Management of Hyponatremia with Urea Therapy
The urea tablet dose should be increased from 15 mg to the previous higher dose due to the drop in serum sodium from 137 to 133 mmol/L, as urea is an effective treatment for hyponatremia and the current dose appears insufficient to maintain normal sodium levels. 1, 2
Assessment of Current Situation
- The patient is a 60-year-old woman whose serum sodium has decreased from 137 to 133 mmol/L after tapering urea tablets to 15 mg 1
- This drop in sodium level indicates that the current urea dose is insufficient to maintain normal sodium levels 2
- Hyponatremia (serum sodium <135 mmol/L) requires treatment to prevent complications and improve outcomes 3
Rationale for Increasing Urea Dose
- Urea is an effective treatment for hyponatremia with studies showing median serum sodium increases of 2 mEq/L per day after administration 1
- Research demonstrates that urea therapy significantly increases serum sodium levels from baseline to discharge (124.2 ± 4 vs 130.1 ± 5.1 mEq/L; P < .001) 1
- Discontinuation of urea therapy can lead to recurrence of hyponatremia, necessitating reintroduction of the medication 4
- Patients who received urea as the sole treatment for hyponatremia showed a larger increase in plasma sodium at 24 hours compared to untreated patients (2.5 mEq/L vs -0.5 mEq/L; P=0.04) 2
Recommended Approach
- Increase urea tablet dose to previous higher dose to restore sodium balance 1, 2
- Monitor serum sodium levels every 24-48 hours until stabilized 4
- Target a serum sodium level of ≥135 mmol/L 2
- Once stabilized, maintain the effective dose rather than attempting further tapering 4
Dosing Considerations
- Effective urea dosing in studies ranges from 15-30 g three to four times daily 5
- For fluid restriction-refractory hyponatremia, a starting dose of ≥30 g/day is recommended 6
- Median dose of 30 g/day has been shown to increase serum sodium by approximately 2 mEq/L per day 1
Monitoring Parameters
- Monitor serum sodium levels regularly to assess response to therapy 4
- Watch for signs of overly rapid correction (increase >8 mEq/L in 24 hours), which occurred in 8% of patients in one study 1
- Monitor for potential side effects, though urea is generally well-tolerated 2, 5
Potential Pitfalls to Avoid
- Inadequate dosing leading to persistent hyponatremia 6
- Overly rapid correction of sodium levels (>8 mmol/L in 24 hours) which could lead to osmotic demyelination syndrome 3
- Discontinuing urea therapy prematurely, which may result in recurrence of hyponatremia 4
Special Considerations
- If the patient has liver disease or malnutrition, more cautious correction rates (4-6 mmol/L per day) are recommended 3
- For patients with cirrhosis, fluid restriction to 1-1.5 L/day may be necessary if sodium drops below 125 mEq/L 3
- Urea therapy is particularly useful in patients who are unable to adhere to fluid restriction 6