BMY 28100, a new oral cephalosporin

An LC-MS/MS method for simultaneous determination of cefprozil diastereomers in human plasma and its application for the bioequivalence study of two cefprozil tablets in healthy Chinese volunteers

A rapid and sensitive liquid chromatography-tandem mass spectrometric method was developed for the first time and validated for the determination of cefprozil diastereomers in human plasma. The plasma samples were prepared by protein precipitation using acetonitrile. Detection was performed using an electronic spray ion source in the negative ion mode, operating in the multiple reaction monitoring of the transitions m/z 388.0 to m/z 205.0 for cefprozil diastereomers and m/z 346.1 to m/z 268.1 for cephalexin (the internal standard). The calibration curves of cis-cefprozil and trans-cefprozil were linear in the ranges 0.125-16.0 µg/mL and 0.0403-1.72 µg/mL, respectively. The lower limits of quantification of cis- and trans-cefprozil were 0.125 and 0.0403 µg/mL in human plasma, respectively. The intra- and inter-day precisions of cis- and trans-cefprozil were all <9.7%, and the accuracy ranged from 99.2 to 104.7% and from 100.6 to 102.2%, respectively. The validated method was successfully applied to a bioequivalence study of two cefprozil formulations in 24 healthy Chinese volunteers. The two cefprozil tablets were bioequivalent by measurement of cis-, trans- and total cefprozil. We suggest that the bioequivalence of cefprozil formulations can be evaluated only using cis-cefprozil as the analyte in future studies.

HPLC method for simultaneous determination of cefprozil diastereomers in human plasma

A high-performance liquid chromatography method was developed for the determination of cefprozil diastereomers in human plasma. Cefprozil exists as cis and trans isomer at the ratio of 90:10. Plasma samples were prepared by protein precipitation using acetonitrile, trichloroacetic acid and methylene chloride. After the mixtures were vortexed and centrifuged, the aqueous supernatant was injected into a reversed-phase C8 column. The mobile phase consisted of acetonitrile, glacial acetic acid and distilled water at the volume ratio of 5.5:1.75:92.75 (pH 2.7). The signals were monitored with UV detection at 280 nm. The calibration curves of cis and trans isomer were linear in concentration ranges of 0.1-25 and 0.02-2.5 microg/mL with the correlation coefficient of 0.9999 and 0.9989, respectively. After oral administration of cefprozil in humans, Cmax and Tmax of total cefprozil were 18.80 +/- 2.14 microg/mL and 2.06 +/- 0.62 h. This method was sensitive with excellent selectivity and reproducibility, and successfully applied to a bioavailability study of cefprozil in healthy subjects.

Cefaclor: a contemporary look at susceptibility of key pathogens from around the globe

The orally administered cephalosporin antibiotic, cefaclor, has been available for clinical use in many countries since 1979. Because widespread antibiotic use is often cited as a factor in the emergence of bacterial resistance to antibiotics, we sought to determine the degrees of resistance to cefaclor expressed by key pathogens recently isolated in 10 countries widely distributed around the world. Using the E-test, minimal inhibitory concentrations (MIC) were determined for cefaclor and several comparator antibiotics against approximately 700 fresh clinical isolates of each of six bacterial species. The results demonstrated that > 90% of Haemophilus influenzae (beta-lactamase producing and non-producing), Haemophilus parainfluenzae (beta-lactamase producing and non-producing), Moraxella catarrhalis (> 90% beta-lactamase producing), and methicillin-susceptible Staphylococcus aureus, and 85% of Escherichia coli were susceptible to cefaclor at the NCCLS interpretive breakpoints. MIC distributions showed that there has been no change in the activity of cefaclor against penicillin-susceptible strains of Streptococcus pneumoniae since 1977.

