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Embryotoxicity studies of norfloxacin in cynomolgus monkeys: I. Teratology studies and norfloxacin plasma concentration in pregnant and nonpregnant monkeys.

Norfloxacin, a new orally active antibiotic, was investigated in cynomolgus monkeys for potential developmental toxicity. Fifty-seven monkeys were administered a control vehicle or norfloxacin by nasogastric gavage during the major period of organogenesis on gestational days (GD) 21 through 50 at doses of 0, 50, 100, 150, or 200/300 mg/kg/day. There was no evidence of teratogenicity at any dose level. Maternotoxicity and a significant increase in embryolethality occurred following doses of 200/300 mg/kg/day. The maternotoxicity was not expected based on range-finding studies in nonpregnant female monkeys, which showed no signs of toxicity in doses up to 500 mg/kg/day. Additional studies were conducted to determine if norfloxacin caused similar toxicity later in gestation. Forty-six pregnant monkeys were dosed with a control vehicle or 200 mg/kg/day norfloxacin for one of three 10-day periods on GD 36-45, 71-80, or 111-120. There were no maternotoxic, embryotoxic, or fetotoxic effects observed. Plasma concentrations of norfloxacin in five cynomolgus monkeys following 50 and 200 mg/kg oral doses were not dose-proportionate. However, at a given dose, administered in cross-over fashion, plasma concentrations of norfloxacin were higher in nonpregnant females (approximately 20-40%) than during pregnancy when the same subject was compared. At the no-observed-effect dose for maternal and embryotoxicity (50 mg/kg), peak plasma concentrations of norfloxacin in pregnant cynomolgus monkeys are approximately threefold higher than those observed in human volunteers receiving norfloxacin at the maximum recommended therapeutic dose of 400 mg (5.7 mg/kg based on 70 kg body weight) twice per day.

Animals↗

Topically administered norfloxacin compared with topically administered gentamicin for the treatment of external ocular bacterial infections. The Worldwide Norfloxacin Ophthalmic Study Group.

In this double-masked study, we randomly assigned 488 patients with clinical signs of acute bacterial conjunctivitis or blepharitis, or both, to treatment with either norfloxacin ophthalmic solution 0.3% (245) or gentamicin ophthalmic solution 0.3% (243) for one week. Of the patients with positive cultures, 71% (85 of 120) of the norfloxacin-treated patients and 65% (86 of 133) of the gentamicin-treated patients were clinically cured. An additional 25% (30 of 120) of norfloxacin-treated patients and 32% (43 of 133) of gentamicin-treated patients were clinically improved. On the basis of posttreatment cultures, 89% of all cultured bacteria were eradicated (146 of 179 organisms) or suppressed (14 of 179 organisms) after treatment with norfloxacin. The condition of five norfloxacin-treated patients did not clinically improve, compared with the condition of eight gentamicin-treated patients. Both antibiotics had similar efficacy against gram-positive and against gram-negative organisms. One norfloxacin-treated patient and two gentamicin-treated patients withdrew from the study because of local intolerance. Norfloxacin appears to be an effective and relatively safe agent for the treatment of bacterial infections of the eyelids or conjunctiva, or both. In this study, norfloxacin was clinically and microbiologically similar in activity to gentamicin.

Administration, Topical↗

The safety and efficacy of topical norfloxacin compared with chloramphenicol for the treatment of external ocular bacterial infections. The Norfloxacin-Chloramphenicol Ophthalmic Study Group.

Two hundred and forty-six patients with signs of acute bacterial conjunctivitis and/or blepharitis were randomised to receive either norfloxacin or chloramphenicol for one week in this double-masked parallel group study. Ninety-two per cent of the norfloxacin-treated patients and 93% of the chloramphenicol-treated patients were rated as either clinically improved or cured at the end of the treatment period. Based upon pre-treatment bacteriological cultures, 31.3% of the patients had significant bacterial infection of the lids and/or conjunctiva. All of these culture-positive patients were rated as either clinically improved or cured. Based upon post-treatment cultures, 72 of 82 strains of Gram-positive and Gram-negative bacteria were eradicated or suppressed following treatment with either norfloxacin or chloramphenicol. However six of 41 strains persisted for norfloxacin and four of 41 for chloramphenicol. Two norfloxacin-treated patients and three chloramphenicol-treated patients had adverse experiences, predominantly ocular discomfort, which required cessation of drug therapy. Norfloxacin appears to be an effective and relatively safe agent for the treatment of bacterial infections of the lids and/or conjunctiva. In this study, norfloxacin was clinically and microbiologically similar in activity to chloramphenicol.

