Absolute bioavailability and pharmacokinetics of oral teniposide.
The absolute bioavailability and pharmacokinetics of orally administered teniposide were investigated in 25 patients. All patients received 50 to 60 mg/m2 teniposide intravenously on day 1, before oral administration. Six patients received 60 mg/m2 as a single oral dose on day 8; 5 patients received 60 mg/m2 and 120 mg/m2 as a single oral dose on days 8 and 15, respectively; 5 patients received 120 mg/m2 and 240 mg/m2 as a single oral dose on days 8 and 15, respectively; 6 patients received 60 mg/m2 as a single oral dose on 5 consecutive days from days 8 to 12; and 3 patients received 50 mg/m2 three times a day at 6-hour intervals on day 8. The mean absolute bioavailability was 41.6% +/- 14.2% with a large interindividual variability (range, 19.7% to 71.4%) and a low intraindividual variability (range, 2.8% to 13.9%). At a dose of 240 mg/m2, the bioavailability was decreased, whereas administration of multiple doses on 1 day or 5 consecutive days increased the overall bioavailability. In conclusion, teniposide can be administered orally with a bioavailability comparable with that of etoposide. The schedule dependency of both drugs warrants investigations of oral administration for 21 or more days. A formulation of teniposide capsules of 50 mg or less would be most helpful to facilitate oral administration.