What medication is used to treat hyponatremia?

Treatment of Hyponatremia Based on Etiology and Severity

The treatment of hyponatremia should be tailored to the underlying cause, severity of symptoms, and volume status, with options including fluid restriction, hypertonic saline, salt tablets, vasopressin antagonists, and fludrocortisone depending on the specific clinical scenario. 1

Initial Assessment and Classification

Hyponatremia management requires proper classification based on:

1. Volume status:

   • Hypovolemic (depleted)
   • Euvolemic (normal)
   • Hypervolemic (overloaded) 1, 2

2. Severity:

   • Mild: 126-135 mEq/L
   • Moderate: 120-125 mEq/L
   • Severe: <120 mEq/L 1

3. Symptom severity:

   • Mild: nausea, headache, weakness
   • Severe: seizures, altered mental status, coma 2

Treatment Algorithms by Volume Status

1. Hypovolemic Hyponatremia

• First-line: Isotonic (0.9%) saline infusion 1
• Monitoring: Check serum sodium every 4-6 hours during correction
• Rate of correction: 4-6 mEq/L in 24 hours, not exceeding 8 mEq/L/day 1

2. Euvolemic Hyponatremia (including SIADH)

• First-line: Fluid restriction to <1000 mL/day 1
• Second-line options:
  • Salt tablets (NaCl 100 mEq PO TID) if fluid restriction insufficient 3, 1
  • Urea (considered effective and safe) 1, 4
  • Vasopressin antagonists (tolvaptan) for persistent hyponatremia 3, 5

3. Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• First-line: Fluid restriction to 1000 mL/day 1
• Additional measures:
  • Loop diuretics (in edematous states) 1
  • Discontinuation of diuretics if they're causing hyponatremia 1
  • Vasopressin antagonists (tolvaptan) may be considered for persistent severe hyponatremia 3, 5
  • Albumin infusion for patients with cirrhosis and ascites 1

Management of Severe Symptomatic Hyponatremia

For patients with severe symptoms (seizures, altered mental status):

1. Immediate treatment: 3% hypertonic saline 3, 1

   • Initial bolus or continuous infusion
   • Target correction: 4-6 mEq/L in first 6 hours or until severe symptoms improve 3

2. Rate of correction:

   • Total correction should not exceed 8 mEq/L over 24 hours 3
   • If 6 mEq/L is corrected in first 6 hours, limit to additional 2 mEq/L in next 18 hours 3

3. Monitoring: Check serum sodium every 2-4 hours during active correction 3, 1

Special Considerations for Vasopressin Antagonists (Tolvaptan)

• Indications: Clinically significant hypervolemic and euvolemic hyponatremia (serum sodium <125 mEq/L or symptomatic hyponatremia resistant to fluid restriction) 5

• Administration:

  • Must be initiated in hospital setting with close monitoring 5
  • Starting dose: 15 mg once daily
  • May increase to 30 mg after 24 hours, maximum 60 mg daily 5
  • Maximum duration: 30 days (to minimize risk of liver injury) 5

• Contraindications:

  • Autosomal dominant polycystic kidney disease
  • Inability to sense or respond to thirst
  • Hypovolemic hyponatremia
  • Concurrent use of strong CYP3A inhibitors
  • Anuria 5

• Caution: Risk of too rapid correction (>12 mEq/L/24 hours) leading to osmotic demyelination syndrome 5

Important Caveats and Pitfalls

1. Avoid overly rapid correction of chronic hyponatremia to prevent osmotic demyelination syndrome (dysarthria, mutism, quadriparesis, seizures, coma) 3, 5, 2

2. Chronic hyponatremia should be corrected more slowly than acute hyponatremia 3

3. Patients with malnutrition, alcoholism, or advanced liver disease are at higher risk for osmotic demyelination and require slower correction rates 5

4. Fluid restriction should be avoided in the first 24 hours of tolvaptan therapy 5

5. Hypertonic saline misuse can worsen edema and ascites in hypervolemic hyponatremia 1

6. Close monitoring is essential during treatment, with frequent checks of serum sodium, fluid status, and neurological status 1

By following these evidence-based approaches and carefully monitoring correction rates, clinicians can effectively manage hyponatremia while minimizing the risk of complications.