[Assessment of pharmacokinetic parameters of amikacin in a group of neutropenic patients in onco-hematology].

The pharmacokinetics of Amikacin were studied in 56 febrile episodes for 45 patients with severe neutropenia while using the USC*Pack PC Clinical Programs for adaptive control of their dosage regimens [223 drug levels]. The purpose of this study are: i] to estimate the pharmacokinetic parameters in this neutropenic population [56 episodes, I], ii] to evaluate the effect of the dosage regimen: once-a-day [22 episodes, II] versus bid or tid [34 episodes, III]. Patients [mean age 53.3 +/- 17.9], 23 men and 22 women, received amikacin [17.7 +/- 3.6 mg/kg/d at day 1] in a 30 minutes infusion. The mean estimated creatinine clearance [CCr] was 76 +/- 22.5 ml/min/1.73 m2 at day 1. The method used for the population modeling was the Non Parametric EM algorithm [NPEM2] which computes the complete probability density function for a 1 or a 2 compartment model. The parametrizations studied are: Clearance/Volume [CL/VOL], Elimination rate constant/Volume [Kel/VOL] and KS/VS with Kel = KS * CCr + 0.00693, VS = VOL/Weight for a 1 compartment pharmacokinetic model. The main results concerned CL and VS with: CL[I] = 4.94 +/- 2.71, CL[II] = 4.74 +/- 2.65, CL[III] = 5.14 +/- 2.75 l/h and VS[I] = 0.31 +/- 0.11, VS[II] = 0.34 +/- 0.10, VS[III] = 0.30 +/- 0.11 l/kg. Volume of distribution VS is not so large as expected and a slight difference appears between II and III. The pharmacokinetic parameters obtained for this population of neutropenic patients will be used thereafter for the daily adaptive control of Amikacine therapy in our haematologic/oncologic patients. The variability observed remains important and requires an individualization of the dosage regimen for each patient.