A limited sampling strategy for determining carboplatin AUC and monitoring drug dosage

There are several convincing reports showing relationships between the area under the curve of ultrafilterable concentration versus time (AUC) and pharmacodynamics of carboplatin. It is advisable, in treated patients, to check the AUC that is effectively delivered as compared with the prescribed AUC. To this end, limited sampling strategy seems to be an adequate approach since it limits the constraints of repeated blood sampling for both patients and nursing staff. A flexible limited sampling method for assessing ultrafilterable carboplatin AUC was developed. This method was based on a Bayesian estimation of carboplatin clearance using the NON linear Mixed Effect Model (NONMEN) program and a large pharmacokinetic and covariates database (103 patients). The optimal sampling design was a two-sample schedule (1 and 4 h after the end of infusion). During a prospective evaluation, it allowed an adequate estimation of carboplatin clearance with a non-significant bias (-4.5%) and a good precision (9%). In a second stage, this method was clinically applied to monitor carboplatin AUC in a group of 5 patients with metastatic germ cell tumours treated with intensified high dose carboplatin-based chemotherapy for 4 days. Dosage adjustments were performed according to daily controls of their AUC in order to obtain a total AUC of 20 mg/ml x min. By using this strategy all patients effectively received a total AUC very close to this targeted AUC, thus proving the clinical usefulness of this limited sampling method.