Influence of dose in the urinary excretion of amikacin.

The urinary excretion kinetics of amikacin was studied in 28 healthy volunteers who received doses of 125, 250 and 500 mg of the antibiotic. The average percentages of the dose excreted were 67.67, 79.4 and 68.65% for each dose, respectively. The elimination constant (Ke), the urinary excretion constant (Ku) and the extra-renal excretion constant (Knr) had similar values for the three groups studied. The average value obtained for Knr showed the existence of a moderate extra-renal excretion of amikacin. A linear relationship was observed between the maximum excretion rate (Vmax) and the dose administered (D), according to the equation: Vmax (mg/h) = 3.714 + 0.207 X D (mg); r = 1.000 This relationship reveals the linear kinetics of renal excretion in the dose range studied. In view of the high urinary concentrations obtained, it is concluded that amikacin doses of 4 mg/kg/day should ensure therapeutic urinary concentrations sufficient to combat most amikacin-susceptible organisms.