Acute Disease↗

Norfloxacin and silver-norfloxacin as topical antimicrobial agents: results of in vitro susceptibility testing against bacteria and Candida sp isolated from burn patients.

Because of its broad spectrum of antibacterial action, Norfloxacin, a new quinoline carboxylic acid compound, was formulated in a topical cream base and tested for activity against a variety of bacteria and yeasts isolated from burn patients. An in vitro agar well diffusion topical susceptibility test was used. The silver salt of Norfloxacin also was tested. For comparative purposes, commonly used topical antibacterial and antifungal preparations were examined as well. No bacterial isolate tested was resistant to the action of Norfloxacin or that of silver-Norfloxacin. Furthermore, all Candida organisms assayed were susceptible to silver-Norfloxacin. All other topical agents tested had some strains of bacteria or yeast, or both, that were resistant to their action. Therefore, Norfloxacin and, particularly, silver-Norfloxacin, warrant further development as topical anti-infective agents for use in treating burn patients.

Anti-Infective Agents↗

Efficacy and safety of norfloxacin 800 mg once-daily versus norfloxacin 400 mg twice-daily in the treatment of uncomplicated urinary tract infections in women: a double-blind, randomized clinical trial.

Norfloxacin 400 mg twice-a-day has proven to be effective and safe in the treatment of uncomplicated urinary tract infections (UTI). Since previous pharmacokinetic studies demonstrate the feasibility of using norfloxacin 800 mg once-daily, and this scheme is assumed to improve patient compliance, a double-blind randomized clinical trial was performed to compare the efficacy and safety of norfloxacin 800 mg once-daily (Group A) versus norfloxacin 400 mg twice-daily (Group B) in the treatment of adult female UTI for a 7-10 day period. Eighty-six adult women with clinical symptoms and urinary sediment signs suggestive of UTI were enrolled. In Group A, treatment was clinically assessed as effective in 95.3% and bacteriologically effective in 92.0% of the patients. In Group B, clinical and bacteriological efficacy was 100% and 95.5%, respectively. Differences between groups are not statistically significant. Adverse events were reported by 14.0% of patients in Group A and 9.6% in Group B (difference not statistically significant). There was one withdrawal due to dizziness. In this study, norfloxacin 800 mg once-a-day was as effective and safe as norfloxacin 400 mg twice-a-day in the treatment of uncomplicated urinary tract infections in women.

Adolescent↗

Norfloxacin and silver norfloxacin in the treatment of Pseudomonas corneal ulcer in the rabbit.

Norfloxacin is a new synthetic antibiotic with a broad spectrum of activity against gram-positive and gram-negative bacteria, and is more effective than the aminoglycosides against P aeruginosa. In this study norfloxacin was particularly effective in treatment of P aeruginosa infection of the rabbit cornea, and caused no toxicity in normal rabbit eyes after prolonged administration. The addition of silver to norfloxacin enhances its antipseudomonal activity, and broadens its spectrum to include antifungal activity. In this study, silver norfloxacin appears to be the most effective antibiotic against P aeruginosa corneal ulcer in the rabbit. Because of its broad antibacterial spectrum, silver norfloxacin may be useful in the initial treatment of bacterial corneal ulcer before the identity of the bacteria is known. Because of its low toxicity in topical administration, and its antifungal and antibacterial activity, silver norfloxacin may be helpful in prophylaxis against infection in chronic corneal ulcers.

Aminoglycosides↗

Antimicrobial activity of norfloxacin in enteric and urinary tract infections: combined effect of norfloxacin with aminoglycosides, tetracycline and chloramphenicol.

