Effects of acute renal failure and ganciclovir on the pharmacodynamics of levofloxacin-induced seizures in rats

Seizures have been reported in patients receiving fluoroquinolones, including levofloxacin (LVFX). In the present study, we investigated the effects of experimental renal failure and the concomitant treatment with ganciclovir on the pharmacodynamics of LVFX-induced seizures to identify whether these factors can alter the pharmacokinetics or the pharmacodynamics of LVFX. Male Wistar rats received an intravenous infusion of LVFX at 250, 500, or 1000 mg/h/rat until the onset of seizures, and samples of serum, brain, and cerebrospinal fluid (CSF) were obtained. The concentration of LVFX in CSF at the onset of seizures was not affected by the infusion rate, whereas that in serum and brain increased with increasing infusion rate. This suggests that the concentration of LVFX in CSF is an appropriate index of the drug concentration at the site of action. The concentration of LVFX in CSF at the onset of seizures was significantly lower in rats with renal failure than in the control rats. Pretreatment with methylguanidine, an uremic toxin, at 600 mg/h/rat for 8 min reduced the concentration of LVFX in CSF at the onset of seizures and the total body clearance of LVFX after the intravenous injection. In rats pretreated with ganciclovir at 500 mg/h/rat for 1 h, the concentration of LVFX in CSF at the onset of seizures was significantly lower than the control rats. These results suggest that renal failure and ganciclovir can be the risk factors for LVFX-induced seizures, and that they increase the sensitivity of the central nervous system to LVFX-induced seizures.

Effect of levofloxacin on serum glucose concentration in rats

To clarify the mechanism of fluoroquinolone-induced abnormalities in blood glucose, the effect of levofloxacin on serum glucose concentration was investigated in rats. Rats received an intravenous injection of levofloxacin and their arterial blood was sampled periodically. The serum glucose concentration decreased after an injection of 100 mg/kg of levofloxacin, while it increased at levofloxacin 300 mg/kg. The serum immunoreactive insulin concentration increased as the dose of levofloxacin increased. The serum epinephrine concentration was rapidly elevated by levofloxacin at 300 mg/kg. The serum histamine concentration increased after injections of levofloxacin, 200 and 300 mg/kg. Diphenhydramine (1 mg/kg) antagonized the hyperglycemia induced by 300 mg/kg of levofloxacin. In an in vitro study, the release of epinephrine from the adrenal medulla in the presence of levofloxacin was determined. Levofloxacin (300 microg/ml) did not affect epinephrine release from the adrenal medulla. Levofloxacin can induce hypoglycemia and hyperglycemia in rats. Levofloxacin can promote histamine release, leading to an increased serum epinephrine concentration and hyperglycemia.

Pharmacokinetics and pharmacological effect of recombinant human granulocyte colony-stimulating factor conjugated to poly(styrene-co-maleic acid) in rats

A new derivative of recombinant human granulocyte colony-stimulating factor (rhG-CSF) has been synthesized by conjugating rhG-CSF to poly(styrene-co-maleic acid) (poly(styrene-co-maleic acid)-rhG-CSF) to try to avoid glomerular filtration and thus potentiate the neutrophil-proliferating activity of rhG-CSF. Poly(styrene-co-maleic acid)-rhG-CSF was highly bound to bovine serum albumin (BSA) and the molecular weight of the poly(styrene-co-maleic acid)-rhG-CSF-BSA complex was estimated to be about 90000 by gel filtration. Intravenous administration of poly(styrene-co-maleic acid)-rhG-CSF to normal rats resulted in a dose-dependent increase in neutrophil count. The neutrophil-proliferating activity of poly(styrene-co-maleic acid)-rhG-CSF was about 10 times greater than that of rhG-CSF. After intravenous injection at a dose of 5 microg protein kg(-1) the total clearance of rhG-CSF fell from 71.0 to 32.1 mLh(-1) kg(-1) following poly(styrene-co-maleic acid) modification. An isolated perfusion study in rat kidney showed that the filtered fraction of rhG-CSF was reduced by conjugation with poly(styrene-co-maleic acid). These results suggest that poly(styrene-co-maleic acid)-conjugation can potentiate the neutrophil-proliferating activity of rhG-CSF by reducing, at least in part, its renal clearance.

Renal handling of tobramycin in the isolated perfused rat kidney

The renal handling of tobramycin (TOB), an aminoglycoside antibiotic (AG), was studied using a single-pass isolated perfused rat kidney with moment analysis. In the bolus administration study at tracer concentration (7.4 microM), 32% of the glomerular-filtrated TOB remained in the lumen, but no TOB was found in the vein. This ratio of the luminal uptake was reduced in a dose-dependent manner. Other aminoglycosides such as gentamicin inhibited this uptake, but tetraethylammonium and glucosamine had no effect. In addition, under the alkalinuria condition, TOB uptake was decreased to 67% of the control value. This indicated that TOB has mainly been taken into the renal epithelial cells from their luminal site and that this uptake process was saturable and specific for AGs which have more than one cationic group. The present findings should be helpful in developing a method to reduce the nephrotoxicity of AGs and to identify their toxicity mechanisms.

[Survey on clinical isolates from 13 hospitals in Akita Prefecture--changes in frequency and susceptibility of isolates by scale of hospital. Survey Group for Clinical Isolates, Chemotherapy Research Committee of Akita Prefecture]

Isolates from various clinical materials in 13 hospitals in Akita prefecture and their drug susceptibility were investigated by the Chemotherapy Research Committee of Akita Prefecture during the period from Dec., 1987 to Feb., 1988. The results were as follows: 1. The total number of isolates was 8,387, including Staphylococcus aureus (18.9%), Pseudomonas aeruginosa (10.9%), Staphylococcus epidermidis (7.3%) and Enterococcus faecalis (6.6%). S, aureus and P. aeruginosa were detected more frequently in the larger hospitals. 2. The detection frequency of S. aureus from the sputum, throat swab and pus exudate was also very high. There was a diversity in isolates from the urine and the frequency of Escherichia coli was low. More than half of the isolates from the blood were S. epidermidis and S. aureus. Many kinds of bacteria were detected from pleural fluid and ascites, but the isolate showed no particular tendency. 3. The susceptibility of S. aureus to oxacillin were variable in hospitals, and the susceptibility to cefazolin were even lower. Low susceptibility were also seen with norfloxacin. S. aureus showed the highest susceptibility to minocycline. The susceptibility was lower for inpatients than for outpatients. P. aeruginosa showed low susceptibility to cefsulodin. The number of ampicillin-resistant Haemophilus influenzae isolates tended to decrease. Enterobacter cloacae showed a low susceptibility for cephems. Serratia marcescens showed low susceptibility to many drugs. Based on the above results, we concluded that attention should be paid to S. aureus, P. aeruginosa and Enterobacter in clinical practice.