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Difficulty: EasyMedical History Evaluation

An ambulatory care physician conducts a same-day evaluation for a 32-year-old woman reporting a three-day history of worsening nausea, unsteady gait, and a coarse tremor in both hands. Her past medical history is significant for bipolar disorder, which has been excellently controlled on a stable dose of lithium carbonate for the past four years. She denies any recent changes to her prescribed psychiatric medications. The patient mentions she sustained a moderately painful ankle sprain while hiking four days ago. Which of the following details, if elicited during the medical history, would best explain her current clinical presentation?

  1. Routine scheduled use of over-the-counter naproxen for joint analgesiaAnswer
  2. B
    Intermittent use of over-the-counter acetaminophen for pain control
  3. C
    Increased consumption of tyramine-rich foods during the hiking trip
  4. D
    Daily application of an over-the-counter topical lidocaine patch
  5. E
    Brief episode of mild orthostatic dizziness following the injury

Answer

Routine scheduled use of over-the-counter naproxen for joint analgesia
The correct answer identifies the use of naproxen, a nonsteroidal anti-inflammatory drug (NSAID). Lithium is a renally cleared medication with a narrow therapeutic index. NSAIDs inhibit cyclooxygenase (COX), which decreases renal prostaglandin synthesis. This leads to afferent arteriolar vasoconstriction, reduced glomerular filtration rate, and increased proximal tubular reabsorption of sodium and lithium. The resulting accumulation of lithium precipitates acute toxicity, characterized by gastrointestinal symptoms (nausea, vomiting), neurologic changes (ataxia, confusion), and a coarse tremor. Eliciting a history of over-the-counter NSAID use is an essential part of the medical history evaluation in this presentation.

Step-by-Step Solution

1
Identify the clinical syndrome from the patient's presenting symptoms.
Nausea, ataxia, and a coarse tremor in a patient taking lithium indicates acute lithium toxicity.
Recognizing the toxidrome is the first step in determining its trigger.
2
Analyze the timeline and context of the presentation.
The toxicity developed over three days following a moderately painful ankle sprain.
Recent traumatic events often prompt patients to self-medicate with over-the-counter analgesics, which must be explicitly queried during the history.
3
Correlate the patient's history with known pharmacokinetics.
NSAIDs like naproxen inhibit prostaglandin synthesis, reducing renal afferent arteriolar vasodilation and significantly decreasing lithium clearance.
Understanding drug-drug interactions is critical for evaluating the history of a patient on medications with narrow therapeutic indices.

Key Concept

Evaluation of over-the-counter medication history in patients on narrow therapeutic index drugs
Estimated Time:1m 0s
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Topics

Medical History Evaluation

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