Urea beneficial in managing SIADH-induced hyponatremia

Urea appears safe and effective for treating patients with syndrome of inappropriate antidiuretic hormone secretion (SIADH)-related hyponatremia, according to the results of a meta-analysis.

Researchers searched multiple online databases for clinical trials and observational studies in which the effect of nasogastric urea administration was evaluated in terms of at least one outcome related to serum sodium concentration, symptom resolution, or adverse effects.

Pooled data from the included observational studies showed that in patients with SIADH, urea treatment resulted in a substantial increase in serum sodium (mean difference [MD], 9.08, 95 percent confidence interval [CI], 7.64–10.52; p<0.01) and urea (MD, 31.66, 95 percent CI, 16.05–47.26; p<0.01). However, there was high heterogeneity across the included studies.

In subgroup analysis defined by treatment duration, urea treatment was associated with a significant increase in the serum sodium level after 24 hours and on days 2, 5, 7, and 14, as well as after 1 year of treatment.

Notably, the rise in serum sodium levels after urea treatment was greater for patients with severe (<120 mEq/L) SIADH-induced hyponatremia (MD, 18.04, 95 percent CI, 13.68–22.39) than those with moderate (120–129 mEq/L) (MD, 7.86, 95 percent CI, 6.78–8.94) or mild (130–135 mEq/L) (MD, 8.00, 95 percent CI, 7.31–8.69) SIADH-induced hyponatremia.

The effect of urea treatment was similar to that of fluid restriction (MD, 0.81, 95 percent CI, −0.93 to 2.55; p=0.4) and vaptans (MD, −1.96, 95 percent CI, −4.59 to 0.66; p=0.1) but superior relative to no treatment (MD, 7.99, 95 percent CI, 6.25–9.72; p<0.01).

In terms of safety, urea was associated with minor adverse events, including poor palatability.

The meta-analysis was limited to observational studies due to the absence of randomized controlled trials investigating urea as a treatment for hyponatremia.