[Experimental study of the toxic effect of combinations of tobramycin and carbenicillin]

Acute toxicity of tobramycin and carbenicillin used alone and in combination was studied on albino mice. The antibiotics were combined in the following ratios: 1:15, 1:30, 1:45, 1:60, 1:75 and 1:150 (1 refers to tobramycin). The character of the toxic effect of the combinations was estimated with the Loewe graphical method and interaction indices. It was shown that interaction of tobramycin with carbenicillin in the combinations with wide ratio ranges was of an indifferent character. The toxic effect of the combinations did not reach the total toxic effect of the components used alone. It was noted that the combinations of tobramycin with carbenicillin in the ratios of 1:15, 1:30 and 1:150 were most favourable for the drug tolerance. The nephrotoxic effect of tobramycin and carbenicillin used alone and in combination was studied on albino rats. The antibiotics were administered intravenously for 5 days. It was demonstrated that the level and the character of the morphological changes in the kidneys of the rats treated with the combinations of tobramycin and carbenicillin were the same as those after the use of an analogous dose of tobramycin alone. Therefore, the nephrotoxic effect of tobramycin was not potentiated on its combined use with carbenicillin.