is crucial; the case is a good illustration of why you rarely “close” the diagnostic formulation after a single acute presentation.
        

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