Pharmacokinetics of VP16-213 given by different administration methods

Plasma pharmacokinetics of VP16-213 were investigated after a 30-60 min infusion in 14 adult patients and six children. In adults the elimination half-life (T_1/2 β), plasma clearance (Cl_p) and volume of distribution (Vd) were respectively 7.05±0.67 h, 26.8±2.4 ml/min/m², and 15.7±1.8 l/m²; in children 3.37±0.5 h, 39.34±6.6 ml/min/m², and 9.97±3.7 l/m². After repeated daily doses no accumulation of VP16-213 was found in plasma. The unchanged drug found in the 24 h urine after administration amounted to 20-30% of the dose. In eight choriocarcinoma patients plasma levels of VP16-213 were measured after oral capsules and drinkable ampoules. The bioavailability compared to the i.v. route was variable, mean values being 57% for capsules and 91% for ampoules. In one further patient, with abnormal d-Xylose absorption results, VP16-213 was not detectable in plasma after the oral ampoule dose. Steady state levels investigated in three patients after 72 h continuous VP16-213 infusion (100 mg/m²/24 h) were around 2-5 μg/ml. Levels of VP16-213 were undetectable in CSF after i.v. or oral administration.