[Absorption, distribution, metabolism and excretion of netilmicin in rats (II). Accumulation study of netilmicin after repeated administration].

Repeated administration of netilmicin (NTL), a new aminoglycoside antibiotic, to rats at daily intramuscular dose of 10 or 20 mg/kg for 22 days did not affect the plasma level and the plasma half-life of the drug. The concentrations of NTL in the kidney increased markedly after repeated administration, and reached peak level after 8 and 15 doses for 10 and 20 mg/kg, respectively. Cumulative effect of NTL after repeated dose was also observed in the liver, spleen and lung, although the peak concentrations of NTL in these organs were below 1/50 of that in the kidney. Blood and tissue levels of NTL in rats were determined after a single intramuscular administration of 14C-NTL at a dose of 20 mg/kg following 21 repeated intramuscular administrations of NTL at daily dose of 20 mg/kg. The repeated dose of NTL had no effect on the blood level-time curve of radioactivity. The concentration of NTL in the kidney determined by radioassay was about 1/3 of that determined by bioassay, whereas the half-lives in the tissue levels determined by these two assays were nearly identical with each other. The half-life in the lung determined by bioassay was almost identical to that determined by radioassay, whereas the former was rather shorter than the latter in the liver and spleen.