Comparison of the intrarenal disposition of tobramycin and gentamicin: Therapeutic and toxicologic answers

In healthy kidneys aminoglycoside drugs demonstrate remarkable renal cortical accumulation characteristics. In our studies the highest levels occurred with the most nephrotoxic agent, neomycin, followed by gentamicin b tobramycin b streptomycin. Within the therapeutic serum range of 1 to 8 μg/ml, gentamicin consistently demonstrated cortical concentrations greater than those of tobramycin. Cortical cellular uptake was saturable at high serum concentrations and could be blocked by the concurrent administration of amino acids. In severely diseased human kidneys the tissue accumulation of the aminoglycosides was significantly reduced. However, tobramycin manifested slight but significantly higher levels than gentamicin. This is of therapeutic importance in drug selection for indolent infections complicating pre-existing renal disease.