A possible reduction in the renal clearance of ciprofloxacin by fenbufen in rats

Effect of Fenbufen on the Entry of New Quinolones, Norfloxacin and Ofloxacin, into the Central Nervous System in Rats

The entry of two new quinolone antibacterial agents, norfloxacin and ofloxacin, into the central nervous system (CNS) of rats, and the effect of fenbufen on this was investigated. At various times after the administration of a bolus intravenous dose of norfloxacin or ofloxacin (10 mg kg−1) with or without fenbufen (20 mg kg−1), serum and cerebrospinal fluid (CSF) samples and whole brain were collected from the rats and the concentration of norfloxacin or ofloxacin in each sample was determined. Serum concentrations of both quinolones declined biexponentially with time and were significantly elevated by coadministration with fenbufen at the terminal phase. The fractions of these quinolones bound to serum protein were not altered by coadministration with fenbufen. Coadministered fenbufen raised the brain concentrations of both quinolones but did not affect their brain to serum unbound concentration ratios. In contrast, CSF to serum unbound concentration ratios as well as CSF concentrations of norfloxacin and ofloxacin were elevated by coadministration with fenbufen. Apparent diffusional clearances between blood and CSF of norfloxacin and ofloxacin estimated by the physiological model analysis increased by 1·9 and 2·6 times, respectively, after coadministration with fenbufen. These findings suggest that coadministered fenbufen may facilitate the entry of norfloxacin and ofloxacin into the CNS.

Monitoring the effects of drug treatment in rat models of disease by serum protein analysis

In this review we list from literature investigations on rat serum proteins using electrophoretic techniques in connection with drug testing. From our own research work, we provide annotated two-dimensional maps of rat serum proteins under control and experimental conditions. Emphasis is on species-specific components and on the effects of acute and chronic inflammation. We discuss our project of structural proteomics on rat serum as a minimally invasive approach to pharmacological investigation, and we outline a typical experimental plan for drug testing according to the above guidelines. We then report in detail on the results of our trials of anti-inflammatory drugs on adjuvant arthritis, an animal model of disease resembling in many aspects human rheumatoid arthritis. We demonstrate a correlation between biochemical parameters and therapeutic findings and outline the advantages of the chosen methodological approach, which proved also sensitive in revealing "side effects" of the test drugs. In an appendix we describe our experimental protocol when performing two-dimensional electrophoresis of rat serum.

Distribution of ciprofloxacin into the central nervous system in rats with acute renal or hepatic failure

Pharmacokinetic changes of various drugs have been reported in renal or hepatic failure. The present study employed ciprofloxacin, a quinolone antibiotic having neurotoxic side effects, to assess the influence of these diseases on distribution of ciprofloxacin into the central nervous system (CNS). After intravenous dosing of ciprofloxacin (10-30 mg kg(-1)), ciprofloxacin levels in plasma and brain were measured in normal rats (Wistar, male, 10-week-old) and those with acute renal and hepatic injuries which were induced by uranyl nitrate and carbon tetrachloride (CCl4), respectively. In the uranyl nitrate-treated rats, the plasma elimination half-life of ciprofloxacin was prolonged and the total body clearance was reduced when compared with those in the normal rats. Similar but smaller changes were observed in the CCl4-treated group. Brain levels of ciprofloxacin were significantly increased by both uranyl nitrate and CCl4 treatments. A proportional correlation between serum unbound levels and brain levels of ciprofloxacin was observed in the normal group. However, brain-to-serum unbound concentration ratios of ciprofloxacin were reduced in the rats with renal or hepatic failure. These results suggest that renal failure as well as hepatic failure retards elimination of ciprofloxacin from the blood, leading to elevation of the CNS level, and also that ciprofloxacin distribution in the brain is reduced in these disease states.

Efficacy of trovafloxacin in treatment of experimental staphylococcal or streptococcal endocarditis

The efficacy of trovafloxacin against Staphylococcus aureus and viridans group streptococci was investigated in vitro and in an experimental model of endocarditis. The MICs at which trovafloxacin and ciprofloxacin inhibited 90% of clinical isolates of such bacteria (MIC90s) were (i) 0.03 and 2 mg/liter, respectively, for 30 ciprofloxacin-susceptible S. aureus isolates, (ii) 32 and 128 mg/liter, respectively, for 20 ciprofloxacin-resistant S. aureus isolates, and (iii) 0.25 and 8 mg/liter, respectively, for 28 viridans group streptococci. Rats with aortic vegetations were infected with either of two ciprofloxacin-susceptible but methicillin-resistant S. aureus strains (strains COL and P8), one penicillin-susceptible Streptococcus sanguis strain, or one penicillin-resistant Streptococcus mitis strain. Rats were treated for 3 or 5 days with doses that resulted in kinetics that simulated those achieved in humans with trovafloxacin (200 mg orally once a day), ciprofloxacin (750 mg orally twice a day), vancomycin (1 g intravenously twice a day), or ceftriaxone (2 g intravenously once a day). Against the staphylococci, the activities of both trovafloxacin and ciprofloxacin were equivalent to that of vancomycin, and treatment of endocarditis with these drugs was successful (P < 0.05). However, ciprofloxacin selected for resistant derivatives in vitro and in vivo, whereas trovafloxacin was 10 to 100 times less prone than ciprofloxacin to select for resistance in vitro and did not select for resistance in vivo. Against the two streptococcal isolates, trovafloxacin significantly (P < 0.05) decreased bacterial counts in the vegetations but was less effective than the control drug, ceftriaxone. Thus, a simulated oral dose of trovafloxacin (200 mg per day) was effective against ciprofloxacin-susceptible staphylococci and was less likely than ciprofloxacin to select for resistance. The simulated oral dose of trovafloxacin also had some activity against streptococcal endocarditis, but optimal treatment of infections caused by such organisms might require higher doses of the drug.

