How to treat hyponatremia with oral medications?

Oral Medications for Treating Hyponatremia

For mild to moderate hyponatremia, oral sodium chloride tablets (100 mEq three times daily) combined with fluid restriction to 1 L/day are the primary oral treatment options, particularly for SIADH. 1

Treatment Algorithm Based on Volume Status and Severity

Euvolemic Hyponatremia (SIADH)

Fluid restriction to 1 L/day is the cornerstone of treatment for SIADH. 1 If fluid restriction alone fails to improve sodium levels after 24-48 hours, add oral sodium chloride 100 mEq three times daily. 1

For persistent hyponatremia despite these measures:

• Tolvaptan (vasopressin receptor antagonist) starting at 15 mg once daily, titrating to 30-60 mg as needed 1, 2
• Demeclocycline as an alternative pharmacological option 1
• Urea (40 g in divided doses) can be effective, though palatability is poor 3
• Lithium (less commonly used due to side effects) 1

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

Fluid restriction to 1-1.5 L/day is first-line treatment when serum sodium <125 mmol/L. 1 Temporarily discontinue diuretics if sodium drops below 125 mmol/L. 1

For cirrhotic patients specifically:

• Albumin infusion should be tried before considering vaptans 1
• Avoid hypertonic saline unless life-threatening symptoms are present, as it worsens ascites and edema 1

Tolvaptan may be considered for persistent severe hypervolemic hyponatremia despite fluid restriction and maximization of guideline-directed medical therapy, but use with extreme caution in cirrhosis due to higher risk of gastrointestinal bleeding (10% vs 2% placebo). 1, 2

Hypovolemic Hyponatremia

Oral sodium chloride tablets are NOT appropriate for hypovolemic hyponatremia. 1 These patients require volume repletion with isotonic saline (0.9% NaCl) intravenously, not oral medications. 1 Once euvolemic, oral sodium supplementation may be considered if needed.

Critical Correction Rate Guidelines

Never exceed 8 mmol/L correction in 24 hours to prevent osmotic demyelination syndrome. 1 For high-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy), limit correction to 4-6 mmol/L per day. 1

Monitor serum sodium:

• Every 2 hours during initial correction for severe symptoms 1
• Every 4 hours after resolution of severe symptoms 1
• Daily once stable 1

Tolvaptan Dosing and Monitoring

Start tolvaptan at 15 mg once daily, avoiding fluid restriction during the first 24 hours to prevent overly rapid correction. 2 Titrate at 24-hour intervals to 30 mg, then 60 mg once daily until normonatremia (>135 mEq/L) is reached or maximum dose achieved. 2

Contraindications and cautions for tolvaptan:

• Avoid in patients with cirrhosis due to increased bleeding risk 1
• Use with extreme caution in heart failure with volume overload 1
• Monitor for overly rapid correction (>8 mmol/L/24 hours) 1
• Watch for side effects: thirst, dry mouth, increased urination 1

Common Pitfalls to Avoid

Do NOT use oral sodium tablets in:

• Severe renal failure (GFR <15) - kidneys cannot handle sodium load 1
• Hypervolemic states - worsens fluid retention 1
• Severe symptomatic hyponatremia - requires IV hypertonic saline 1

Do NOT use fluid restriction in:

• Cerebral salt wasting - worsens outcomes 1
• Subarachnoid hemorrhage patients at risk of vasospasm 1

Avoid overly rapid correction exceeding 8 mmol/L in 24 hours, which can cause osmotic demyelination syndrome manifesting as dysarthria, dysphagia, oculomotor dysfunction, or quadriparesis 2-7 days after rapid correction. 1

Special Population Considerations

For neurosurgical patients, distinguish between SIADH and cerebral salt wasting (CSW) - treatment approaches differ fundamentally. 1 CSW requires volume and sodium replacement with fludrocortisone, NOT fluid restriction. 1

For patients on diuretics with sodium 126-135 mmol/L and normal creatinine, continue diuretic therapy but monitor electrolytes closely without water restriction. 1 Stop diuretics if sodium ≤120 mmol/L. 1