Which medication is most likely responsible for hyponatremia in this patient?

Which medication is most likely responsible for hyponatremia in this patient?

• A. Furosemide
• B. Paracetamol
• C. Lisinopril
• D. Citalopram

Answer: (D)

Hyponatremia from drugs is often due to SIADH, where a medication causes inappropriate ADH release or action, leading to water retention and dilution of serum sodium. Among the options, citalopram, an SSRI, is a well-known inducer of SIADH. It can increase ADH secretion and enhance the kidney’s response to ADH, producing dilutional hyponatremia—especially in older adults and often within the first weeks of therapy. This makes it the most likely culprit in a patient with hyponatremia on these medications. Furosemide can cause hyponatremia but typically via volume depletion and electrolyte loss; paracetamol does not affect sodium balance; lisinopril rarely contributes to hyponatremia.

Hyponatremia from drugs is often due to SIADH, where a medication causes inappropriate ADH release or action, leading to water retention and dilution of serum sodium. Among the options, citalopram, an SSRI, is a well-known inducer of SIADH. It can increase ADH secretion and enhance the kidney’s response to ADH, producing dilutional hyponatremia—especially in older adults and often within the first weeks of therapy. This makes it the most likely culprit in a patient with hyponatremia on these medications. Furosemide can cause hyponatremia but typically via volume depletion and electrolyte loss; paracetamol does not affect sodium balance; lisinopril rarely contributes to hyponatremia.