Fenbufen pretreatment potentiates the anticonvulsant activity of CPPene and NBQX in DBA/2 mice

The anticonvulsant activity of 3-((+/-)-2-carboxypiperazin-4-yl)-1-propenyl-1-phosphonic acid (CPPene) and 2,3-dihydroxy-6-nitro-7-sulphamoyl-benzo(F)quinoxoline (NBQX), two excitatory amino acid antagonists, was studied against audiogenic seizures in DBA/2 mice, following intraperitoneal (i.p.) or intracerebroventricular (i.c.v.) administration. Maximal anticonvulsant protection was observed 15-30 min following NBQX and 45-180 min after CPPene. Coadministration with fenbufen (20 mg kg-1, i.p.), a non-steroidal anti-inflammatory agent, enhanced and prolonged the anticonvulsant actions of CPPene and NBQX and also potentiated and prolonged the impairment of rotarod performance. The enhancement of the anticonvulsant activity and the prolonged impairment of rotarod performance suggests that fenbufen may have some pharmacokinetic interactions with CPPene and NBQX and that fenbufen is able to increase the brain levels of these excitatory amino acid antagonists. In particular, fenbufen was able to exert a major degree of potentiation of effects of NBQX rather than those of CPPene, suggesting that the chemical structures of these excitatory amino acid antagonists are responsible for the different degree of interactions between CPPene or NBQX and fenbufen. NBQX appears to have a notable similarity with quinolones whilst CPPene does not. Additionally fenbufen may displace CPPene and NBQX from plasma binding sites or inhibit the renal excretion. The present data are also consistent with previous studies showing pharmacokinetic interactions between fenbufen and quinolones.

Effect of famotidine on ciprofloxacin pharmacokinetics after single intravenous and oral doses in rats

The effect of intravenous (3.5 mg/kg) and oral (5 mg/kg) famotidine on ciprofloxacin pharmacokinetics after single (i.v.) intravenous (5 mg/kg) and oral (20 mg/kg) doses were examined in the rat. Famotidine co-administration significantly increased the terminal elimination half-life of ciprofloxacin (54% and 29% following i.v. and oral administration, respectively) and tended to reduce the total body clearance by 27% and 34% following i.v. and oral routes, respectively. The area under the plasma concentration-time curve and the mean residence time in the body after i.v. and oral doses were significantly increased following famotidine co-administration. No changes in the steady-state apparent volume of distribution was observed after i.v. administration. The maximum plasma concentration and the time to peak concentration after oral dosing were also unaffected. These results suggest a possible reduction in the total clearance of ciprofloxacin, owing to inhibition of its renal tubular excretion by famotidine. Further studies are warranted to determine whether this interaction occurs in humans.

Involvement of inhibitory and excitatory neurotransmitters in levofloxacin- and ciprofloxacin-induced convulsions in mice

We studied the effects of gamma-aminobutyric acid (GABA)-benzodiazepine receptor agonists and glutamate receptor antagonists on levofloxacin (LVFX)- and ciprofloxacin (CPFX)-induced convulsions using intrathecal (i.t.) injections in mice. We also studied the effects of these agonists and antagonists on exacerbated convulsions induced by coadministration of the quinolone with 4-biphenylacetic acid (BPAA). The agonists or antagonists were injected i.t. 5 min and BPAA was administered orally 30 min before a single i.t. injection of the quinolone (10 microliters per animal). The animals were observed for clonic convulsion and death, and latency times to the appearance of convulsion were determined. Among the agonists, baclofen showed marked inhibition of both LVFX- and CPFX-induced convulsions, while other compounds such as GABA, muscimol, diazepam, and 3-aminopropylphosphonic acid had slight effects. Among the antagonists, kynurenic acid showed the strongest inhibition of convulsions caused by all doses of LVFX and CPFX and prolonged latency times; gamma-glutamyl-aminomethylsulfonic acid (GAMS) also markedly inhibited convulsions. The antagonists D-AP-5, AP-7, and 6,7-dinitroquinoxaline-2,3-dione (DNQX) had slight effects. Additionally, GAMS, DNQX, and MK-801 significantly lowered the incidence of death in the groups treated with CPFX. The enhanced convulsive activities of LVFX or CPFX by pretreatment with BPAA were clearly blocked by baclofen, kynurenic acid, GAMS, and DNQX. D-AP-5 and AP-7 also showed clear effects on the activity of LVFX. These results suggest that LVFX has fewer effects on the brains than CPFX and that convulsions induced by these quinolones alone and by these quinolones administered with BPAA may be mediated largely through glutamate and GABA(B) rather than GABA(A) receptors in mice.