A series of novel 1-alkoxy-1,4-dihydro-4-oxo-3-quinolinecarboxylic acids was synthesized and screened as antimicrobial agents. The most active compounds in vitro against gram-negative microorganisms and Staphylococcus aureus were 1,4-dihydro-1-methoxy-6,7-methylenedioxy-4-oxo-3-quinolinecarboxylic acid (22), 1,2,6,9-tetrahydro-6-methoxy-9-oxofuro[3,2-f]quinoline-8-carboxylic acid (30, and 2,3,6,9-tetrahydro-6-methoxy-3-methyl -2,9-dioxothiazolo [5,4-f]quinoline-8-carboxylic acid (34). These compounds had antigram-negative activity comparable to that of the corresponding N-ethyl derivatives 1, 2, and 4. Their serum levels and urinary recovery rates in rats, however, were significantly improved relative to the latter compounds (1,2, and 4).

A new chemotherapeutic agent, AB206, shows potent antibacterial activity against gram-negative bacteria, including most of the nalidixic acid-resistant strains tested. It strongly inhibits deoxyribonucleic acid (DNA) synthesis in Escherichia coli, but only slightly inhibits ribonucleic acid and protein synthesis. Its activity on DNA synthesis in vivo and in vitro is greater than that of nalidixic acid. AB206 also strongly inhibits in vivo DNA synthesis in nalidixic acid-susceptible and -resistant clinical isolates of Proteus and Serratia. AB206 shows high penetrability into E. coli cells, as demonstrated by antibacterial activity with or without ethylenediaminetetraacetic acid, inhibition of in vivo and in vitro DNA synthesis, and uptake of the drug into cells, as compared to nalidixic acid. It appears that the high antibacterial activity of AB206 may be explained both by its potent inhibitory action against DNA synthesis and also by its high penetrability into bacterial cells.

JapanMiloxacin, a synthetic antibacterial agent structurally related to oxolinic acid, has a broad spectrum of activity in vitro against gram-negative bacteria and considerable activity in vivo against infections with these bacteria. These observations led to studies on the absorption and excretion of miloxacin in mice, rats, and dogs after administration of a single oral dose. Studies on oxolinic acid have been included for comparison. Peak serum levels of miloxacin, attained 1 h after administration of 20, 50, and 100 mg/kg to rats and dogs, were approximately 20, 40, and 60 ,Ag/ml, respectively. Peak levels in mice receiving the same dose were 15, 60, and 80 ,ug/ml at 0.5 h. Peak serum levels of oxolinic acid were attained 0.5 to 1 h later than the above times at comparable doses and were one-half to onefourth those of miloxacin. Urinary recovery of miloxacin at the above doses ranged from 3.2 to 6.5% during the 24-h posttreatment period. Recoveries of oxolinic acid were one-half to one-fifth those of miloxacin. At a 50-mg/kg dose, rats excreted 4.6% of the miloxacin in bile in the 20-h posttreatment period.acid, closely related to oxolinic acid (5) in structure, has exhibited a broad spectrum of antibacterial activity in vitro and is especially active against gram-negative bacteria (3). Miloxacin also has significant activity in single-or two-dose regimens against infections with Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Proteus vulgaris, or Serratia marcescens in mice (3). These findings led to studies of the absorption and urinary excretion of this compound after administration of single oral doses to mice, rats, and beagle dogs and the biliary elimination of this compound in rats. Studies on the absorption and urinary excretion of oxolinic acid have been included for comparison. MATERIALS AND METHODSTest compounds. The preparations of miloxacin and oxolinic acid used in the current experiments were synthesized in our laboratory (1, 5). The structures and purities were confirmed by comparison to authentic compounds by infrared, nuclear magnetic resonance, and mass spectra and thin-layer chromatography.Drug administration. Micronized samples of miloxacin and oxolinic acid were suspended in 0.5% aqueous carboxymethylcellulose solution and administered within 1 h of preparation. Mice, rats, and beagle dogs were fasted for 12 to 14 h before administration of single doses of 20, 50, and 100 mg/kg by gavage. The dosed animals were held in metabolism cages suitable for each species; food was withheld for 4 h after administration.Studies in mice. A total of 360 male ICR mice weighing approximately 20 g were used. Fifteen groups, of 10 mice each, were dosed with miloxacin (5 groups for each dose). Animals were decapitated 0.5, 1, 2, 4, and 8 h after dosage. Blood from each group was pooled, kept at room temperature for 0.5 h, and centrifuged at 2,500 rpm to obtain serum, which was immediately frozen and stored at -20°C until assayed. Three groups of 10 mice treated with miloxacin (one group for ea...

