The comparative activity of norfloxacin with other antimicrobial agents against Gram-positive and Gram-negative bacteria

Parenteral ofloxacin in treatment of pyelonephritis

The interim findings of two studies of intravenous ofloxacin for the treatment of pyelonephritis are presented. The findings are from one center of a multicenter trial. In the first study intravenous (IV) ofloxacin was given to 34 patients with urine-culture-positive pyelonephritis. After three days of intravenous therapy patients could be switched to oral ofloxacin. Microbiologic eradication occurred in 97 percent and clinical cures in 97 percent of the patients treated with ofloxacin. There were three probable drug-related adverse events. In the second comparative study 38 patients with pyelonephritis were randomized to receive IV ofloxacin with the option of switching to oral ofloxacin after three days. IV ceftazidime was given to 30 patients with pyelonephritis with the option of switching to trimethoprim/sulfamethoxazole (TMP/SMX) after three days. Microbiologic cures were experienced by 97 percent of the ofloxacin patients and by 100 percent of the ceftazidime patients. Probable drug-related adverse reactions were experienced by 3/28 ofloxacin patients and by none of the ceftazidime patients. These interim study findings indicate that the intravenous preparation of ofloxacin is efficacious in the treatment of pyelonephritis and that it is safe. In addition, IV ofloxacin is as efficacious as IV ceftazidime for the treatment of pyelonephritis.

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.

Norfloxacin: clinical pharmacology and clinical use

Norfloxacin, a nalidixic acid analog, is the first of the fluorinated quinolinecarboxylic acids to be marketed in the United States. It demonstrates potent antibacterial activity against aerobic, gram-negative bacteria including the Enterobacteriaceae, gentamicin-resistant Pseudomonas aeruginosa, and penicillin-resistant Neisseria gonorrhoeae. Norfloxacin exhibits good activity against methicillin-resistant and -sensitive Staphylococcus aureus, but less activity against most other aerobic, gram-positive organisms. Anaerobic bacteria are resistant to the drug. Resistance to norfloxacin is not plasmid mediated, but is secondary to bacterial mutation, and occurs less frequently than nalidixic acid resistance. Its pharmacokinetic properties after a 400-mg oral dose consist of a peak serum concentration of 1.3-1.58 micrograms/ml, an elimination half-life of 3-7 hours, and good penetration into kidney and prostatic tissues. Renal excretion is the major route of elimination. Norfloxacin is highly effective in the treatment of uncomplicated and complicated urinary tract infections, and gonococcal urethritis. Adverse effects are generally well tolerated and usually do not require discontinuation of therapy.

Norfloxacin, a fluoroquinolone antibacterial agent. Classification, mechanism of action, and in vitro activity

Norfloxacin is an orally absorbed fluoroquinolone antibacterial with a fluorine at position 6 and a piperazine ring at position 7. These changes have resulted in a marked enhancement (compared with that of the older quinolones) of in vitro antibacterial activity. Specifically, the antibacterial spectrum of norfloxacin includes Pseudomonas aeruginosa, as well as enteric pathogens. Norfloxacin is also active against both penicillin-susceptible and penicillin-resistant strains of Neisseria gonorrhoeae. Relative to its activity against gram-negative bacteria, norfloxacin is somewhat less active against gram-positive cocci. In general, the staphylococci are more susceptible to the drug than are the streptococci. As with all fluoroquinolones, norfloxacin's activity against anaerobic bacteria is poor. For urinary tract bacterial isolates, the following Bauer-Kirby disk diffusion zone-size breakpoints have been proposed: greater than or equal to 17 mm, susceptible; 13 to 16 mm, intermediate; less than or equal to 12 mm, resistant. Bacteria with minimal inhibitory concentrations (MICs) less than or equal to 16 micrograms/ml are considered susceptible; those with MICs greater than or equal to 32 micrograms/ml are considered resistant to norfloxacin. The mechanism of action of norfloxacin involves inhibition of the A subunit of the important bacterial enzyme DNA gyrase, which is essential for DNA replication. Plasmid-mediated resistance to the fluoroquinolones is not encountered. Further, although some cross-resistance within the fluoroquinolone class has occurred, there is little cross-resistance between norfloxacin and antibiotics of other classes.

Comparison of norfloxacin and nalidixic acid for treatment of dysentery caused by Shigella dysenteriae type 1 in adults

A severe epidemic of dysentery began late in 1979 in northeast Zaire and spread to Rwanda, Burundi, and Tanzania. The epidemic strain is a multiply resistant Shigella dysenteriae type 1, which acquired resistance against trimethoprim and more recently against nalidixic acid in the course of the epidemic. A comparative open trial in Rwandan adults with Shiga dysentery involved 18 patients treated with norfloxacin at 400 mg twice daily and 12 patients treated with nalidixic acid at 1 g three times daily for 5 days. All isolates showed in vitro susceptibility to both drugs. Though norfloxacin eliminated Shigella organisms from stools more rapidly than nalidixic acid, its clinical superiority did not reach the level of significance. Norfloxacin is a promising drug and is more effective than nalidixic acid in the treatment of multiresistant shigellosis.

