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Lithium toxicity — USMLE Step 3 MCQ

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HardPsychiatry (outpatient management)Lithium toxicityUSMLE Step 3

A patient with posttraumatic stress disorder has remained well on paroxetine 40 mg daily and now elects to discontinue treatment. She has no urgent reason to stop and wants the taper regimen used in the GAD and PTSD clinical trials described by the current FDA label. Which schedule matches that regimen?

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Reveal the answer and explanation

Correct answer: E — Use 30 mg daily for one week, then 20 mg daily for one week before stopping

The best answer is “Use 30 mg daily for one week, then 20 mg daily for one week before stopping”. The label recommends gradual dose reduction rather than abrupt cessation. In the GAD and PTSD trials, the daily dose was decreased by 10 mg at weekly intervals; once 20 mg daily was reached, that dose was continued for one week before treatment stopped. Starting from 40 mg daily therefore means 30 mg daily for one week, then 20 mg daily for one week, then discontinuation. Extending through 10 mg, skipping the 30-mg step, alternate-day dosing, and a fluoxetine substitution do not reproduce the labeled trial regimen.

Reference: DailyMed FDA Label: Paroxetine Tablets—Discontinuation Syndrome: https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=bc0efd3b-c6b9-4ed0-b517-6e57e4700b7b&version=33