A comparative study of the in vitro activity of norfloxacin was performed versus that of aminoglycosides, pipemidic acid, tetracycline and chloramphenicol. These antibiotics are the most commonly used antimicrobial agents in the treatment of enteric and urinary tract infections. Results obtained with norfloxacin against Gram-negative isolates tested were very encouraging. MIC values for the Enterobacteriaceae were less than or equal to 0.47 mcg/ml, and for Pseudomonas and Acinetobacter less than or equal to 32.5 mcg/ml. The activity of norfloxacin against Pseudomonas was inferior to that of amikacin, but superior to that of gentamicin. In association with aminoglycosides, norfloxacin proved to be most useful in the treatment of urinary tract infections, while norfloxacin associated with tetracycline and chloramphenicol did not give satisfactory results in the treatment of enteric infections.

Acinetobacter↗

The safety and efficacy of topical norfloxacin compared with placebo in the treatment of acute, bacterial conjunctivitis. The Norfloxacin-Placebo Ocular Study Group.

Two hundred and eighty-four patients with acute conjunctivitis were enrolled in a double-masked study comparing norfloxacin ophthalmic solution with placebo. The proportion of patients who were clinically improved after 5 days treatment was 88.1% in the norfloxacin group and 71.6% in the placebo group (p less than 0.01). The proportion of patients who had all organisms eradicated, including the coagulase-negative staphylococci, after two to three days treatment was 52.7% for norfloxacin and 23.9% for placebo (p less than 0.01) and 64.7% and 26.3% (p less than 0.01) respectively when the coagulase-negative staphylococci were not included. Adverse experiences occurred in 4.2% of the patients receiving norfloxacin compared to 7.1% of the placebo patients. None of the adverse experiences was serious.

Acute Disease↗

[Determination of norfloxacin, an active dissociation product of silver norfloxacin, in guinea pig plasma and tissue by high performance liquid chromatography with column-switching].

A column switching HPLC method was established for the determination of norfloxacin, and active dissociation product of silver norfloxacin, in guinea pig plasma and tissues. The pre-treating column (50 mm x 5 mm ID) and analytical column (150 mm x 5 mm ID) were packed with mu-Bondapak C18, 37-50 microns and YWG-C18, 10 microns, respectively. A mixture of CH3OH-0.008 mol/L phosphate buffer-0.05 mol/L tetrabutylammoniun bromide (25:75:4) was used as the analytical mobile phase with a flow rate of 1 ml/min. The pre-treating mobile phase was 0.008 mol/L phosphate buffer with a flow rate of 3 ml/min. UV detection was made at 280 nm. The results were linear within a range of 2-128 micrograms/ml norfloxacin for plasma. The lowest detection limit was 0.25 microgram/ml for plasma. The mean recovery of the method was 102% with a relative standard deviation of less than 7%.

Administration, Topical↗

Double-blind, randomized comparison of 24 weeks of norfloxacin and 12 weeks of norfloxacin followed by 12 weeks of placebo in the therapy of complicated urinary tract infection.

We evaluated the benefits of prolonging norfloxacin therapy from 12 to 24 weeks for complicated urinary tract infection in a double-blind, randomized, placebo-controlled study. During the second 12 weeks, norfloxacin was superior to placebo (P less than 0.05) in suppressing bacteriuria. Adverse effects were common but mostly confined to the initial 12 weeks.

Bacteriuria↗

Validation of a high-performance liquid chromatographic method for the determination of norfloxacin and its application to stability studies (photo-stability study of norfloxacin).

The development and validation study of a sensitive, rapid, reproducible, easy and precise reversed-phase high-performance liquid chromatographic assay for norfloxacin (NFLX) samples from photo-stability of solid dosage forms, without using gradient elution, extraction methods and without using counter-ion has been carried out. The method showed excellent linearity (r2> or =0.999) in the range 1-20 microg ml(-1) using a Lichrosorb-RP-8 column (10 microm, 20 cm x 4.6 mm) and UV-detection (278 nm) at ambient temperature. This method showed good efficiency for the analysis of photodegraded NFLX samples, and was applied to study the photo-stability of NFLX tablets under different conditions (direct sun light, ultraviolet light and fluorescent light). It was proven that the use of a disintegrant can increase the photo-stability of the NFLX in the tablets. This effect was studied in directly compressible tablets with microcrystalline cellulose (MCC) and mannitol for direct compression.

