The effect of glucose on the transport of kanamycin into perilymph

Understanding the mode of transport of aminoglycoside antibiotics into the inner ear fluids is important in elucidating mechanisms of ototoxicity and the processes that permit accumulation of toxic levels of these drugs in perilymph. Concentrations of kanamycin in serum and perilymph were studied in one group of chinchillas after 250 mg/kg IM (controls). A longer time was required for peak concentrations of kanamycin to be reached in perilymph compared to serum (four hours versus one hour). This suggests a selective blood-labyrinth barrier to kanamycin. A possibility of influencing the rate of transport of this drug by alteration of a blood component has been suggested (Guth et al., 1977). The effect of glucose loading (2.0 g/kg) on the rate of transport of kanamycin into perilymph was evaluated. Kanamycin concentration in perilymph after 250 mg/kg IM was significantly lower after glucose pretreatment compared to controls, suggesting that glucose may compete with kanamycin for transport through the blood-labyrinth barrier. A number of other factors may be responsible for these findings, however, a new method of affecting the transport of ototoxic drugs into the inner ear is introduced. The present study will help to characterize the alteration of the blood-labyrinth barrier to ototoxic drugs by administering a chemical substance which may compete with the passage of the drug into the labyrinth. [This work was supported by NIH Grant No. NS-12125.]