PHARHACOKINETIC STUDIES ON ARA-C

[Dose expression of antineoplastic drugs]

Anticancer drugs dosage are currently adjusted to body surface area. This measure is supposed to be the best morphometric parameter to adjust anticancer drug doses. However, dose adjustment to body surface area has not historically been rigorously demonstrated. We propose a method to objectively test this parameter utility. The statistical justification of drug adjustment to body surface area can use mathematical equations to be expressed. We can demonstrate that body surface area and plasmatic total clearance of a drug should be correlated to adjust dose anticancer drug to body surface area. When we test the hypothesis of body surface area and plasmatic clearance correlation for cytarabine and adriamycin we did not find any significant correlation. For these anticancer drugs, dose adjustment to body surface area increase their pharmacokinetic and efficiency variabilities. The concept of dose-intensity is probably the best justification of individual dose adjustment from plasmatic drug samples, and from pharmacokinetic and pharmacodynamic studies. The determination of the "maximal tolerable exposition" and of the "minimal effective exposition" should reduce the overexpression of toxic risks and avoid the ineffective underexpositions. However, it is difficult to precisely define these two expositions and to research the most relevant pharmacokinetic parameters to their measure. Area under curve appears to be their most appropriate expression.

Myelosuppressive effects of cytosine arabinoside (Ara-C) on growth factor-dependent human long-term bone marrow cultures (LTBMC)

Freshly isolated human mononuclear cells (5 x 10(6)) were incubated in a Dexter-type long-term bone marrow culture (LTBMC) system to study myelosuppressive effects of cytosine arabinoside (Ara-C) in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin 3 (IL-3). Differential counts (dc) of the nonadherent cell (nac) populations, starting with culture initiation, were performed weekly. After one week of simultaneous incubation of LTBMCs with either cytokine (100 ng/ml) and Ara-C (1 microgram/ml), nac numbers were markedly reduced compared to controls. Dc after week 1 of culture demonstrated significant decreases of all myeloid cell fractions except for macrophages, which remained unaffected. Growth factor-dependent LTBMCs exposed to Ara-C showed recovery of promyelocytic, metamyelocytic, and polymorphonuclear cell numbers up to control values (cultures without Ara-C exposure) in weeks 3 to 6. Intriguingly, high-proliferative, early myeloid progenitor cells (myeloblasts) appeared at high rates only in IL-3-dependent LTBMCs with and without Ara-C exposure. Nac numbers in LTBMCs exposed to Ara-C alone declined rapidly; after two weeks of culture only negligible numbers of viable nac were maintained. Plating experiments of nac in the presence of GM-CSF were performed weekly. Granulocyte-macrophage colony-forming units (CFU-GM) yields for nac from IL-3 LTBMCs were consistently higher than those for nac from GM-CSF LTBMCs. Ara-C exposure reduced CFU-GM numbers generated with nac from GM-CSF LTBMCs to 10% of GM-CSF controls (week 1). However, CFU-GM numbers grown with nac from Ara-C exposed GM-CSF-dependent LTBMCs recovered above control levels after week 3.(ABSTRACT TRUNCATED AT 250 WORDS)