Water intoxication following low-dose intravenous cyclophosphamide

Area of Science:

• Nephrology
• Endocrinology
• Pharmacology

Background:

• Cyclophosphamide is a common treatment for severe lupus nephritis.
• Dilutional hyponatremia is a rare but serious side effect associated with cyclophosphamide therapy.
• Lupus nephritis management requires careful consideration of potential treatment complications.

Observation:

• A patient receiving low-dose intravenous cyclophosphamide (750 mg) for lupus nephritis developed symptoms of water intoxication approximately five hours post-infusion.
• Symptoms included nausea, vomiting, and general weakness.
• Initial laboratory results revealed a serum sodium concentration of 114 mEq/L, indicating severe hyponatremia.

Findings:

• The patient's severe hyponatremia was initially treated with hypertonic saline.
• Serum sodium levels rapidly normalized with simple water restriction alone, suggesting a dilutional cause.
• This case demonstrates a significant risk of water retention and subsequent hyponatremia following intravenous cyclophosphamide administration.

Implications:

• Clinicians must be vigilant for the possibility of significant water retention and dilutional hyponatremia in patients undergoing intravenous cyclophosphamide therapy, even at low doses.
• This adverse effect necessitates careful fluid management and electrolyte monitoring during treatment for lupus nephritis.
• Understanding this potential complication can guide timely intervention and prevent severe outcomes.