The acetylating radioenzymatic assay was used for determination of levels of amikacin in serum and urine. Because of an inhibitor present in various amounts in urine, assay of amikacin in urine by this method requires added internal standards and thus is less precise than the assay in serum. Determination of the rate of plasma clearance, half-life, and volume of distribution of amikacin in 10 patients with normal renal function, four patients undergoing dialysis, and five patients with end-stage renal diseases have shown a relation of half-life (t1/2 in hr) to rate of clearance of serum creatinine (Cer) of t1/2 = 3 X Cer, the same relation as found for kanamycin and gentamicin. The apparent steady-state volume of distribution of amikacin in patients with diminished renal function is slightly, but not significantly, larger than that in normal patients; the values were 0.28 +/- 0.10 and 0.21 +/- 0.10, respectively. In normal patients, 87% of the drug is excreted by the kidney.
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