[Oral urea as a safety strategy in complex syndrome of inappropriate antidiuretic hormone secretion - Challenges posed by polypharmacy and institutionalization].

Introduction: syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a common cause of euvolemic hyponatremia in older adults. Case report: we report the case of a 72-year-old woman with chronic SIADH, probably secondary to sertraline, in the setting of polyp harmacy and chronic liver disease. Initially, serum sodium normalized with fluid restriction guided by the Furst formula under caregiver supervision. Following the death of her primary caregiver and admission to a long-term care facility, an increase in sertraline dosage and the inability to maintain fluid restriction led to recurrent hyponatremia (serum sodium 126 mEq/l). Tolvaptan was avoided because of the risk of interaction with diltiazem (CYP3A4 inhibitor) and underlying liver disease. Oral urea was initiated and titrated to 30 g/day, achieving gradual and sustained normalization of serum sodium (134-135 mEq/l) without adverse effects or changes to her psychotropic treatment. Six months later, the patient remains clinically stable on 15 g/day of oral urea with progressive sertraline dose reduction. Discussion: this case highlights oral urea as a safe, effective, and cost-effective therapeutic option for SIADH when fluid restriction is not feasible and vaptans are unsuitable, particularly in frail older adults with polypharmacy and complex social circumstances.