Bioavailability and Pharmacokinetic Features of Etoposide in Childhood Acute Lymphoblastic Leukemia Patients

The bioavailability and pharmacokinetic characteristics of etoposide were studied in 12 relapsed B-lineage acute lymphoblastic leukemia (ALL) patients after both intravenous (i.v.) infusion and oral administration. Following a 1 hour i.v. infusion of SO mg/m² etoposide, the elimination half-life ranged from 49.8 min to 509.4 min (mean ± SD = 218.6 ± 134.7 min), the MRT ranged from 71.8 to 734.9 min (mean ± SD = 315.4 ± 194.3 min) and the systemic clearance of etoposide ranged from 15.7 to 38.0 ml/min/m² (mean ± SD = 24.1 ± 7.0 ml/min/m²). The AUC ranged from 2234.9 to 5427.0 μM±min) (mean ± SD = 3827.8 ± 1069.5 μM±min) and V_c ranged from 2026.9 to 13505.2 rnl/m² (mean ± SD = 6825.4 ± 3278.5 ml/m²). The maximum plasma etoposide levels ranged from 6.0 to 28.4 μM (mean ± SD = 13.6 ± 6.3 μM). The bioavailability of oral etoposide was determined by comparing the AUC following i.v. infusion to the AUC following oral administration in the same patient. The overall bioavailability (mean ± SD) was 60.6 ± 22.4% (ranged from 17.6% to 91.2%). The elimination half-life following oral administration (mean ± SD) was 209.8 ± 196.3 min (ranged from 51.0 to 794.2 min). The time required to reach the maximum plasma etoposide concentration was 145.4 ± 118.7 min (ranged from 23.7 to 396.9 min). To our knowledge, this is the first report concerning the bioavailability of etoposide in pediatric leukemia patients. All of the other pharmacokinetic properties of etoposide in pediatric B-lineage ALL leukemia patients reported here were similar to those described previously.