[Comparative characteristics of the methods for assessing aminoglycoside extraction with the artificial kidney tobramycin clearance and dialyzability]

Abstract

The pharmacokinetics of tobramycin after its intravenous or intramuscular injection in a dose of 80 mg for 60 minutes was studied in 8 patients with chronic glomerulonephritis in the terminal stage of chronic renal insufficiency. The drug levels wee determined in the arterial (CA) and venous (CV) blood and dialyzates (CD) during the hemodialysis (6 hours) and 13-70 hours before the hemodialysis. The antibiotic was administered simultaneously with connection of the "artificial kidney" apparatus (KIIL) or 1 hour after it. The values of the clearance (CID) and dialyzing (D) of tobramycin were calculated with the following equations: (CID)1 equals Q(CA minus CV)/CA; (CID)4 equals FCD/CA; (D)2 equals Q(CA minus CV)/(CA minus CD); (D)5 equals FCD/(CA minus CD), where Q and F are the rates of the blood and dialysate flow respectively. In all cases the values of CID and D correlated and the difference between them was not significant. During the hemodialysis the values of (CID)1 varied to a greater extent than those of (CID)4. Irrespective of the procedure for estimation of CID the above variation was not pronounced, when tobramycin was administered simultaneously with initiation of the hemodialysis or during it than long before connection of the "artificial kidney" apparatus. In this connection it is recommended that antibiotic extraction be characterized by determination of (CID)4 on the drug administration long before the initiation of the hemodialysis. When Q equals 200 ml/min and F equals 600 ml/min, the average value of CLD for tobramycin was equal to 64 ml/min and the extraction coefficient was equal to 35 per cent.