Population pharmacokinetic of total cisplatinum: Application to adaptative dosing with feed back in testicular cancer patient

2043

Background: Cisplatinum (CDDP) is major drug used in germ cell testicular cancer. Pharmacokinetics (PK)/pharmacodynamics relationships have been described after measurement of free CDDP in plasma, and subsequently, CDDP administration is standardized using body surface area (BSA) for only dose tailoring. Methods: Based on a rapid assay of total CDDP in plasma we have developed an alternative 120-hours continuous infusion schedule, coupled to a Bayesian adaptive dosing strategy. We present a retrospective evaluation of this schedule in 19 patients (66 courses) treated for testicular germ cell tumors. A NONMEM analysis was then performed to identify the covariates associated with total CDDP clearance. We compared doses effectively given to our patients with the ones calculated with BSA. Results: Plasma samples were analyzed to allow real-time Bayesian estimation of individual PK parameters with subsequent daily dose adjustment in order to reach a target Cend of 1.95 mg/l of total platinum. No statistical difference was observed between experimental and target values, and Cend adjustment was achieved with an overall 6.6% precision, a performance to be compared with the 54% inter-patient variability observed in drug clearance. Course number (CNB) was the only covariate to be correlated with total CDDP clearance. A weaker correlation was found with BSA, and only when considering first courses. Moreover, doses of CDDP administered were significantly higher than the ones classically normalized with BSA, thus leading to an overall greater exposure in our patients. Only few severe toxicities were reported, and all of the patients presented in this study were still alive and disease-free after a follow up of up to 15 years. Conclusions: Our alternative schedule is a convenient and safe strategy to ensure administration of optimal dose-intensity of CDDP, with limited side-effects in patients with testicular cancer. We demonstrate a linear correlation between course number and decrease of CDDP clearance (25%). This, highlights the critical importance of total drug accumulation on CDDP PK when several infusions are to be administered in a row, and therefore the need for developing dynamic dose individualization strategies that includes CNB.

No significant financial relationships to disclose.

Seventy-two-hour stability of Taxol in 5% dextrose or 0.9% sodium chloride in Viaflo, Freeflex, Ecoflac and Macoflex N non-PVC bags

BACKGROUND AND OBJECTIVES

Taxol (paclitaxel), is an antimicrotubule agent widely prescribed for the treatment of many tumoral diseases. Taxol must be used in non-polyvinyl chloride bags, diluted to concentrations of 0.3-1.2 mg/mL in 5% dextrose or in 0.9% sodium chloride. Under these conditions, Taxol is chemically and physically stable for 27 h at 25 degrees C. The aim of the study was to evaluate the 72-h stability of Taxol under common clinical use conditions.

METHODS

Taxol was diluted with 5% dextrose and 0.9% sodium chloride to final concentrations of 0.3 and 1.2 mg/mL in four polyolefin bags (Viaflo, Freeflex, Ecoflac and Macoflex N). Taxol-stability, was assessed by turbidimetry and by high-performance liquid chromatography using solutions stored in the dark, over 72 h at +4 degrees C.

RESULTS

No haze, turbidity, or precipitate was observed. Paclitaxel concentration remained above 95% of the initial value whatever the solvent or container used.

CONCLUSION

Paclitaxel at 0.3 and 1.2 mg/mL in 5% dextrose and in 0.9% sodium chloride is stable in Viaflo, Freeflex, Ecoflac and Macoflex N non-PVC bags for 72 h in the dark at +4 degrees C. The longer stability should make the use of Taxol in clinical practice easier.