Comparative efficacy and safety of cefprozil versus penicillin, cefaclor and erythromycin in the treatment of streptococcal pharyngitis and tonsillitis

Cefprozil is a new oral cephalosporin with an enhanced in vitro spectrum of activity that includes group A beta-hemolytic streptococci (GABHS). Four multicenter randomized clinical trials were conducted to compare the clinical efficacy and safety of cefprozil administered once or twice a day for the treatment of mild to moderate GABHS tonsillitis and pharyngitis. A total of 1597 patients were enrolled in the trials. Patient demographics and severity of infection were similar for all treatment groups. In Study 1, cefprozil administered at 20 mg/kg once daily was clinically, in 68 of 76 patients (89%) and bacteriologically, in 66 of 74 patients (89%) superior to penicillin -51 of 69 (74%) and 46 of 69 (67%)--administered three times a day in patients of two to 12 years of age. In Study 2, the patients enrolled were 13 years of age and older, and cefprozil administered at 20 mg/kg once a day had similar clinical (93% vs. 90%) and bacteriological (95% vs. 94%) response rates as cefaclor administered three times a day. Study 3 demonstrated that cefprozil administered twice daily was similar to penicillin given three times a day, the clinical satisfactory response being 164 of 175 (94%) for cefprozil and 146 of 165 (88%) for penicillin. In Study 4, identical clinical and bacteriologic responses (95%) were observed for cefprozil administered once a day and erythromycin ethylsuccinate administered four times a day in children over two years of age. There were no significant differences in the incidence or severity of drug-related adverse events, which, when reported, were mild and transient.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative microbiological activity and pharmacokinetics of cefprozil

In vitro studies on the activity of cefprozil have been conducted in Europe and North America. Against gram-negative bacilli, cefprozil and cefaclor are at least two to four times more active than cephalexin. Cefixime is more active against these organisms. Against gram-positive cocci, cefprozil is at least two to four times more active than cefaclor and cephalexin; cefixime has limited gram-positive activity, and is particularly inactive against staphylococci (MIC90 32 mg/l). Cefprozil is highly active against Streptococcus pneumoniae (unlike cefixime). Those strains of this genus that display intermediate resistance to pneumococci are more susceptible to cefprozil than cefaclor. Neisseria species and Moraxella catarrhalis are susceptible to cefprozil (MIC90 0.06 and 1 mg/l). beta-lactamase-producing strains of Haemophilus influenzae appear to be susceptible to cefprozil, as the reported MIC90 is 2-4 mg/l. Enterococci, Pseudomonas aeruginosa, and those strains of the Enterobacteriaceae that commonly possess a chromosomal cephalosporinase (e.g., Providencia, Morganella and Enterobacter) are generally considered to be resistant to cefprozil as well as to other oral cephalosporins. Cefprozil appears to display enhanced stability to the commonly encountered Tem-1 and SHV-1 plasmid-mediated beta-lactamases, as found in Haemophilus influenzae, Neisseria gonorrhoeae and the Enterobacteriaceae. Cefprozil is rapidly absorbed, reaching a maximum concentration 0.9 to 1.2 h post-dose. Following oral doses of 250 and 500 mg, the Cmax is 6.2 and 10.0 mg/l respectively. Serum half-lives are generally reported as between 1.2 and 1.4 h, and urine recovery is high, 57-70%.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy and safety of cefprozil versus other beta-lactam antibiotics in the treatment of lower respiratory tract infections

Cefprozil was evaluated in four multicentre comparative studies in the treatment of acute respiratory tract infections. In two studies, cefprozil 500 mg q. 12 hours was compared to cefaclor 500 mg q. eight hours for ten days of therapy. Randomization was on a 2:1 (cefprozil:cefaclor) basis in the European centres and 1:1 in North America. The clinical efficacy in acute bronchitis was 88% (284 out of 324 patients) for cefprozil and 88% (183 out of 208) for cefaclor, with successful bacteriological eradication of the causative pathogen in 86% and 82% of the patients, respectively. Amongst the patients with acute exacerbations of chronic bronchitis, the clinical response rate of 80% (59 out of 74) for cefprozil appeared superior to that of cefaclor at 62% (p = 0.067), whilst the bacteriological response rates were 62% (36 out of 58) for cefprozil and 74% (20 out of 27) for cefaclor. In pneumonia, the clinical response rates for cefprozil and cefaclor therapy were similar, 82% vs. 79%, although bacteriological eradication rates were better for cefprozil at 82% than for cefaclor at 71%. In the comparison of cefprozil with cefuroxime axetil, a total of 170 patients were evaluable. The clinical and bacteriological response rates for cefprozil of 95% and 100% were better than those for cefuroxime axetil 500 mg q. 12 hours of 84% and 75%, respectively. In the cefprozil vs. amoxicillin-clavulanate, 500 mg q. eight hours comparative study, the two antibiotics displayed no significant difference in clinical or bacteriological responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Penetration of cefprozil into middle ear fluid of patients with otitis media

