Water intoxication following moderate-dose intravenous cyclophosphamide

Area of Science:

• Nephrology
• Endocrinology
• Rheumatology

Background:

• Moderate-dose intravenous cyclophosphamide (15-20 mg/kg) is increasingly used for autoimmune diseases.
• High-dose cyclophosphamide (30-50 mg/kg) for oncology and transplantation is known to cause water intolerance and intoxication.
• Previous literature has not reported water intoxication with moderate-dose cyclophosphamide.

Observation:

• The first reported case of water intoxication following moderate-dose IV cyclophosphamide is presented.
• A water challenge test ruled out underlying syndrome of inappropriate antidiuretic hormone secretion (SIADH).
• Five additional patients receiving moderate-dose IV cyclophosphamide with hypotonic fluids showed water intolerance.

Findings:

• Contrary to prior reports, moderate-dose IV cyclophosphamide can lead to water intoxication.
• Water intolerance was observed in patients receiving moderate-dose IV cyclophosphamide and hypotonic fluid hydration.
• The risk appears elevated in patients with renal insufficiency.

Implications:

• Clinicians should be vigilant for water intoxication in patients receiving moderate-dose IV cyclophosphamide, especially with hypotonic fluids.
• This finding challenges previous assumptions about the safety profile of moderate-dose cyclophosphamide regarding fluid balance.
• Careful fluid management and monitoring are crucial, particularly for vulnerable patient populations like those with renal insufficiency.