Which genitourinary medication is inappropriate for nocturia due to hyponatremia risk?

• A. Tolterodine
• B. Oxybutynin
• C. Finasteride
• D. Desmopressin

Answer: (D)

Desmopressin is inappropriate for nocturia in older adults because it can cause hyponatremia. It works by increasing water reabsorption in the kidneys, which reduces urine production at night, but this water retention can dilute serum sodium. In older individuals, even small increases in water retention or fluid intake can lead to dangerous hyponatremia, with symptoms ranging from confusion to seizures. Because of this risk, desmopressin is avoided in many older patients under Beers criteria.

The other options do not carry the same hyponatremia risk. Tolterodine and oxybutynin are anticholinergic bladder meds that mainly raise concerns for cognitive impairment and delirium in older adults, not hyponatremia. Finasteride is a 5-alpha reductase inhibitor for BPH and does not affect sodium or water balance.