What is the daily oral dose of sodium chloride for treating chronic hyponatremia?

Oral Sodium Chloride Dosing for Chronic Hyponatremia

For chronic hyponatremia, oral sodium chloride supplementation can be given at a dose of 100 mEq (approximately 6 grams) three times daily, typically as an adjunct to fluid restriction when first-line therapy fails. 1

Treatment Algorithm Based on Severity and Symptoms

Mild to Moderate Chronic Hyponatremia (125-135 mmol/L)

First-line therapy should be fluid restriction to 1 L/day, particularly for euvolemic hyponatremia (SIADH). 1 If the patient fails to respond to fluid restriction alone after 24-48 hours, add oral sodium chloride supplementation. 1

• Dosing: Sodium chloride 100 mEq orally three times daily (total 300 mEq/day or approximately 18 grams/day). 1
• This equates to roughly 4 mL of 23.4% sodium chloride oral solution (936 mg or 16 mEq) taken approximately 18-19 times daily, though the practical approach uses salt tablets. 2
• Monitor serum sodium every 4 hours initially, then daily once stable. 1

Severe Chronic Hyponatremia (<120-125 mmol/L)

For asymptomatic or mildly symptomatic severe chronic hyponatremia, combine fluid restriction (1-1.5 L/day) with oral sodium supplementation. 1 However, if the patient develops severe symptoms (seizures, altered mental status, coma), this becomes a medical emergency requiring intravenous 3% hypertonic saline, not oral therapy. 1, 3

Critical Correction Rate Guidelines

The maximum correction rate must not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1, 3 This is the single most important safety consideration.

• For average-risk patients: aim for 4-8 mmol/L per day. 1
• For high-risk patients (advanced liver disease, alcoholism, malnutrition, severe hyponatremia), limit correction to 4-6 mmol/L per day. 1, 4
• Chronic hyponatremia should not be corrected rapidly (>1 mmol/L/hour). 1

Volume Status Considerations

The approach differs dramatically based on volume status:

Euvolemic Hyponatremia (SIADH)

• Fluid restriction to 1 L/day is the cornerstone of treatment. 1
• Add oral sodium chloride 100 mEq three times daily if no response to fluid restriction. 1
• Alternative second-line options include urea (40 grams in divided doses) or vaptans, though oral sodium chloride is simpler and safer. 1, 5

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• Fluid restriction to 1-1.5 L/day for sodium <125 mmol/L is primary therapy. 1, 4
• Oral sodium chloride supplementation is generally NOT recommended in hypervolemic states, as it may worsen fluid overload. 1
• In cirrhotic patients, sodium restriction (not supplementation) is more important, as fluid passively follows sodium. 1, 4
• Consider albumin infusion in cirrhotic patients instead of sodium supplementation. 1, 4

Hypovolemic Hyponatremia

• Discontinue diuretics and provide volume repletion with isotonic saline (0.9% NaCl), not oral sodium tablets. 1
• Oral sodium supplementation is insufficient for true volume depletion. 1

Practical Dosing Calculation

To calculate sodium deficit: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg). 1

For example, a 70 kg patient needing a 6 mEq/L increase over 24 hours:

• Sodium deficit = 6 × (0.5 × 70) = 210 mEq over 24 hours
• This could be provided as 70 mEq three times daily (approximately every 8 hours). 1

Common Pitfalls to Avoid

• Never use home-prepared salt solutions due to potential formulation errors. 1 Use pharmaceutical-grade sodium chloride tablets or oral solution. 2
• Overly rapid correction exceeding 8 mmol/L in 24 hours can cause osmotic demyelination syndrome, a devastating and potentially fatal complication. 1, 3
• Do not use oral sodium supplementation in hypervolemic hyponatremia without life-threatening symptoms, as it worsens edema and ascites. 1
• Inadequate monitoring during active correction is dangerous. 1 Check sodium levels every 4 hours initially when using oral supplementation. 1
• Failing to recognize the underlying cause leads to treatment failure. 1 Distinguish between SIADH, cerebral salt wasting, and volume status-related causes. 1

Special Population Considerations

Alcoholism and Cirrhosis

Patients with advanced liver disease require even more cautious correction (4-6 mmol/L per day) due to higher risk of osmotic demyelination. 1, 4 These patients are at increased risk of complications including spontaneous bacterial peritonitis, hepatorenal syndrome, and hepatic encephalopathy when hyponatremic. 4

Neurosurgical Patients

Distinguish between SIADH and cerebral salt wasting (CSW), as treatment approaches differ fundamentally. 1 CSW requires volume and sodium replacement, not fluid restriction, while SIADH requires the opposite. 1

Monitoring Requirements

• Check serum sodium every 4 hours initially when actively treating with oral sodium supplementation. 1
• Once stable, transition to daily monitoring. 1
• If overcorrection occurs (>8 mmol/L in 24 hours), immediately administer free water or desmopressin to relower sodium levels. 1
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction. 1