Tolvaptan in the treatment of SIADH-associated hyponatremia in acute lymphoblastic leukemia and lymphoblastic lymphoma: a retrospective study

Hyponatremia due to syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a recognized complication of chemotherapy in children. Fluid restriction, the conventional management strategy, is often challenging in pediatric oncology due to competing requirements for hydration and nutritional support. Evidence for the use of tolvaptan in this setting remains limited.This retrospective study evaluated the efficacy and safety of tolvaptan in chemotherapy-associated SIADH. Seventeen patients were included, with eight managed using supportive therapy (January 2021-April 2023) and nine receiving tolvaptan (May 2023-November 2025). The primary outcome was time to serum sodium normalization (≥135 mEq/L). Secondary outcomes included 24-h sodium correction, recurrence, and safety.Tolvaptan resulted in a significant increase in serum sodium at 24 h (mean increase 6.5 mEq/L, p = 0.006) and a markedly shorter median time to normalization compared with conventional management (4 vs 25 days), indicating a clinically meaningful benefit. No serious adverse events or overly rapid correction were observed. Tolvaptan may represent a safe and clinically useful option for managing SIADH in pediatric oncology, particularly when fluid restriction is not feasible.