In vitro susceptibilities of 393 recent clinical isolates to WIN 49375, cefotaxime, tobramycin, and piperacillin

Analysis of fluoroquinolones in biological fluids by high-performance liquid chromatography

High-performance liquid chromatographic methods for the analysis of fluoroquinolones in biological fluids are reviewed. In particular, sample preparation and handling procedures, chromatographic conditions, and detection methods are discussed. A summary of published high-performance liquid chromatographic assays for individual fluoroquinolones is included.

Characterization of the complexation of fluoroquinolone antimicrobials with metal ions by nuclear magnetic resonance spectroscopy

The complexation of the fluoroquinolone antimicrobials is important because it has been implicated in reduced oral bioavailability and reduced antimicrobial activity when the drugs are co-administered with antacids or multi-vitamin preparations containing iron. The complexation of two model compounds, lomefloxacin and norflaxacin was studied using NMR. With aluminum ions, exchange between free and bound drug molecules was slow on the NMR time-scale. Two complexes, proposed to have stoichiometries of 2:1 and 3:1 (drug:metal) based on peak widths and variable temperature studies, were observed. The crystal structure of lomefloxacin, which shows intermolecular self association previously reported to be crucial to the drug's mode of action, is also reported. Because the metal ion complexes could not be crystallized, the crystal structure of uncomplexed lomefloxacin together with the NMR data on the aluminum complexes were used in the molecular modelling of the lomefloxacin-aluminum complexes.

Randomized, controlled trial of a 10-day course of amifloxacin versus trimethoprim-sulfamethoxazole in the treatment of acute, uncomplicated urinary tract infection. Amifloxacin Multi-Center Trial Group

We conducted a randomized controlled trial of orally administered amifloxacin versus trimethoprimsulfamethoxazole (TMP-SMX) as treatments of acute uncomplicated urinary tract infection in women. Amifloxacin at a dosage of 200 mg twice a day appeared as safe and effective as TMP-SMX, but amifloxacin at 400 mg twice a day tended to cause adverse events more frequently than did TMP-SMX.

Fluoroquinolone antimicrobial agents

The fluoroquinolones, a new class of potent orally absorbed antimicrobial agents, are reviewed, considering structure, mechanisms of action and resistance, spectrum, variables affecting activity in vitro, pharmacokinetic properties, clinical efficacy, emergence of resistance, and tolerability. The primary bacterial target is the enzyme deoxyribonucleic acid gyrase. Bacterial resistance occurs by chromosomal mutations altering deoxyribonucleic acid gyrase and decreasing drug permeation. The drugs are bactericidal and potent in vitro against members of the family Enterobacteriaceae, Haemophilus spp., and Neisseria spp., have good activity against Pseudomonas aeruginosa and staphylococci, and (with several exceptions) are less potent against streptococci and have fair to poor activity against anaerobic species. Potency in vitro decreases in the presence of low pH, magnesium ions, or urine but is little affected by different media, increased inoculum, or serum. The effects of the drugs in combination with a beta-lactam or aminoglycoside are often additive, occasionally synergistic, and rarely antagonistic. The agents are orally absorbed, require at most twice-daily dosing, and achieve high concentrations in urine, feces, and kidney and good concentrations in lung, bone, prostate, and other tissues. The drugs are efficacious in treatment of a variety of bacterial infections, including uncomplicated and complicated urinary tract infections, bacterial gastroenteritis, and gonorrhea, and show promise for therapy of prostatitis, respiratory tract infections, osteomyelitis, and cutaneous infections, particularly when caused by aerobic gram-negative bacilli. Fluoroquinolones have also proved to be efficacious for prophylaxis against travelers' diarrhea and infection with gram-negative bacilli in neutropenic patients. The drugs are effective in eliminating carriage of Neisseria meningitidis. Patient tolerability appears acceptable, with gastrointestinal or central nervous system toxicities occurring most commonly, but only rarely necessitating discontinuance of therapy. In 17 of 18 prospective, randomized, double-blind comparisons with another agent or placebo, fluoroquinolones were tolerated as well as or better than the comparison regimen. Bacterial resistance has been uncommonly documented but occurs, most notably with P. aeruginosa and Staphylococcus aureus and occasionally other species for which the therapeutic ratio is less favorable. Fluoroquinolones offer an efficacious, well-tolerated, and cost-effective alternative to parenteral therapies of selected infections.

In vitro activities of amifloxacin and two of its metabolites

Amifloxacin and two of its metabolites, N-desmethyl amifloxacin and amifloxacin N-oxide, were evaluated by a microdilution MIC susceptibility test against 500 clinical isolates and compared with ciprofloxacin, lomefloxacin, norfloxacin, aztreonam, and imipenem. Of the Staphylococcus species isolates, 208 were methicillin resistant; the MICs for 78 of the isolates of the family Enterobacteriaceae were greater than or equal to 64 micrograms of cefazolin, ampicillin, piperacillin, and mezlocillin per ml. Based on our results, amifloxacin had activity equivalent to those of norfloxacin and lomefloxacin but was less active than ciprofloxacin. The N-oxide metabolite was the least active; however, for the majority of gram-negative bacteria, N-desmethyl amifloxacin was as active as amifloxacin.

