Determination of Plasma Concentrations of Amikacin in Patients of an Intensive Care Unit

Abstract

Considering the low therapeutic index of the amino-glycosides it is mandatory to monitor serum concentrations (SC) either to obtain therapeutic levels or to avoid toxic levels.

The SC of amikacin (AMK) was evaluated in 24 inpatients in an intensive care unit of Hospital São João, mean age (± SD) 45.5±18.57 years. In 62.5% of the patients it was shown that SC (mean ± SD, 16.87±1.62) was inferior to the therapeutic range. In 33.3% the values (SC 25.85±3.77) were within the therapeutic window (> 20 μg/ml; < 35 μg/ml). Only 1 patient attained toxic levels (> 35 μg/ml). In 4 of the patients with initial SC< 20μg/ml, dosage was adjusted and thereafter therapeutic value was obtained (SC 24.65 ± 3.38). The relation between the administered dose and the dosage usually recommended (weight × 15mg/day) was calculated. In the majority of our patients (the so-called “critically ill patients”) the recommended dosages of AMK need to be increased in order to get the desired SC. In the population of this study a dosage of about 120% relative to the initial recommended dosage was necessary.