What is the role of urea powder in treating hyponatremia?

Urea Powder in the Treatment of Hyponatremia

Urea powder is an effective and safe treatment option for hyponatremia, particularly in cases of SIADH and fluid restriction-refractory hyponatremia, with a recommended starting dose of 30 g/day. 1

Mechanism and Efficacy

Urea works as an osmotic diuretic that increases urinary water excretion without affecting sodium levels. It offers several advantages:

• Effectively increases serum sodium by approximately 2 mEq/L per day at a median dose of 30 g/day 2
• Does not increase ascites or edema, unlike hypertonic saline, making it suitable for certain patient populations 1
• Shows significant improvement in serum sodium levels between baseline and discharge (124.2 ± 4 vs 130.1 ± 5.1 mEq/L; P < .001) 2
• More effective than fluid restriction alone for treating hyponatremia 1
• Particularly useful in SIADH-related hyponatremia, with 64.1% of patients achieving serum sodium ≥130 mmol/L at 72 hours 3

Administration Guidelines

• Dosing: Start with 30 g/day, with possibility to adjust based on response 1
• Administration: Dissolve in water or flavored beverage to improve palatability 1
• Monitoring: Check serum sodium every 4-6 hours initially to avoid overcorrection 1
• Target correction rate: 4-6 mEq/L per day, not exceeding 8 mEq/L in 24 hours 1

Advantages Compared to Other Treatments

• Safety profile: No reported cases of osmotic demyelination syndrome in studies 1
• Cost-effectiveness: More affordable than vaptans (tolvaptan) 1
• Liver safety: Lower risk of liver injury compared to vaptans 1
• Long-term use: Suitable for chronic management of hyponatremia 4

Patient Selection

Urea is particularly beneficial for:

1. Patients with SIADH who have failed fluid restriction (64.1% success rate) 3
2. Euvolemic hyponatremia in ICU settings 5
3. Chronic hyponatremia requiring long-term management 4
4. Patients with moderate to profound hyponatremia (starting at serum sodium <130 mEq/L) 3

Potential Limitations and Side Effects

• Palatability: Poor taste is the most common side effect, reported in approximately 22.7% of patients 3
• Gastric intolerance: May cause nausea or gastrointestinal discomfort 6
• Overcorrection risk: Occurs in approximately 8% of patients, requiring careful monitoring 2
• Discontinuation: About 53% of patients may discontinue treatment, with 20% due to intolerance 2

Practical Tips for Administration

• Use flavored beverages to mask the taste
• Consider administration through gastric tube in ICU patients 5
• For severe hyponatremia (≤115 mEq/L), combine with isotonic saline initially 5
• Resume urea if hyponatremia recurs after discontinuation (occurs in approximately 12% of cases) 2

Monitoring Parameters

• Serum sodium levels every 4-6 hours during initial correction
• Blood urea nitrogen (BUN) levels, which typically increase from baseline (18.4 ± 13.1 to 41.1 ± 26.6 mg/dL) 2
• Neurological status for improvement of symptoms
• Signs of overcorrection (>8 mEq/L in 24 hours)

Cautions

• Avoid in patients with severe renal impairment
• Monitor closely in patients at risk for osmotic demyelination syndrome
• Be prepared to pause treatment if correction exceeds 8 mEq/L in 24 hours
• Consider desmopressin administration if overcorrection occurs 1