Activity of E-3846, a new fluoroquinolone, in vitro and in experimental cystitis and pyelonephritis in rats

The in vitro antibacterial activity of E-3846, a new fluoroquinolone carboxylic acid derivative with a pyrrol ring substituent at position 7, was evaluated in comparison with norfloxacin and ciprofloxacin. E-3846 was more active than the reference quinolones against Staphylococcus species, including methicillin-resistant strains. E-3846 was similar to ciprofloxacin and more active than norfloxacin against Streptococcus (Enterococcus) faecalis. In general, E-3846 was more active than norfloxacin against members of the family Enterobacteriaceae, but less active than ciprofloxacin. For Pseudomonas aeruginosa, the MICs giving 90% inhibition for E-3846, norfloxacin, and ciprofloxacin were 2, 1, and 0.25 micrograms/ml, respectively. The activity of E-3846 increased at acid pH; in contrast, acid pH caused a pronounced decrease in the activity of norfloxacin and ciprofloxacin. In vivo, E-3846 demonstrated excellent therapeutic efficacy in treating experimental S. faecalis, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Pseudomonas aeruginosa cystitis and pyelonephritis in rats.

Quinolones: pharmacology

The quinolones are synthetic antibiotics chemically related to nalidixic acid. Since its introduction, several structural analogues have been synthesized. A fundamental breakthrough was the addition of a fluorine atom. The quinolones interfere with bacterial DNA transcription by inhibiting the enzyme DNA gyrase, that so far has only been found in bacteria. The nature of the activity of the quinolones on DNA gyrase makes it highly unlikely that resistance is carried on plasmids.

Fluorinated quinolones. A review of their mode of action, antimicrobial activity, pharmacokinetics and clinical efficacy

Quinolones, chemically related to nalidixic acid, have a strong and rapid bactericidal action against Gram-negative bacteria, including Ps. aeruginosa, some Mycobacteria, Legionella and Staphylococci. Streptococci and anaerobic bacteria are usually less sensitive. The quinolones exert their bactericidal action through inhibition of the enzyme DNA gyrase. Quinolones are absorbed for 50-100% from the gastro-intestinal tract, their volume of distribution is generally high (2 l/kg) and high concentrations are reached in almost all organs. The elimination half-lives range from 4 to 14 h. The efficacy of quinolones in urinary tract infections has been shown in many studies. They also seem to be effective in many serious infections. In animal studies their efficacy was generally equal or superior to aminoglycosides. Until now only mild and infrequent side effects have been reported.

In vitro evaluation of A-56619 (difloxacin) and A-56620: new aryl-fluoroquinolones

The in vitro antibacterial potencies of A-56619 and A-56620, two new aryl-fluoroquinolones, were compared with the potency of norfloxacin against a broad spectrum of organisms. Cefotaxime, aztreonam, piperacillin, imipenem, penicillin, and gentamicin were also tested for reference purposes. The MICs required to inhibit at least 90% of the strains tested ranged from 0.25 to 4 micrograms/ml for A-56619 and from 0.06 to 0.5 microgram/ml for A-56620 for members of the Enterobacteriaceae. A-56619 was generally twofold less potent and A-56620 was twofold more potent than norfloxacin against most aerobic gram-negative bacilli, including members of the Enterobacteriaceae and Pseudomonas aeruginosa. Against indole-positive Proteus, Morganella, Providencia rettgeri, and Serratia strains, A-56619 was at least 8- to 16-fold less potent than norfloxacin. A-56619 and A-56620 were four- to eightfold more potent than norfloxacin against Staphylococcus aureus and equally potent to fourfold more potent against Streptococcus species, Haemophilus influenzae, and Neisseria gonorrhoeae. The MICs of A-56619 and A-56620 were only slightly affected by increased inoculum size or by the addition of various cations at physiologic concentrations. A-56619 was three- to fivefold less active at pH 8.0 than at pH 6.5 or 7.2. A-56620 was twofold less active at pH 6.5 than at pH 8.0 or 7.2 against members of the Enterobacteriaceae and Pseudomonas aeruginosa; similar pH variations did not affect A-56620 activity against gram-positive cocci. The potencies of A-56619, A-56620, and norfloxacin were less in urine than in Mueller-Hinton broth; however, this effect was more pronounced with norfloxacin. Human serum at a concentration of 50% caused a 4- to 64- fold decrease in the potency of A-56619 and an average 4-fold decrease in the potency of A-56620, compared with no effect on the potency of norfloxacin. A-56619, A-56620, and norfloxacin were bactericidal and, at four times the MIC, reduced the viable cell counts of Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa by approximately 99.9% within 2 h. A-56619, A-56620, and norfloxacin showed no significant synergistic activity and no antagonism when they were aminoglycoside or beta-lactam antimicrobial agents.

