Background and Importance Normal blood sodium levels (BSL) is between 136-145 mEq/L. ISADH courses with hyponatremia, plasmatic hypoosmolality, high urine osmolality, and high natriuresis. Available drugs are demeclocycline and lithium, both nephrotoxic, and vasopressin receptor inhibitors, such as tolvaptan, which are effective but highly costly.

Aim and Objectives To describe the experience of use of urea as an alternative for treatment of ISADH and results monitored one year after treatment.

Material and Methods Retrospective observational study in which patients treated with urea (powder for oral solution) were analysed along two years (January 2020-December 2021) and one year after treatment. Data collection of: age, sex, quantification of BSL (at admission, during urea therapy, 60 days after drug administration and one year after treatment), initial therapy, duration of urea treatment and need of tolvaptan use.

Results Total of patients was 11. Mean age was 82 years (71-94 years). 45% were women. Average duration of treatment was 15 days (3-60 days). Initial therapy was hypertonic saline solution, water restriction and/or loop diuretics or potassium sparing agents. Only one patient did not tolerate urea. Dosage was variable: in 54% was 15 g daily, 27% 15 g bid and 18% 30 g daily.

Patients were classified according to initial hyponatremia: 27% had mild hyponatremia (130-135 mEq/L), 45% moderate (125-129 mEq/L), and 27% severe (<125 mEq/L).

-Mild hyponatremia 66% recovered BSL, while 33% remained mildly hyponatraemic.

-Moderate hyponatraemia, 60% normalised BSL and 20% worsened to severe hyponatraemia. 20% did not analised.

-Severe hyponatremia, 66% normalised BSL. 33% did not have analytical control.

45% of patients achieved BSL once treatment ended. 27% required treatment with tolvaptan 15 mg daily.

50% of patients with urea as monotherapy maintained BSL 60 days after finishing treatment and 81.8% kept normal BSL after one year of treatment. Just 9% is still in treatment.

Conclusion and Relevance Most clinical guidelines contemplate urea as an option for hyponatremia for ISADH, but it is not clear its preference respect other alternatives. Urea is shown to be a safe and moderately effective option, and also, more effective.

Conflict of Interest No conflict of interest