Can citalopram (Selective Serotonin Reuptake Inhibitor (SSRI)) cause hyponatremia (low sodium levels)?

Citalopram and Hyponatremia

Yes, Citalopram Can Cause Hyponatremia

Citalopram can definitely cause hyponatremia through the syndrome of inappropriate antidiuretic hormone secretion (SIADH), and this is a documented adverse effect in the FDA drug label that requires monitoring, especially in elderly patients. 1

Mechanism and Risk

Citalopram, like other SSRIs, can induce hyponatremia through SIADH by:

• Increasing antidiuretic hormone (ADH) secretion
• Enhancing ADH effects at the renal tubules
• Disrupting normal osmoregulation

High-Risk Populations

• Elderly patients (79% of symptomatic cases occur in patients over 70 years) 2
• Female patients (74% of cases) 2
• Patients taking diuretics, especially thiazides 1, 2
• Patients who are volume-depleted 1
• Patients on multiple medications 3

Clinical Presentation

Hyponatremia from citalopram can range from asymptomatic to severe and life-threatening:

• Mild symptoms: Headache, difficulty concentrating, memory impairment, confusion 1
• Moderate symptoms: Weakness, unsteadiness leading to falls 1
• Severe symptoms: Hallucinations, syncope, seizures, coma, respiratory arrest, and death 1, 4

Timing and Monitoring

• 84% of hyponatremia cases associated with citalopram occur within the first month of treatment 2
• Symptoms can develop rapidly - sometimes after just two doses in vulnerable patients 2
• Serum sodium levels should be monitored in high-risk patients, particularly during the first month of therapy 2, 5

Management of Citalopram-Induced Hyponatremia

1. Discontinue citalopram if symptomatic hyponatremia develops 1
2. Fluid restriction is the primary intervention for mild-moderate cases 4
3. Gradual correction of sodium levels is essential to prevent osmotic demyelination syndrome 6
   • Target correction rate: 4-6 mEq/L per 24 hours
   • Do not exceed 8 mEq/L per 24-hour period
4. Severe cases may require:
   • Hospital admission
   • Hypertonic (3%) saline for symptomatic severe hyponatremia 6
   • Initial correction of 5 mEq/L in the first hour for severe symptoms

Prevention Strategies

• Baseline serum sodium measurement before starting citalopram, especially in elderly patients 7
• Regular monitoring of sodium levels during the first month of treatment 2
• Consider alternative antidepressants in high-risk patients
• Avoid combining with other medications that can cause hyponatremia (thiazide diuretics) 2

Important Considerations

• Hyponatremia can recur when switching to other antidepressants, including those from different classes 7
• Symptoms may be mistaken for worsening depression or cognitive decline in elderly patients
• Even mild hyponatremia (126-135 mEq/L) can cause significant neurological symptoms and increase fall risk 6

Clinicians should maintain a high index of suspicion for hyponatremia when patients on citalopram present with new-onset confusion, seizures, or other neurological symptoms, particularly within the first month of treatment.