Water intoxication induced by low-dose cyclophosphamide in two patients with systemic lupus erythematosus

Abstract

Cyclophosphamide(CY) is an alkylating agent used to treat a variety of autoimmune disorders.Water intoxication is a well-known complication of high-dose intravenous (i.v.) CY, but is rare in patients treated with low dose i.v. CY. We describe two patients with lupus nephritis and water intoxication following low dose i.v. CY. The first patient was treated with oral prednisolone and azathioprine for eight weeks with inadequate response and persistent renal inflammatory activity. Eight hours after the first i.v. CY pulse she had a grand mal seizure. The second patient had WHO class III lupus nephritis, and after a single i.v. CY pulse developed vomiting, diarrhoeaand grand mal seizures.They were both fluid-restrictedand their serum sodium levels returned to normal. In conclusion, even at low doses i.v. CY may induce hyponatremiarelated to inappropriateantidiuretichormone secretion. This potentially life-threateningcomplication of i.v. CY could be minimized by avoidance of overhydrationfollowing pulse i.v. CY.