[Pharmacokinetics and individual dose adjustment of carboplatin]

Abstract

Carboplatin differs from cisplatin by its pharmacokinetics and toxicity profile. Carboplatin is mainly eliminated by the kidneys and its dose-limiting toxicity is the bone marrow suppression. Myelosuppression of carboplatin is more closely correlated with the area under the curve (AUC) of ultrafiltrable plasma concentration versus time to which a patient is exposed, than it is with the administered dose. Similar relationships have been shown between AUC and antitumour effect, although they are in a smaller number and less close. Several methods of dosage individualisation a priori (before carboplatin administration) have been proposed. Since carboplatin is often prescribed to patients with altered renal functions, this dose optimisation is particularly justified. Dose individualisation is based on both equations allowing to predict the patient carboplatin clearance and the choice of target AUC. The different equations proposed are based on direct measurement of the renal filtration glomerular rate or on patient demographic and biological characteristics such as weight and serum creatinine. The respective advantages and limits of these equations are now well known. However, the values of optimal AUC that depend on cytotoxic drugs combined to carboplatin and the patient hematopoietic status, are not precisely determined for each protocol of chemotherapy. When carboplatin is given by reiterated administrations within each course, it is possible to adjust the last doses according to a limited number of blood samples following the first infusion and a Bayesian analysis of the observed plasma concentrations. These methodologies are more complex, but they may be useful for the intensification protocols. Carboplatin is still the only cytotoxic drug for which dose is individualised not according to the body surface area but according to pharmacokinetic parameters.