Nontoxic concentration of kanamycin and gentamicin for intravitreal use--evaluated by in vitro ERG.

The effects of kanamycin (KM) and gentamicin (GM) on the in-vitro electroretinogram of the albino rabbit were studied. The b-wave and oscillatory potentials (OPs) were unchanged by 0.1 mM KM. The photopic b-wave and OPs were slightly suppressed by 0.4 mM. The b-wave and OPs were not deteriorated by 23 micrograms/ml (approximately 0.05 mM) GM. The photopic b-wave and OPs were slightly suppressed by 46 micrograms/ml (approximately 0.1 mM) GM. The minimum concentration affecting the ERG was tentatively defined as the mean of the minimum concentration needed to change the ERG and the maximum concentration which induced no discernible changes in the ERG. The minimum concentration of KM and GM affecting the ERG were 0.25 mM (approximately 150 micrograms/ml) and 35 micrograms/ml (approximately 0.075 mM) respectively. The minimum concentration of KM affecting the ERG was higher than its minimum inhibitory concentration against Staphylococcus aureus and Streptococcus pneumoniae. The minimum concentration of GM affecting the ERG was higher than its minimum inhibitory concentration against Staphylococcus aureus, Streptococcus pneumoniae and Pseudomonas aeruginosa.