The chemotherapeutic properties of miloxacin (5,8-dihydro-5-methoxy-8-oxo-2H-1,3-dioxolo-[4,5-g] As shown in Fig. 1, miloxacin [5,8-dihydro-5-methoxy-8-oxo-2H-1,3-dioxolo-[4,5-g]quinoline-7-carboxylic acid], synthesized in our laboratories (1), is a quinoline derivative closely related structurally to oxolinic acid (4) and reported to be much more active against gram-negative bacteria in vitro and in vivo than nalidixic acid.This report compares the in vitro and in vivo activities of miloxacin against various organisms with the activities of oxolinic acid and nalidixic acid. MATERIALS AND METHODSAntimicrobial agents. Miloxacin and oxolinic acid were synthesized in our laboratories. Nalidixic acid was extracted with chloroform from commercial tablets and washed with ethanol; its melting point was 225 to 231°C. Each drug was dissolved in 1% sodium carbonate solution in a concentration of 5 mg/ml. These stock solutions were diluted with M/15 phosphate buffer (pH 7.4) before use.Strains. Of the strains examined in this study, the clinical isolates were obtained from patients in Osaka National Hospital and practicing doctors in Kyoto. All standard strains were maintained in our laboratories.Susceptibility test. The antibacterial activities of miloxacin, oxolinic acid, and nalidixic acid were evaluated by a routine agar plate dilution method. The clinical strains in Table 1 except for Haemophilus influenzae and the laboratory standard strains of Enterobacteriaceae, streptococci, bacilli, and corynebacteria in Table 2 were grown overnight at 37°C in tryptic soy broth (Nissui) yielding a viable cell count of about 109 cells per ml. All strains of H. influenzae were grown overnight at 37°C in chocolate broth yielding about 107 viable cells per ml. All strains of anaerobes were grown overnight in GAM broth (Nissui) at 370C to yield 109 cells per ml. Strains of Neisseria were grown for 2 days on a rabbit blood agar plate, the growth being removed just before use and resuspended in tryptic soy broth so as to yield a viable cell count of 10' cells per ml. Two strains of Mycoplasma were grown for two days in PPLO broth (Difco) supplemented by 10% yeast extract and 20% horse serum yielding 106 cells per ml.A 1-jd amount of undiluted culture was transferred to the surface of the drug-containing agar by a Typing Apparatus (Mutoh Kikai Co., Ltd., Tokyo, Japan) multipoint inoculating device, yielding final inocula of 103 Mycoplasma, 104 Haemophilus and Neisseria, and 105 to 106 for all other bacteria. The media used in these measurements were Eugon blood agar for streptococci, chocolate agar for Neisseria, Arakawa agar for corynebacteria, GAM agar for anaerobes, PPLO agar for Mycoplasma, and heart infusion agar for all other bacteria. All plates were incubated overnight at 37°C in air, with the exception of the anaerobes, which were incubated in a GasPak jar (BBL Microbiology Systems), H. influenzae and Neisseria, which were incubated in a 5% CO2 incubator for 48 h, and Mycoplasma, which was incubated in moisture-saturated box for...

A sensitive and reliable high-pressure liquid chromatography (HPLC) assay for miloxacin and its two principal metabolites, 5,8-dihydro-8-oxo-2H-1,3-dioxolo[4,5-g]quioline-7-carboxylic acid (M-1) and 1,4-dihydro-1,6-dimethoxy-7-hydroxy-4-oxoquinoline-3-carboxylic acid (M-2), in human serum and urine was developed. A strong anion-exchange Zipax SAX column using a mobile phase of 0.01 M citric acid solution containing 0.03 M sodium nitrate with pH 5.0 was used to achieve separation of the three compounds. The retention times of miloxacin, M-1, and M-2 were 3.8, 9.3, and 5.9 min, respectively. Serum and urine concentrations of these compounds as low as 10 ng/ml were measured. When results from the HPLC assay were compared with those from the microbiological assay of serum and urine samples from human subjects receiving miloxacin orally, the correlation coefficients were 0.94 for the serum and 0.99 for the urine. The HPLC assay method presents an alternative to the microbiological assay and permits future pharmacokinetic investigations of miloxacin.Miloxacin, 5,8-dihydro-5-methoxy-8-oxo-2H-1,3-dioxolo[4,5-g]-quinoline-7-carboxylic acid, is an antimicrobial agent which has been synthesized and tested for antimicrobial activities in our laboratories (1, 2). It has a wide spectrum of activity against both gram-negative and -positive bacteria (1, 2). Clinical trials, especially for the evaluation of the drug in urinary tract infections, are under way (4).Studies in animals have shown that miloxacin is transformed to several metabolites mainly by the liver (5-8). The metabolites identified in these studies are 5,8-dihydro-8-oxo-2H-1,3-dioxolo[4,5-g]-quinoline-7-carboxylic acid (M-1), 1,4-dihydro-1,6-dimethoxy-7-hydroxy-4-oxoquinoline-3-carboxylic acid (M-2), and 1,4-dihydro-6,7-dihydroxy-4-oxoquinoline-3-carboxylic acid (M-3) and their glucuronides. In vitro human samples. Standard solutions of miloxacin, M-1, M-2, and M-3 in 1% aqueous sodium carbonate solution were prepared freshly each week and stored in the dark at 4°C between use. A quantity of 0.1 ml of each of the standards was added to 2 ml of human serum or urine which was collected from nonmedicated healthy volunteers, and this mixture was incubated at room temperature for at least 20 min. Blanks were prepared in the same manner except for omission of the standard materials.In vivo human samples. Serum and urine samples were obtained from healthy volunteers receiving 500 mg of miloxacin orally after the morning meal. Serum samples were collected at 1, 2, 3, 4, and 6 h after administration; urine samples were collected at 0 to 2, 2 to 4, 4 to 6, and 6 to 8 h. Samples were stored at -20°C for as long as 1 month before analysis. The stability of miloxacin under these conditions was confirmed in the animal studies with ['4C-]