Delayed elimination of SN-38 in cancer patients with severe renal failure.
ABSTRACT This prospective study is designed to examine the effects of severe renal failure on the pharmacokinetics of irinotecan. The pharmacokinetics of irinotecan, 7-ethyl-10-hydroxycamptothecin (SN-38), and SN-38 glucuronide (SN-38G) in three cancer patients with severe renal failure [creatinine clearance (Ccr) ≤ 20 ml/min] who were undergoing dialysis and received 100 mg/m(2) irinotecan as monotherapy were prospectively compared with those in five cancer patients with normal renal function (Ccr ≥ 60 ml/min). To ensure that the subjects had similar genetic backgrounds of UDP-glucuronosyltransferase (UGT) 1A1, patients with UGT1A1*1/*1, *1/*6, or *1/*28 were enrolled. The estimated terminal elimination rate constant of SN-38 in patients undergoing dialysis was approximately one tenth of that in patients with normal renal function (P = 0.025). Approximately 50% of SN-38 was dialyzed with a 2.1-m(2) dialysis membrane, whereas 27% was dialyzed with a 1.5-m(2) membrane. Our results showed that the elimination of SN-38 was significantly delayed in patients with severe renal failure compared with patients with normal renal function. We demonstrated that SN-38 was partly dialyzed.