Abstract
Management of hyponatremia in patients with syndrome of inappropriate antidiuretic hormone secretion (SIADH) is challenging and cumbersome for both patients and medical staff. This is partly because traditional treatments such as 3% hypertonic saline correct hyponatremia by increasing sodium intake. By contrast, administration of tolvaptan, a vasopressin-2 receptor antagonist, corrects hyponatremia by increasing free water excretion, and has recently been reported as a rapid and efficient treatment of hyponatremia. We here report a case of severe SIADH secondary to small-cell lung cancer (SCLC) treated with tolvaptan in the acute and subacute settings without serious adverse effects. An 80-year-old man was admitted to our hospital due to disturbed consciousness and a serum sodium level (SSL) of 103 mmol/l. He was diagnosed with SCLC and severe SIADH. Consequently, we administered tolvaptan (7.5 mg, orally). With close monitoring of the SSL and urine output every 6 hr during the initial phase, the SSL increased 4-10 mmol/l/day without severe adverse effects. The SSL reached 130 mmol/l, and his clinical symptoms ameliorated on the fifth day of hospitalization. Due to his terminal-stage SCLC, the same dose of tolvaptan was continued as palliative care. The SSL remained adequate for >3 months, and no neurological deficits were observed. Administering tolvaptan may represent an effective therapeutic approach in the acute and subacute phases of SIADH and may hence contribute considerably to their quality of life.
