Lockett J, et al. - In this study involving patients admitted to a tertiary hospital (2016-2017), researchers determined the safety and efficacy of urea for the treatment of fluid-restriction refractory hyponatremia. The primary endpoint consisted of a proportion of patients who achieved serum sodium ≥ 130mmol/L at 72 hours. Urea was used on 78 occasions in 69 patients (median age: 67 years; 41% female). Seventy (89.7%) had hyponatremia due to SIADH; CNS pathology (64.3%) was the most common cause. They observed that the median nadir serum sodium was 122 mmol/L and fluid restriction was first-line treatment in 65.4%. It was noted that urea was used first line in 21.8% and second line in 78.2%. Fifty treatment episodes (64.1%) resulted in 72 hours of serum sodium ≥ 130mmol/L. The mean sodium change at 72 hours was greater than with the preceding treatments in 56 patients who received other prior treatment. No patients developed hypernatremia, over-correction, or died. Overall, they concluded that urea is safe and effective in fluid-restriction refractory hyponatremia. Urea with an initial dose of ≥ 30 g/day was recommended in patients with SIADH and moderate to profound hyponatremia who are unable to undergo fluid restrictions.