Tolvaptan and urea in paediatric hyponatraemia

Background: The syndrome of inappropriate antidiuretic hormone (SIADH) is usually treated with fluid restriction. This can be challenging in patients with obligate fluid intake for nutrition or medication. Pharmaceutical treatment with tolvaptan and urea is available but minimal paediatric data are available. We review the efficacy and safety of tolvaptan and urea in paediatric patients diagnosed with SIADH. Methods: Retrospective review of paediatric inpatients with clinical diagnosis of SIADH. Patients were identified from pharmacy records, based on tolvaptan and urea prescriptions. Relevant information was extracted from patient electronic records. The main outcome measures included: number of days to sodium normalisation, daily change in plasma sodium concentration and maximum increase of plasma sodium concentration in 24hrs . Reported side effects were also captured. Results: Tolvaptan use led to plasma sodium normalisation in 10/13 (77%) within six days (median 2.5 days, range [1,6]) with a median change of sodium concentration of 7 mmol/L (-1,14) within the first 24 hours of treatment. Three patients experienced a change in plasma sodium >10 mmol/l/day but had no apparent side effects. Urea use led to sodium normalisation in 5/6 (83%) patients. Median number of days to normalisation with urea was 2 (1,10) with a median change of plasma sodium concentration of 2 mmol/L (-1,6) within the first 24hours. All patients tolerated tolvaptan and/or urea without unexpected side effects. Conclusions: Tolvaptan and urea appear to be safe and effective when fluid restriction is challenging in paediatric SIADH.