White rabbits were treated with intramuscular injections of Tobramycin (TOB), Kanamycin (KM), Netilmicin (NTL) and Ribostamycin (RSM) at the dose of 50mg/kg to 200mg/kg for 30 consecutive days. The perilymph concentration of the drugs was determined with the bioassay method 4 hours after the last injection. Using the surface preparation technique hair cell damage was observed under a phase contrast microscope.
The perilymph concentration of the group RSM 200mg/kg was about twice that of the groups TOB 100mg/kg and KM 100mg/kg, although the hair cell damage of the former was much less than that of the latter. There was no difference in the perilymph concentration in all the groups, though each was given doses of 100mg/kg respectively, but the ototoxicity differed in the order of TOB>KM>>NTL≥RRSM.
It was concluded that the difference of the ototoxicity resulting from the aminoglycoside antibiotics is due to the difference of their own toxicity to hair cells and not to the difference of their accumulation in the perilymph.
