Neomycin Concentrations in Inner Ear Tissues and Other Organs of the Guinea Pig After Chronic Drug Administration

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Abstract
The kinetics of neomycin [an ototoxic antibiotic] entry into tissues, including those of the inner ear, was studied in the guinea pig. The animals received daily s.c. injections of 100 mg neomycin/kg body wt and were killed after 1, 3 and 6 days and 1, 2 and 3 wk. Kidney accumulated the drug rapidly and to a high level (450 .mu.g neomycin/g tissue at day 7) while levels in heart, liver, lung and spleen were lower by more than 1 order of magnitude. The drug was virtually absent from brain at all times. The salient finding was that neomycin content of cochlear tissues was relatively low. At 2 wk, concentrations in organ of Corti (0.7 .mu.g/mg protein) and lateral wall tissues (0.4 .mu.g) were similar to those in heart (0.3 .mu.g), liver (0.5 .mu.g), lung (0.8 .mu.g) and spleen (0.6 .mu.g), while the concentration in kidney was 6.8 .mu.g neomycin/mg protein. Evidently, mechanisms of drug entry are different for kidney and cochlea, and the accumulation of aminoglycosides in perilymph is apparently not reflected in tissue levels of the drug.