[Management of syndrome of inappropriate antidiuretic hormone secretion in outpatients]

Introduction: the syndrome of inappropriate antidiuretic hormone secretion (SIADH) is the most frequent cause of hyponatremia in the outpatient setting, presenting significant diagnostic and therapeutic challenges due to the difficulty of performing laboratory monitoring and poor patient compliance with fluid restriction. Case report: we report the case of an institutionalized and polymedicated 59-year-old male, with a history of congenital epilepsy, who developed moderate euvolemic hyponatremia ([Na+] 124 mEq/l) secondary to oxcarbazepine therapy. Given the risk of a progressive decline in serum sodium, treatment with oral urea (30 g/day) was initiated, achieving a controlled and progressive increase in natremia to safe limits (133 mEq/l), even before the withdrawal of the culprit drug. Following the subsequent discontinuation of oxcarbazepine by neurology, natremia fully normalized ([Na+] 138 mEq/l), allowing a successful withdrawal of urea. Discussion: oral urea stands out as the only fully effective, safe, and well-tolerated medium- and long-term therapeutic strategy available for managing outpatient SIADH.