Norfloxacin: a quinoline antibiotic

Norfloxacin is a quinoline (quinolinecarboxylic acid) that should prove successful in treating infections that currently require hospitalization and intravenous antibiotics. Although a nalidixic acid derivative, it possesses greater antibacterial activity against gram-positive and gram-negative bacteria. Compared with other antimicrobial agents, norfloxacin is more potent than the aminoglycosides, first-, second-, and third-generation cephalosporins, tetracycline, trimethoprim-sulfamethoxazole, carbenicillin, piperacillin, nalidixic acid, oxolinic acid, cinoxacin, and enoxacin. In the clinical studies to date, the side effects of norfloxacin have been minimal, but include nausea, vomiting, anorexia, dizziness, headache, drowsiness, depression, and a bitter taste in the mouth. In studies with more than 4000 patients, the incidence of side effects ranged from 3.9 to 4.7 percent, with most appearing by the second day of therapy.

Comparative in vitro activity of three new quinolone antibiotics against recent clinical isolates

New orally absorbable quinolone derivatives, ciprofloxacin, norfloxacin, and ofloxacin demonstrated excellent activity in vitro against clinical isolates of Escherichia coli, Klebsiella, Enterobacter, Proteus mirabilis, Proteus sp. indole-positive, Pseudomonas aeruginosa, Serratia marcescens, Staphylococcus aureus, Streptococcus pyogenes and enterococci. None of the 3 drugs was more than moderately effective against Bacteroides fragilis. Ciprofloxacin was 2-4 times more effective against most gram-negative strains than was either norfloxacin or ofloxacin, and was also the most effective against gram-positive strains, though the difference was less marked. Ciprofloxacin and ofloxacin were almost equally effective against S. aureus. Results with agar and with broth were comparable. The activities of all 3 drugs were essentially independent of inoculum size, as the MIC values increased less than one dilution step when the inoculum was increased from 10(3) to 10(6). The new quinolone derivatives would appear to be promising alternatives to injectable drugs such as the aminoglycosides and cephalosporins.

Comparative in vitro activity of norfloxacin and seven other antimicrobial agents against clinical isolates from urinary tract infections

The in vitro activity of norfloxacin, a new quinolone derivative, was tested against 469 clinical isolates derived mainly from urinary samples from outpatients. It inhibited all Escherichia coli, Klebsiella oxytoca and Proteus strains at a concentration of 0.25 micrograms/ml, and all Pseudomonas aeruginosa, Enterobacter, Klebsiella pneumoniae, Staphylococcus and Enterococcus strains at a concentration of 8 micrograms/ml or less. Norfloxacin proved to be more effective than nalidixic acid, trimethoprim, mecillinam and nitrofurantoin against all gram-negative rods tested.

In vitro antibacterial activity of three new quinolone derivatives: rosoxacin, norfloxacin, pefloxacin

The in vitro activities of rosoxacin, norfloxacin and pefloxacin against 480 bacterial strains were studied. MIC90s of norfloxacin and pefloxacin were less than or equal to 2 micrograms/ml for E. coli, Klebsiella sp., E. cloacae, Proteus sp. and Staphylococcus sp., less than or equal to 8 micrograms/ml for C. freundii, Providencia sp., S. faecalis, and non fermentative Gram-negative bacteria, while they were of 32 micrograms/ml for S. marcescens. Rosoxacin exhibited a lower activity with MIC90s 2 to 16 fold higher against Enterobacteriaceae and P. aeruginosa. Ninety per cent of isolates resistant to nalidixic-acid appeared susceptible to norfloxacin and pefloxacin with MIC less than or equal to 16 micrograms/ml.

A laboratory assessment of ciprofloxacin and comparable antimicrobial agents

The in vitro activity of ciprofloxacin against a wide range of bacterial isolates was assessed in comparison with norfloxacin, enoxacin, co-trimoxazole and penicillin (or ampicillin) where appropriate. Minimal inhibitory concentrations (MICs) indicated that ciprofloxacin was highly active against gram-negative bacilli of the Enterobacteriaceae and Pseudomonas groups, notably against strains resistant to gentamicin. Similarly, Staphylococcus aureus (including methicillin-resistant strains) and Haemophilus influenzae were susceptible, regardless of penicillinase production. Norfloxacin and enoxacin were less active than ciprofloxacin against the majority of species tested, although enoxacin blood levels were generally higher. Most co-trimoxazole-resistant strains were susceptible to the quinoline group of drugs.