Can I start Risperdal (risperidone) 0.5 mg twice daily (bid) in a patient with hyponatremia (sodium level of 134)?

Risperidone Safety in Mild Hyponatremia

Risperidone 0.5 mg twice daily can be safely initiated in a patient with mild hyponatremia (sodium 134 mmol/L), as this level of hyponatremia is not a contraindication for starting risperidone therapy. 1

Assessment of Hyponatremia Severity

• Serum sodium of 134 mmol/L represents mild hyponatremia (130-134 mmol/L), which typically causes minimal symptoms 2
• Mild hyponatremia is associated with cognitive impairment, gait disturbances, and increased rates of falls and fractures, but is not immediately life-threatening 2
• A sodium level of 134 mmol/L does not meet the threshold for persistent hyponatremia (<134 mEq/L) that would be considered a clinical indicator of advanced heart failure 3

Risperidone Safety Considerations

• The FDA label for risperidone does not list hyponatremia as a contraindication for initiating therapy 4
• For patients with severe renal or hepatic impairment, the recommended starting dose is 0.5 mg twice daily, which aligns with the proposed dosing in this case 4
• While there are case reports of risperidone-induced syndrome of inappropriate antidiuretic hormone secretion (SIADH), these are rare and typically occur in combination with other medications like carbamazepine 5
• Conversely, risperidone has been reported to successfully treat polydipsia and hyponatremia in some schizophrenia patients 6

Monitoring Recommendations

• Monitor serum sodium levels regularly after initiating risperidone, especially during the first few weeks of treatment 1
• Watch for symptoms of worsening hyponatremia such as headache, nausea, confusion, or weakness 7
• If sodium levels drop below 130 mmol/L, consider:
  • Evaluating for other causes of hyponatremia 1
  • Assessing volume status to determine appropriate management 1
  • Implementing fluid restriction if appropriate 1

Risk Mitigation

• Avoid concomitant medications that may worsen hyponatremia 1
• Ensure adequate hydration without excessive fluid intake 7
• Consider lower starting doses (0.25-0.5 mg once daily) if the patient develops symptoms of hyponatremia or if sodium levels decrease further 4

Conclusion

Starting risperidone 0.5 mg twice daily is appropriate in a patient with a sodium level of 134 mmol/L, but regular monitoring of serum sodium levels is recommended to detect any potential worsening of hyponatremia.