Can citalopram (Selective Serotonin Reuptake Inhibitor - SSRI) cause hyponatremia?

Citalopram and Hyponatremia

Citalopram can definitely cause hyponatremia, particularly in elderly patients, through the syndrome of inappropriate antidiuretic hormone secretion (SIADH) mechanism, and requires monitoring of sodium levels especially during the first month of treatment.

Mechanism and Risk

Citalopram, like other Selective Serotonin Reuptake Inhibitors (SSRIs), can cause hyponatremia through the syndrome of inappropriate antidiuretic hormone secretion (SIADH) 1. This occurs when there is excessive release of antidiuretic hormone leading to water retention and dilutional hyponatremia.

High-Risk Populations:

• Elderly patients (particularly those over 70 years) 2
• Female patients (though recent research shows males may also be at significant risk) 3
• Lower baseline sodium levels 3
• Patients taking diuretics, especially thiazides 1, 3
• Volume-depleted patients 1

Incidence and Timing

• Approximately 16.5% of patients starting citalopram develop hyponatremia 3
• 84% of cases occur within the first month of treatment 2
• Hyponatremia can develop after as few as two doses in vulnerable patients 2

Clinical Presentation

Hyponatremia due to citalopram may present with:

• Headache
• Difficulty concentrating
• Memory impairment
• Confusion
• Weakness
• Unsteadiness (potentially leading to falls)

In severe cases:

• Hallucinations
• Syncope
• Seizures
• Coma
• Respiratory arrest
• Death 1

Monitoring and Prevention

1. Baseline sodium measurement before starting citalopram
2. Regular monitoring of serum sodium, particularly:
   • During the first month of treatment
   • In elderly patients
   • In patients taking diuretics
   • In patients with low baseline sodium
3. Lower starting doses in elderly patients (10mg daily) 4
4. Maximum dose limitations:
   • 20mg/day in patients over 60 years 4
   • 40mg/day maximum for adults 4

Management of Citalopram-Induced Hyponatremia

If hyponatremia develops:

1. Discontinue citalopram 1
2. Implement fluid restriction 5
3. Monitor sodium levels until normalization
4. Consider alternative antidepressants with lower risk of hyponatremia if needed

Important Considerations

• Symptoms of hyponatremia may mimic worsening depression or other psychiatric conditions
• Rapid correction of severe hyponatremia must be avoided due to risk of osmotic demyelination syndrome 6
• Concomitant medications that can cause hyponatremia (such as diuretics) increase the risk 2
• Polymedication increases the risk of developing hyponatremia 2

Alternative Antidepressants

If a patient has experienced citalopram-induced hyponatremia or is at high risk:

• Consider mirtazapine or trazodone which may have lower risk profiles in elderly patients 4
• If an SSRI is still preferred, careful monitoring of sodium levels is essential

Conclusion

Citalopram-induced hyponatremia is a significant adverse effect that requires vigilance, particularly in elderly patients. Close monitoring of serum sodium levels, especially during the first month of therapy, can help identify this complication early and prevent serious consequences.