From the Guidelines
Urea is a recommended treatment for Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) due to its effectiveness in correcting hyponatremia with minimal side effects. For adults with symptomatic hyponatremia due to SIADH, oral urea can be administered at doses of 15-60 grams daily, typically starting at 15-30 grams per day divided into 2-3 doses 1. The medication can be dissolved in water or juice to improve palatability, as it has a bitter taste. Treatment duration depends on the underlying cause of SIADH, with some patients requiring long-term therapy. Urea works by inducing an osmotic diuresis, increasing free water excretion in the kidneys while sparing sodium and potassium. This mechanism helps correct hyponatremia by removing excess free water from the body.
Some key points to consider when treating SIADH with urea include:
- Monitoring blood sodium levels regularly during treatment, with sodium correction not exceeding 8-10 mEq/L in 24 hours to avoid osmotic demyelination syndrome
- Urea can be particularly useful in chronic SIADH when fluid restriction is ineffective or poorly tolerated
- Unlike fluid restriction, which is often difficult for patients to maintain, or vaptans which can be expensive and have safety concerns, urea is generally well-tolerated with minimal side effects beyond gastrointestinal discomfort 1.
In the context of SIADH, it is essential to consider the underlying cause of the condition, such as ectopic vasopressin secretion, and to manage it accordingly. In some cases, such as small cell lung cancer, successful anti-tumor therapy can lead to the reversal of SIADH 1.
From the Research
Urea and SIADH
- Urea is used as a treatment option for the syndrome of inappropriate antidiuretic hormone secretion (SIADH) [ 2 ].
- A study compared the efficacy, tolerability, and safety of two oral vaptans with those of oral urea in patients with SIADH, and found that urea has efficacy similar to that of vaptans for treatment of chronic SIADH [ 2 ].
- Urea improved natremia with the same efficacy as vaptans during the 1-year urea treatment period, with tolerance generally good for both agents [ 2 ].
Treatment Options for SIADH
- Treatment options for SIADH include fluid restriction, demeclocycline, urea, frusemide, and saline infusion, all of which have their limitations [ 3 ].
- The introduction of the vasopressin-2 receptor antagonists has allowed clinicians to specifically target the underlying pathophysiology of SIADH [ 3 ].
- Initial studies have shown good efficacy and safety profiles in the treatment of mild to moderate hyponatraemia [ 3 ].
Management of SIADH
- Patients' extensive medical history and structured physical and biochemical tests are considered the milestones marking the way of the SIADH management [ 4 ].
- Optimal management of SIADH-induced hyponatremia can result in improved outcomes and lower health costs [ 4 ].
- Long-term low-dose tolvaptan is safe and effective in SIADH treatment, with no cases of overcorrection documented and mild side effects reported [ 5(https://link.springer.com/article/10.1007/s40618-023-02131- erotisch) ].