Pharmacokinetics of ciprofloxacin with reference to other fluorinated quinolones

Pharmacokinetics of pefloxacin and its interaction with cyclosporin A, a P-glycoprotein modulator, in rat blood, brain and bile, using simultaneous microdialysis

1. In vivo microdialysis with HPLC was used to investigate the pharmacokinetics of pefloxacin and its interaction with cyclosporin A. Microdialysis probes were inserted into the jugular vein/right atrium, the striatum and the bile duct of male Sprague-Dawley rats. Biological fluid sampling thereby allowed the simultaneous determination of pefloxacin levels in blood, brain and bile. 2. Following pefloxacin administration, the brain-to-blood coefficient of distribution was 0.036. This was calculated by dividing the area under the concentration curve (AUC) of pefloxacin in brain by its AUC in blood (k=AUC(brain)/AUC(blood)). 3. When the P-glycoprotein cyclosporin A (10 mg kg(-1)) was co-administered with pefloxacin (10 mg kg(-1)), the AUC and the mean residence time in rat blood did not differ significantly (P>0.05). Similarly, the pharmacokinetics of pefloxacin in rat brain was not affected by the presence of cyclosporin A. 4. The AUC of unbound pefloxacin in bile was significantly greater than that in blood. The disposition of pefloxacin in rat bile shows a slow elimination phase following a peak concentration 30 min after pefloxacin administration (10 mg kg(-1), i.v.). The bile-to-blood coefficient of distribution (k=AUC(bile)/AUC(blood)) was 1.53. 5. The results indicated that pefloxacin was able to penetrate the blood-brain barrier and that the concentration in bile was greater than that in the blood, suggesting active biliary excretion of pefloxacin. Current data obtained from rats show no significant impact of cyclosporin A on the pharmacokinetics of pefloxacin in rat blood and brain when administered by concomitant i.v. bolus.

Influence of renal failure on intestinal clearance of ciprofloxacin in rats

Following intravenous doses, ciprofloxacin pharmacokinetics in control and nephrectomized rats were studied. There were no differences between control and nephrectomized rats for area under the concentration-time curve in plasma or biliary clearance. The intestinal clearance of ciprofloxacin was increased in nephrectomized rats. Intestinal elimination seems to compensate partially for the decrease in urinary excretion of ciprofloxacin in nephrectomized rats.

Influence of renal failure on ciprofloxacin pharmacokinetics in rats

Ciprofloxacin pharmacokinetics have been shown to be modified in patients with renal failure (e.g., the intestinal secretion of ciprofloxacin is increased). This study investigated the influence of renal failure on the pharmacokinetics of ciprofloxacin following oral and parenteral administration to rats of a dose of 50 mg/kg of body weight. After parenteral administration, only renal clearance (CLR) was reduced in nephrectomized rats (5.3+/-1.4 versus 17.8+/-4.7 ml/min/kg, P < 0.01, nephrectomized versus control rats). However, nonrenal clearance was increased in nephrectomized rats (32+/-4 versus 15+/-5 ml/min/kg, P < 0.01, nephrectomized versus control rats), suggesting compensatory mechanisms for reduced renal function. After oral administration, apparent total clearance and CLR were reduced (P < 0.01) in nephrectomized rats (117+/-25 and 6.8+/-4.4 ml/min/kg, respectively) compared with the values for control rats (185+/-9 and 22.6+/-5.3 ml/min/kg, respectively) and the area under the concentration-time curve was higher (P < 0.01) for nephrectomized rats (436.3+/-90.5 mg. min/liter) than for control rats (271.3+/-14.3 mg.min/liter). Terminal elimination half lives in the two groups remained constant after oral and parenteral administration. These results suggest an increased bioavailability of ciprofloxacin in nephrectomized rats, which was confirmed by a nonlinear mixed-effect model.

Hepatobiliary elimination of temafloxacin

The biliary excretion of temafloxacin and temafloxacin glucuronide was characterised in this study after administration of a single oral temafloxacin 600mg dose to 8 patients with T-tube drainage of the common bile duct inserted after cholecystectomy or choledochotomy. High performance liquid chromatographic analyses of plasma, urine and bile samples collected during the 72h after temafloxacin administration showed that biliary concentrations of unchanged temafloxacin followed a time-course parallel to plasma concentrations but were 5- to 10-fold higher. Biliary temafloxacin peak concentrations ranged from 18.74 to 64.35 mg/L and time to peak concentrations from 0.71 to 10.23h. Mean hepatobiliary clearance of temafloxacin was 3.10 ml/min (0.19 L/h) when calculated for the unchanged drug and 1.43 ml/min (0.09 L/h) when calculated for its biliary excretion as glucuronic acid conjugates. Patients with higher bile production had markedly higher clearance of both temafloxacin and temafloxacin glucuronide. The elimination time-course of the conjugate in bile generally paralleled those of temafloxacin in bile and plasma, although there was a lag in the rate of appearance of the conjugate in bile. Biliary excretion of unchanged temafloxacin and temafloxacin glucuronide accounted for approximately 2.2 and 1% of the administered dose, respectively. Thus, it appears that hepatobiliary elimination of temafloxacin and its glucuronide acid accounts for only a small fraction of total temafloxacin clearance. Nonetheless, concentrations attained in the bile are far above the minimum inhibitory concentration values of pathogens relevant in biliary tract infections.