Development and validation of limited sampling models for topotecan lactone pharmacokinetic studies in children.

PURPOSE: To develop and validate a pharmacokinetic limited sampling model (LSM) for intravenous and oral topotecan pharmacokinetic studies in children.
METHODS: Topotecan lactone concentration-time data from five trials were used to develop and validate LSM for intravenous and oral topotecan. Based on full sampling from one intravenous study (30 patients; 195 studies), a LSM for intravenous topotecan was determined using a modification of the D-optimality algorithm. For oral topotecan we used full sampling data from one oral topotecan study (27 patients; 47 studies) to develop an LSM. Accuracy and bias of each LSM were determined relative to the full sampling method. Predictive performance of the LSM was validated using additional data and Monte-Carlo simulations based on these data.
RESULTS: LSM for intravenous topotecan includes: 5 min, 1.5, and 2.5 h after the end of the 30 min infusion. The median accuracy (absolute predicted error) and bias (predicted error) are < or =8% and < or =6.1%, respectively. For oral topotecan, the optimal LSM includes: 15 min, 1.5, and 6 h. The median accuracy and bias are 6% and 4%, respectively.
CONCLUSIONS: Our results indicate that the optimal sampling times for the intravenous LSM for topotecan in children consist of: predose, and 5 min, 1.5, and 2.5 h after the end of infusion. For oral topotecan the sample times are predose, 15 min, 1.5, and 6 h after dose administration. These LSM are invaluable to children receiving topotecan because it minimizes inconvenience and blood collection.