Subarachnoid administration of iohexol in cynomolgus monkeys.

A non-ionic diagnostic medium, iohexol, was administered by subarachnoid injection to groups of six cynomolgus monkeys and compared with the vehicle, physiologically normal saline, and/or saline of equal osmolality to determine its potential for increasing total protein and leucocyte levels in cerebrospinal fluid. Also investigated was the effect of repeated spinal taps not subsequently followed by the intrathecal injection of test or control articles. In the monkey, unlike man, low-level leucocyte counts were consistently observed following initial withdrawal of spinal fluid. Elevated leucocyte and total protein levels were observed in the present investigations one day to a week after intrathecal injection of radiopaque, vehicle or saline solution. Total protein returned to normal levels earlier than did leucocyte counts. However, repeated needle puncture alone was found to be sufficient to cause an elevation of leucocytes 3 to 4 times the baseline level, while inflammatory effects were observed histologically only when autopsy was performed soon after the final spinal tap.

Nephrotoxic and ototoxic effects of hydroxygentamicin in cats.

Hydroxygentamicin, an aminoglycoside antibiotic, was administered subcutaneously to cats in doses up to 160 mg base/kg daily for 10 to 13 weeks. Gentamicin and a vehicle solution were tested as positive and negative control, respectively; in one test netilmicin was also included for comparative purposes. Several parameters, including serum urea nitrogen, serum creatinine, organ/body weight ratios, serum and tissue concentrations of the antibiotics, and renal pathology, were determined to ascertain the nephrotoxic potential of the three aminoglycosides. In addition, observations for the onset of ataxia and impairment of righting reflex were made during the course of the studies to compare the vestibular ototoxic effects of the three antibiotics. Although serum urea nitrogen and serum creatinine values increased markedly in those cats which eventually died or were sacrificed moribund, these parameters in survivors were slightly but not significantly higher than controls. Serum concentrations of the drugs were proportional to the doses administered, but renal concentrations were approximately two and five times as high for netilmicin and gentamicin, respectively, as they were for equivalent doses of hydroxygentamicin. The morphological changes observed in the kidney of cats given 60 mg base/kg of hydroxygentamicin were slightly less than those seen in cats administered 10 mg base/kg of gentamicin; similarly, kidney changes in cats given netilmicin were observed approximately twice as frequently as they were in those receiving equivalent doses of hydroxygentamicin. The nephrotoxic effects of aminoglycoside antibiotics were directly related to renal drug concentration and not to serum concentration, which was a function of dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative nephrotoxicity of hydroxygentamicin and other aminoglycosides in rats.

The nephrotoxicity of hydroxygentamicin and amikacin was examined in young adult Fischer 344 rats. Serum creatinine (SCr) and urea nitrogen (BUN) levels were not significantly affected following sc injection of 80 or 160 mg/kg/day of hydroxygentamicin for 15 days. However, 250 mg/kg of amikacin produced significant increases in both parameters and in kidney/body weight ratios. The ratios were also significantly increased after 80 or 160 mg/kg of hydroxygentamicin, but kidneys of rats receiving amikacin were considerably heavier than those of rats treated with hydroxygentamicin. The antibacterial potency of 250 mg/kg of amikacin is comparable to that of 100 mg/kg of hydroxygentamicin. Additional studies, directly comparing hydroxygentamicin, a mutational biosynthetic, with gentamicin or netilmicin, all at 40, 80, and 160 mg base/kg, and incorporating renal function parameters as well as SCr, BUN, organ weight, tissue concentration, and kidney histopathology, revealed a characteristic pattern typical of aminoglycoside nephrotoxicity in mature adult male rats. In most parameters, values in rats given hydroxygentamicin or netilmicin were normal and comparable to those in controls, but kidney/body weight ratios were significantly increased at high doses. However, kidneys of rats medicated with gentamicin at comparable doses were considerably heavier than those of hydroxygentamicin-treated rats. Significant nephrotoxicity also was seen in rats given low doses of gentamicin or netilmicin. Eosinophilic granulation and vacuolization of renal proximal tubular epithelium, interstitial inflammation, and tubular dilation were observed microscopically with all three drugs in the following descending order of severity: gentamicin greater than netilmicin greater than hydroxygentamicin. The effects on proximal tubular epithelial cells following treatment with amikacin, netilmicin, or hydroxygentamicin correlated reasonably well with renal drug concentrations, but drug concentrations of gentamicin, which produced the most extensive kidney injury, were lower than those of the other three aminoglycosides. Elevated SCr or BUN were indicative of the presence of nephrosis, but early stages of tubular epithelial degeneration were not predicted by increases in BUN or SCr. Although minimal or mild nephrosis was seldom predicted by polyuria, proteinuria, or changes in osmolality, effects observed in renal function parameters usually correlated well with renal histopathology. However, a decrease in osmolality correlated best with enlarged kidneys and changes in renal morphology.

Antibacterial activities, nephrotoxicity, and ototoxicity of a new aminoglycoside, Win 42122-2.

Win 42122-2 is a new aminoglycoside antibiotic obtained from a mutant strain of Micromonospora purpurea. In vitro and in vivo comparisons of Win 42122-2 with gentamicin and amikacin revealed that Win 42122-2 generally was less active than gentamicin against Pseudomonas and many Enterobacteriacae, especially Klebsiella and indole-negative Proteus. Against most gentamicin-susceptible isolates, Win 42122-2 was more active than amikacin. Gentamicin-resistant clinical isolates were usually resistant to Win 42122-2, although it was active against certain gentamicin-resistant organisms, depending upon the aminoglycoside-modifying enzymes harbored by the organism. However, Win 42122-2 was markedly less toxic than gentamicin in subacute nephrotoxicity studies in rats, ototoxicity experiments in guinea pigs, and ataxia determinations in cats. This series of antibacterial determinations and toxicity evaluations indicated that the reduced toxicity of the antibiotic may be sufficient to provide an improved therapeutic ratio over gentamicin and other aminoglycosides, even though Win 42122-2 is less potent than gentamicin against some bacteria.