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SIADH — USMLE Step 3 MCQ

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HardInternal Medicine (Chronic Management)SIADHUSMLE Step 3

A euvolemic patient with SIADH has sodium 124 mEq/L despite fluid restriction but has no seizure, severe confusion or other need for urgent correction. Tolvaptan is selected. Which initiation plan is appropriate?

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Correct answer: A — Start tolvaptan in hospital without initial fluid restriction and with frequent sodium monitoring

The best answer is “Start tolvaptan in hospital without initial fluid restriction and with frequent sodium monitoring”. Tolvaptan can correct sodium too rapidly, so initiation and reinitiation require hospitalization and monitoring. Fluid restriction is generally avoided during the first 24 hours, and the drug is not a substitute for hypertonic saline when urgent correction is required.

Reference: FDA Prescribing Information: SAMSCA: https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=5526617c-c7b9-4556-886d-729bbabbc566