What is the dosage and administration of sodium chloride (NaCl) tablets for treating hyponatremia?

Sodium Chloride Tablets for Hyponatremia

Dosage and Administration

Oral sodium chloride tablets are dosed at 100 mEq (approximately 6 grams) three times daily as adjunctive therapy for mild to moderate hyponatremia due to SIADH when fluid restriction alone is insufficient. 1

Specific Dosing Protocols

Standard Dosing:

• 100 mEq orally three times daily (total 300 mEq/day or approximately 18 grams/day) for patients with SIADH who fail fluid restriction 1
• This dosing is used in conjunction with fluid restriction of 1 L/day 1

Hourly Dosing for Severe Cases:

• For severe symptomatic hyponatremia requiring rapid correction, hourly oral NaCl tablets can be calculated to deliver the equivalent of 0.5 mL/kg/hour of 3% NaCl 2
• This approach requires careful monitoring of serum sodium every 2 hours 1

Pediatric Dosing:

• Infants with polyuric salt-wasting CKD: 1-5 mmol Na/kg body weight/day, adjusted according to blood biochemistry 3
• Average effective dose in infants: 3.2 ± 1.04 mmol/kg/day 3

Indications and Patient Selection

Primary Indication:

• Euvolemic hyponatremia (SIADH) with serum sodium <130 mmol/L that fails to respond to fluid restriction alone 1
• Mild to moderate asymptomatic hyponatremia where adequate solute intake is needed 4

Appropriate Clinical Scenarios:

• Patients unable to tolerate or comply with strict fluid restriction 5
• Elderly patients with refractory SIAD where vaptan therapy poses risks 5
• Outpatient management where IV hypertonic saline is not feasible 2

Critical Contraindications

Absolute Contraindications:

• Hypervolemic hyponatremia (heart failure, cirrhosis) - salt tablets will worsen fluid overload and edema 1
• Severe renal failure (GFR <10 mL/min) - inability to excrete sodium load 1
• Severe symptomatic hyponatremia with altered mental status, seizures, or coma - requires immediate IV 3% hypertonic saline 1

Relative Contraindications:

• Hypertension requiring sodium restriction 3
• Volume overload states 1
• Patients at risk for rapid overcorrection 1

Monitoring Requirements

Initial Phase:

• Check serum sodium every 4 hours initially when starting therapy 1
• Once stable, transition to daily monitoring 1

Target Correction Rates:

• Maximum 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1
• High-risk patients (cirrhosis, alcoholism, malnutrition): 4-6 mmol/L per day 1

Additional Monitoring:

• Daily weights to assess fluid balance 1
• Blood pressure monitoring for hypertension 3
• Serum potassium and chloride levels 1

Efficacy and Evidence

Clinical Effectiveness:

• Oral NaCl tablets combined with fluid restriction safely increased serum sodium in elderly patients with refractory SIAD, reducing hospital length of stay 5
• Hourly oral NaCl provides graded and predictable increases in serum sodium concentration comparable to IV 3% NaCl 2

Comparative Effectiveness:

• A randomized controlled trial found that furosemide plus NaCl supplementation (3 g/day) combined with fluid restriction did not show additional benefit over fluid restriction alone in SIAD 6
• However, this lower dose (3 g/day = ~50 mEq/day) is substantially less than the recommended 300 mEq/day for refractory cases 1, 6

Important Safety Considerations

Home Preparation Warning:

• Home preparation of sodium chloride supplements using table salt is NOT recommended due to potential formulation errors that could result in hypo- or hypernatremia 3
• Use pharmaceutical-grade sodium chloride tablets only 3

Risk of Overcorrection:

• If sodium increases >8 mmol/L in 24 hours, immediately discontinue NaCl tablets and administer D5W or desmopressin to relower sodium 1
• Monitor for osmotic demyelination syndrome symptoms: dysarthria, dysphagia, oculomotor dysfunction, quadriparesis (typically 2-7 days post-correction) 1

Volume Status Assessment:

• Confirm euvolemic status before initiating salt tablets 1
• Urine sodium >20-40 mmol/L with urine osmolality >300 mOsm/kg supports SIADH diagnosis 1
• Distinguish from cerebral salt wasting (which requires volume replacement, not salt tablets alone) 1

Treatment Algorithm

Step 1: Confirm SIADH

• Euvolemic on exam (no edema, orthostasis, or volume overload) 1
• Serum sodium <130 mmol/L 1
• Urine osmolality >100 mOsm/kg with urine sodium >20 mmol/L 1

Step 2: Initial Therapy

• Fluid restriction to 1 L/day for 3-5 days 1
• Monitor serum sodium daily 1

Step 3: Add Salt Tablets if No Response

• If sodium fails to increase or continues to decline: add NaCl 100 mEq orally three times daily 1
• Continue fluid restriction 1

Step 4: Monitoring and Adjustment

• Check sodium every 4 hours initially 1
• Adjust dose based on response, ensuring correction does not exceed 8 mmol/L per 24 hours 1
• Once stable, transition to daily monitoring 1

Common Pitfalls

• Using salt tablets in hypervolemic patients (worsens edema and ascites) 1
• Inadequate monitoring leading to overcorrection 1
• Using home-prepared salt solutions instead of pharmaceutical tablets 3
• Failing to continue fluid restriction when adding salt tablets 1
• Not distinguishing SIADH from cerebral salt wasting in neurosurgical patients 1