Can Remeron (mirtazapine) cause hyponatremia?

Mirtazapine (Remeron) Can Cause Hyponatremia

Yes, Remeron (mirtazapine) can cause hyponatremia, which is explicitly listed as an adverse effect in the FDA drug label. 1 The risk is significant enough to warrant monitoring, especially in elderly patients and those taking diuretics.

Mechanism and Risk

Mirtazapine can cause hyponatremia through the syndrome of inappropriate antidiuretic hormone secretion (SIADH). According to the FDA drug label:

• Hyponatremia may occur as a result of treatment with serotonergic antidepressants, including mirtazapine
• Cases with serum sodium lower than 110 mmol/L have been reported
• Signs and symptoms include headache, difficulty concentrating, memory impairment, confusion, weakness, and unsteadiness 1

Incidence and Risk Factors

The incidence of mirtazapine-induced hyponatremia is approximately 3.26% (95% CI 3.06-3.45%) 2. Key risk factors include:

• Elderly patients (>60 years of age)
• Concomitant use of diuretics
• Volume-depleted patients 1
• Female gender (71.4% of reported cases) 2

Clinical Presentation

When hyponatremia occurs with mirtazapine, patients typically present with:

• Confusion (57% of cases)
• Somnolence (42% of cases)
• Altered speech (28% of cases) 2
• Mean serum sodium levels of approximately 117 mEq/L (range 113-130 mEq/L) 2
• Symptoms typically appearing around 34 days after starting treatment 2

Case Reports

Multiple case reports document mirtazapine-induced hyponatremia:

• A 67-year-old woman developed hyponatremia 5 months after switching from citalopram to mirtazapine 3
• A 72-year-old hospice patient developed severe hyponatremia (sodium 116 mmol/L) after 6 days of mirtazapine treatment 4
• Two patients (61-year-old man and 79-year-old woman) developed profound hyponatremia (sodium levels 112 and 113 mEq/L) within 7-10 days of starting mirtazapine 5

Management Recommendations

If hyponatremia develops during mirtazapine treatment:

1. Discontinue mirtazapine and institute appropriate medical intervention 1
2. Monitor serum sodium levels during recovery
3. Consider alternative antidepressants with lower risk of hyponatremia if depression treatment is still needed

Prevention

For patients starting mirtazapine:

• Obtain baseline electrolyte measurements before starting therapy, especially in patients >60 years 3
• Monitor electrolytes not only during the first weeks of treatment but throughout the course of therapy 3
• Use with caution in patients with known risk factors for hyponatremia

Clinical Pearls

• Hyponatremia can occur with doses as low as 7.5 mg daily of mirtazapine 5
• After discontinuing mirtazapine, sodium levels typically normalize within 7-11 days 5
• Despite being considered safer than SSRIs regarding hyponatremia risk, mirtazapine still poses a moderate risk 2
• Mirtazapine is listed in guidelines as a medication that "promotes sleep, appetite, and weight gain" 6, but clinicians should remain vigilant about potential electrolyte disturbances

In conclusion, while mirtazapine has a favorable side effect profile for many patients (particularly regarding sleep and appetite), clinicians should be aware of and monitor for hyponatremia, especially in high-risk populations such as the elderly.