Anti-Infective Agents↗

The effect of photodegradation on the fluorescent properties of norfloxacin: (photodegradation and fluorescence of norfloxacin).

Norfloxacin (NFLX), a broad spectrum antibacterial quinolone, is a very thermostable but photosensitive drug, especially in solution leading to the formation of an ethylenediamine degradate. The modification of the fluorescent properties of NFLX in acid solution after exposure to fluorescent light and the degradation mechanisms were studied. Two analytical methods were previously developed and validated for NFLX, ultraviolet spectrophotometry (UV) and spectrofluorimetry (FL). Data obtained using both methods in the analysis of remaining NFLX in terms of percent recoveries revealed that there was no statistically significant modifications of the UV signal and of the recoveries obtained by the method. However, an important increase of the fluorescent signal after light exposure of NFLX solutions appeared, which led to an increase of the average recovery up to 270% over 15 months. Using a previously validated HPLC method for the photostability studies of NFLX, a loss of 5% with respect to the initial drug amount was observed. The study of UV and fluorescence spectra evidenced the formation of the degradation product, which induced significant modification of the fluorescent properties of NFLX samples. These results clearly indicated that FL analysis definitively is the method of choice and can be used to study the photodegradation of NFLX.

Anti-Infective Agents↗

[Evaluation of norfloxacin in the pediatric field. Pediatric Study Group for Norfloxacin].

Norfloxacin (NFLX, AM-715), a new quinolone antibiotic agent, was evaluated clinically and bacteriologically for its efficacy and safety in pediatrics by a study group organized with pediatricians from all over the country. A summary of the results of the evaluation is as follows. 1. Incidence of NFLX-resistant strains (MIC over 12.5 micrograms/ml) isolated from children with various infections was 1.6% (8/512). One resistant strain was observed among 45 isolates of Staphylococcus aureus, and none among 30 isolates of Pseudomonas aeruginosa. 2. After single oral administration of 1.5-2.9, 3.0-4.8 and 5.1-6.1 mg/kg NFLX in tablet form at fasting, mean peak values of serum concentration of 0.37, 0.56, 0.92 micrograms/ml, T1/2 of 2.5, 2.6, 2.6 hours and urinary recovery rates in 8 hours at 25.3, 25.3, 27.1% were observed, respectively. 3. Clinical effects were studied chiefly in intestinal and urinary tract infections. Among 317 patients from whom pathogens had been isolated, responses to the treatment were excellent in 187, good in 79, fair in 9, poor in 7, and unknown in 35 cases. The overall efficacy rate was 94.3% (266/282) and the efficacy rate for excellent responses was 70.3% (187/266). Among all the 406 patients treated, including those with undetermined pathogens, responses were excellent in 233, good in 106, fair in 11, poor in 11, and unknown in 45 cases. The overall efficacy rate was 93.9% (339/361). 4. Clinical effects of NFLX classified by diseases with identified pathogens were 81.8% (9/11) for acute pneumonia, 80.8% (21/26) for other respiratory infections, 95.8% (23/24) for bacillary dysentery, 98.6% (70/71) for Campylobacter enteritis, 100% (24/24) for Salmonella enteritis, 100% (6/6) for other acute enteritis and 98.1% (104/106) for urinary tract infections. Including other infections as high as 94.3% (266/282) of efficacy rate was obtained in total. There was no significant difference in NFLX efficacies between unidentified and identified pathogens. Thus, the total clinical efficacy rate was 93.9% (339/361). 5. The total eradication rate of 325 pathogens evaluable was 84.3%, with identical eradication rates for Gram-positive cocci (GPC) (43/51) and for Gram-negative rods (GNR) (231/274). 6. The optimal daily dose of NFLX seemed to be in a range between 6.0 and 12.0 mg/kg, and the optimal duration of treatment to be 7 days for children over 5 years old. 7. The clinical efficacy in treating P. aeruginosa infections in 12 patients was 100% (11/11) and the eradication rate was 83.3% (10/12).(ABSTRACT TRUNCATED AT 400 WORDS)

Administration, Oral↗

Sucralfate reduces the gastrointestinal absorption of norfloxacin.

