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Desmopressin Hyponatraemia — ESENeph MCQ

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ModerateElectrolyte DisordersDesmopressin HyponatraemiaESENeph

A 52-year-old woman presents to the emergency department with serum sodium of 104 mmol/L. She is drowsy but has no seizures. She is euvolaemic with concentrated urine (osmolality 580 mOsm/kg) and urine sodium 65 mmol/L. She was started on Desmopressin 3 weeks ago for nocturia. What is the cause and treatment?

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Correct answer: E — Desmopressin-induced hyponatraemia – stop Desmopressin and cautious water restriction

Desmopressin (a synthetic ADH analogue) is used for nocturia and diabetes insipidus. When combined with normal or increased fluid intake, it causes water retention and dilutional hyponatraemia – essentially iatrogenic SIADH. This is a well-recognised adverse effect, particularly in older patients. Management involves stopping Desmopressin, fluid restriction, and cautious sodium correction (limit <10 mmol/L in 24 hours to avoid osmotic demyelination). Severe symptomatic cases may require hypertonic saline.

Reference: Spasovski et al 2014 – Hyponatraemia Guideline; BNF 2024 – Desmopressin