Cochlear damage resulting from kanamycin and furosemide

Permanent cochlear damage has been shown to occur in guinea pigs following the combined administration of kanamycin and furosemide. At the doses used, only a transient effect was measured with furosemide alone and no effect was detectable with kanamycin alone. This interaction results when a single subcutaneous dose of 400 mg/kg of kanamycin is followed in 2 hours by a single intravenous dose of furosemide. The dosage range for furosemide was 50 mg/kg for a just-detectable effect to 100 mg/kg for a very severe effect. Damage to the cochlea was ascertained by measures of the a.c. cochlear potential as well as surface preparation histology.

Newer aminoglycosides--amikacin and tobramycin: an in-vitro comparison with kanamycin and gentamicin

Tobramycin and amikacin are new aminoglycoside antibiotics which resemble gentamicin and kanamycin respectively in pharmacokinetic, toxicological, and some microbiological respects. Minimum inhibitory concentrations for these four antibiotics have been determined against 393 bacterial strains (13 species from eight genera) isolated from clinical materialKanamycin was the least active, 89% of the Pseudomonas aeruginosa strains being resistant. Resistance was also found in 21% of the Klebsiella aerogenes, 16% of the indoleproducing Proteus species, 4% of the E. coli and 3% of the Enterobacter spp. tested. Providenca stuartii strains were often resistant to gentamicin and tobramycin.Apart from these exceptions, however, all the organisms tested were sensitive to all four compounds, gentamicin and tobramycin usually showing the highest intrinsic activity.Amikacin was the most active compound against a selection of strains chosen because of their resistance to one or more of the aminoglycosides. Thus, amikacin represents a significant advance over kanamycin and seems to be superior to gentamicin in terms of its in-vitro properties. This is especially the case in those unusual circumstances when gentamicin-resistant strains are a problem. We suggest that amikacin warrants further investigation since it may prove to be a valuable alternative to gentamicin in the treatment of life-threatening infections.

Ethacrynic acid ototoxicity potentiation by kanamycin

The ototoxicity of ethacrynic acid and kanamycin in combination has been investigated during acute and chronic conditions of exposure. The effect of the combination of 10 mg/kg of ethacrynic acid and 100 mg/kg of kanamycin during both exposure conditions is manifested by a significantly greater drop in measured potentials than is present in the combination with lower doses of kanamycin (50 mg/kg). This effect is manifested mainly by changes in EP. The action of ethacrynic acid and kanamycin, therefore, appears to affect primarily the metabolism of the stria vascularis. According to our electrophysiological findings during acute conditions, not only simultaneous drug exposure can increase the ototoxic effect, but sequential exposure also seems to create a treatment hazard if ethacrynic acid is given following prior exposure to an ototoxic antibiotic. Therefore, a careful evaluation of the drug history in every patient should be carried out before using ethacrynic acid for treatment.

Cochlear inner and outer hair cells: functional differences

The cochlear microphonic response was measured with differential electrodes from the first and third cochlear turns of normal guinea pigs and those treated with the ototoxic drug kanamycin. Histological controls showed that the outer hair cells in treated animals were missing over the basal half of the damaged cochleas, while the inner hair cells were intact. Measurements are consistent with the hypothesis that the potentials produced by inner hair cells are proportional to the velocity of the basilar membrane, whereas potentials generated by outer hair cells (which dominate the response of normal cochleas) are proportional displacement of the basilar membrane.

Failure of urinary beta-glucuronidase activity to localize the site of urinary tract infection

The differentiation of renal from bladder bacteriuria is difficult on clinical grounds alone. To evaluate the correlation between site of infection and urinary beta-glucuronidase activity, 46 patients with well documented recurrent bacteriuria were studied by bilateral ureteral catheterization. Urinary beta-glucuronidase activity was also determined in 46 control subjects. In general, asymptomatic patients with renal bacteriuria, either unilateral or bilateral, had levels of enzyme activity in their urine comparable to patients with infection confined to the bladder and to normals. Only 4 of 25 patients with renal bacteriuria had significant elevations of urinary beta-glucuronidase. After localization of infection, 9 of 10 patients treated with kanamycin, a potentially nephrotoxic drug, developed significant elevations of urinary beta-glucuronidase. The results of these studies indicate that determination of beta-glucuronidase activity in urine is not useful in predicting the site of infection in patients with bacteriuria but may find a role in screening for early nephrotoxicity.

Streptomycin and kanamycin effect upon the vestibular sensory epithelia of the maculae sacculi and utriculi in the guinea pig

The pathological patterns of the sensory epithelia of the maculae sacculi and utriculi were investigated after streptomycin and kanamycin administration. The silver reaction method and the succinic dehydrogenase staining were used for the surface study of the sensory epithelia. The sensory cells of type I with the common nerve chalices in the striola were most vulnerable. There was no conspicuous difference of sensitivity between the type II cells inside and outside the striola. The morphological vulnerability was emphasized in the explanation for the difference in degree of sensitivity between the type I and the type II sensory cells.