The effect of sucralfate on the bioavailability of norfloxacin after single 400-mg doses of norfloxacin was evaluated in eight healthy males. Subjects received each of the following treatments in random sequence: (i), norfloxacin, 400 mg alone; (ii) sucralfate, 1 g, concurrently with norfloxacin, 400 mg; and (iii) sucralfate, 1 g, followed by norfloxacin, 400 mg, 2 h later. One day before administration of treatments 2 and 3, 1 g of sucralfate was given at 7 a.m., 11 a.m., 5 p.m., and 10 p.m. Blood samples were collected immediately before the norfloxacin dose and at 0.25, 0.5, 0.75, 1.0, 1.5, 2, 3, 4, 6, 8, 12, and 24 h postdose. Urine was collected in divided intervals: from 0 to 12, from 12 to 24, and from 24 to 48 h. Norfloxacin concentrations in plasma and urine were determined by high-performance liquid chromatography. Mean area under the plasma concentration-versus-time curve extrapolated to infinity decreased significantly (P less than 0.001) after norfloxacin was given with and 2 h after sucralfate. The relative bioavailabilities were 1.8% when norfloxacin was taken with sucralfate and 56.6% when it was taken 2 h after sucralfate. After norfloxacin was given alone, the mean norfloxacin concentrations in urine collected during intervals of 0 to 12, 12 to 24, and 24 to 28 h were 118.9 +/- 72.3, 18.8 +/- 12.5, and 2.4 +/- 2.2 micrograms/ml, respectively. After norfloxacin was given with sucralfate, however, the mean norfloxacin concentrations in urine collected during the same time intervals were 6.8 +/- 4.7, 1.8 +/- 1.4, and 0 +/- 0 microgram/ml, respectively. Because of low pH and relatively high magnesium concentration in urine, susceptibilities of bacteria in urine are 8- to 32-fold lower than in broth. This fact, in combination with the reduced bioavailability of norfloxacin in the presence of sucralfate or antacids, is likely to result in treatment failure. The effect of sucralfate given after norfloxacin was not examined, nor was the effect of sucralfate given more than 2 h before norfloxacin. Administration or norfloxacin with sucralfate should therefore by avoided.

Administration, Oral↗

Inhibition of norfloxacin absorption by antacids.

The effect of antacids on the systemic absorption of oral norfloxacin was evaluated in 12 healthy volunteers. Subjects were given each treatment in a balanced sequence at 7-day intervals. Treatments included 400 mg of norfloxacin alone, 400 mg of norfloxacin 5 min after aluminum-magnesium hydroxide (Maalox), Maalox 2 h after 400 mg of norfloxacin, and 400 mg of norfloxacin 5 min after calcium carbonate (Titralac). Blood and urine samples were collected at predetermined time intervals for 24 and 48 h, respectively. Norfloxacin concentrations in plasma and urine were determined by high-pressure liquid chromatography. The area under the plasma concentration-versus-time curve from time zero to infinity and urinary recovery were used to compare the relative bioavailability of norfloxacin with antacids with that of norfloxacin alone. Norfloxacin bioavailability was markedly reduced when subjects received antacid pretreatment. When norfloxacin was given 5 min after Maalox and Titralac, the bioavailabilities were 9.02 and 37.5%, respectively, relative to that for 400 mg of norfloxacin alone. When Maalox was given 2 h after norfloxacin, maximal concentrations of norfloxacin in plasma occurred between 1 and 1.5 h postdose, and absorption was reduced to a lesser extent, with a relative bioavailability of 81.31%. Norfloxacin concentrations in urine were also reduced as a result of antacid administration. Antacids containing aluminum and magnesium salts and calcium carbonate should be avoided by patients taking norfloxacin.

Absorption↗