Antibacterial activity of amifloxacin (WIN 49, 375), a new quinolone agent

The in vitro activity of amifloxacin, a quinolone antimicrobial agent was compared with those of ciprofloxacin, enoxacin, ofloxacin and norfloxacin against gram-positive and gram-negative bacteria. Ninety percent of Escherichia coli, Klebsiella species, Aeromonas, Salmonella, Shigella, Citrobacter, Enterobacter species, Proteus mirabilis, Serratia marcescens, and Morganella morganii were inhibited by less than or equal to 0.5 microgram/ml. Amifloxacin inhibited Branhamella, Haemophilus, and Neisseria at less than or equal to 0.25 microgram/ml, and 90% of Pseudomonas aeruginosa, including gentamicin- and carbenicillin-resistant isolates, at 4 micrograms/ml. It also inhibited staphylococci, including methicillin-resistant isolates, but was less active against streptococci and Bacteroides species. Amifloxacin had in vitro activity similar to enoxacin, ofloxacin, and norfloxacin, but was less active than ciprofloxacin. Like other quinolones, it was less active at acid pH and in the presence of urine.

Metabolism and disposition of amifloxacin in laboratory animals

Sprague-Dawley rats received [14C]amifloxacin mesylate either orally or intravenously at 20 mg (base equivalent) per kg. Blood radioactivity peaked at 0.5 h after oral administration and was equivalent to 7.54 micrograms/ml for males and 6.73 micrograms/ml for females. After intravenous administration to rats, 52.5% of the dose was recovered in the urine of males and 45.3% in the urine of females within 72 h. The corresponding values after oral administration were 50.8% for males and 37.2% for females. The remainder of the dose was recovered in the feces. After intravenous administration of [14C]amifloxacin mesylate at 10 mg (base equivalent) per kg to female rhesus monkeys, 80.3% of the radioactivity was excreted in the urine at 24 h. The apparent first-order terminal elimination half-life of intact amifloxacin in plasma was 2.3 h; radioactivity in plasma was eliminated more slowly. Male rats excreted 26.2% of the dose in the urine as amifloxacin and 17.8% as the piperazinyl-N-oxide derivative of amifloxacin after intravenous administration. The corresponding amounts for female rats were 29.0% as amifloxacin and 7.8% as the piperazinyl-N-oxide metabolite. Similar excretion profiles were observed after oral administration. After intravenous administration, female monkeys excreted 54.5% of the dose in the urine as amifloxacin, 12.9% as the piperazinyl-N-desmethyl metabolite, and 5.6% as the piperazinyl-N-oxide during the first 12 h. In contrast, there was no evidence of the piperazinyl-N-desmethyl metabolite in rats.

In vitro and in vivo antibacterial activities of the fluoroquinolone WIN 49375 (amifloxacin)

WIN 49375 (amifloxacin) is a synthetic antibacterial agent of the quinolone class. It is similar in chemical structure to pefloxacin but differs by containing a methylamino, rather than an ethyl, substituent at the 1-N position. The activity of WIN 49375 in vitro was comparable to those of norfloxacin and pefloxacin against Enterobacteriaceae and generally greater than those of tobramycin and cefotaxime. WIN 49375 was more active in vitro than carbenicillin and mezlocillin against Pseudomonas aeruginosa isolates and showed moderate activity against Staphylococcus aureus, with MICs of less than or equal to 2 micrograms/ml. The in vitro activity of WIN 49375 was not markedly affected by the presence of human serum, the size of the bacterial inoculum, or changes in pH between 6 and 8. Against systemic, gram-negative bacterial infections in mice, WIN 49375 was generally less active than cefotaxime but more active than gentamicin. WIN 49548, the major piperazinyl-N-desmethyl metabolite of WIN 49375, was aa effective as the parent drug against experimental infections in mice when given parenterally. When administered orally, however, this metabolite was less potent than WIN 49375. WIN 49375 was highly active by the oral route, with 50% effective doses within two- to threefold of those obtained with parenteral medication.

Amifloxacin activity against well-defined gentamicin-resistant, gram-negative bacteria

Amifloxacin (WIN 49375) activity against a well-defined group of gentamicin-resistant gram-negative bacilli was compared with the activity of 11 other antimicrobial agents. For all strains, amifloxacin and norfloxacin were the most active agents, followed by cefotaxime and moxalactam. For Acinetobacter sp. only amifloxacin had an achievable MIC for 90% of the strains. Amifloxacin joins other newly developed DNA gyrase inhibitors as potentially useful agents for infections due to aminoglycoside-resistant gram-negative bacilli.