Etoposide: a pharmacokinetic profile including an assessment of bioavailability.

The pharmacokinetics of intravenous etoposide (50-150 mg m-2) have been studied in 17 patients. Bioavailability studies on either the capsule or intravenous (i.v.) formulation were performed in 13 patients, 7 of whom received both oral formulations given in the dose range 50-250 mg m-2. After i.v. administration the mean +/- SD half-lives were t1/2 alpha 0.62 +/- 1.01 h and t1/2 beta 6.04 +/- 2.5 h. The bioavailability of etoposide was extremely variable: for the capsule it was 38 +/- 14% (range 10-55) and for the i.v. formulation it was 53 +/- 25% (range 31-88). The i.v. formulation was not significantly better than the capsule. The results confirm the low and variable bioavailability of oral etoposide.