Although limited data are available about cyclophosphamide disposition in patients with renal insufficiency, nothing has been reported in anephric patients. We characterized cyclophosphamide pharmacokinetics in an anephric child with bilateral Wilms tumor, both on (day 1) and off (day 2) hemodialysis. The median cyclophosphamide clearance on and off hemodialysis was 5.34 and 3.82 L/hr*m(2), respectively, demonstrating elimination of cyclophosphamide in this anephric child. The off hemodialysis clearance was similar to that in children with normal renal function. Hydroxycyclophosphamide (HCY) AUC was 20.6 and 8.77 microM*hr on and off hemodialysis. Carboxyethylphosphoramide mustard (CEPM) AUC obtained on hemodialysis (i.e., 194 microM*hr) was similar to that in children with normal renal function, although an elevated CEPM AUC was observed when hemodialysis was not received (i.e., 383 microM*hr). With the recent findings that clinical outcomes are related to CEPM AUC, further data are needed regarding the pharmacokinetics of cyclophosphamide and relevant metabolites in anephric children.