Penetration of cefprozil into the middle ear fluid was investigated in patients with chronic otitis media. A total of 89 patients ranging from 7 months to 11 years old participated in the study. The middle ear fluid was removed by ventilation tubes inserted through the tympanic membrane at times ranging from 0.38 to 5.97 h after oral administration of a single dose of 15 or 20 mg/kg of body weight. A blood sample was also collected as soon as the middle ear fluid was removed. Plasma samples were analyzed for the concentration of cefprozil by a high-performance liquid chromatographic assay. Middle ear fluid samples were analyzed for the concentration of cefprozil by a microbiological assay. The concentrations of cefprozil in plasma ranged from 0.38 to 15.97 micrograms/ml at the 15-mg/kg dose level and from 1.28 to 21.47 micrograms/ml at the 20-mg/kg dose level. The corresponding middle ear fluid concentrations of cefprozil ranged from 0.06 to 4.44 micrograms/ml and from 0.17 to 8.67 micrograms/ml, respectively. Cefprozil penetrates well into middle ear fluid in patients with chronic otitis media.

Susceptibility of United States clinical trial isolates to cefprozil and cefaclor

First bacterial isolates (n = 2022) from patients enrolled in the United States cefprozil clinical trials were tested for susceptibility to cefprozil and cefaclor. Cefprozil was two- to eightfold more active than cefaclor against Gram-positive bacteria based on minimum inhibitory concentration (MIC50 and MIC90) values. The differential was greatest, for the most part, for the 80% of isolates of each species with the lowest MICs. Against Gram-negative bacterial species, the two cephalosporins were very similar in activity and MIC90 values ranged from 2 to 8 micrograms/ml for the most prevalent pathogens except Enterobacter spp., which were resistant. The majority of streptococci (98%) were susceptible to < or = 0.5 microgram/ml of cefprozil, and the majority of staphylococci tested (> 90%) were susceptible to < or = 4 micrograms/ml of cefprozil. These results for isolates primarily from community-acquired infections were similar to previously reported results from uncharacterized or hospital-associated isolates.

Update on clinical significance of coagulase-negative staphylococci

The clinical significance of coagulase-negative Staphylococcus species (CNS) continues to increase as strategies in medical practice lead to more invasive procedures. Hospitalized patients that are immunocompromised and/or suffering from chronic diseases are the most vulnerable to infection. Since CNS are widespread on the human body and are capable of producing very large populations, distinguishing the etiologic agent(s) from contaminating flora is a serious challenge. For this reason, culture identification should proceed to the species and strain levels. A much stronger case can be made for the identification of a CNS etiologic agent if the same strain is repeatedly isolated from a series of specimens as opposed to the isolation of different strains of one or more species. Strain identity initially can be based on colony morphology, and then one or more molecular approaches can be used to gain information on the genotype. Many of the CNS species are commonly resistant to antibiotics that are being indicated for staphylococcal infections, with the exception of vancomycin. The widespread use of antibiotics in hospitals has provided a reservoir of antibiotic-resistant genes. The main focus on mechanisms of pathogenesis has been with foreign body infections and the role of specific adhesins and slime produced by Staphylococcus epidermidis. Slime can reduce the immune response and opsonophagocytosis, thereby interfering with host defense mechanisms. As we become more aware of the various strategies used by CNS, we will be in a better position to compromise their defense mechanisms and improve treatment.

Interpretive accuracy of the disk diffusion method for testing newer orally administered cephalosporins against Morganella morganii

Eight newer orally administered cephems (cefdinir, cefetamet, cefixime, cefpodoxime, cefprozil, ceftibuten, cefuroxime, and loracarbef) were tested against 100 clinical strains of Morganella morganii to determine the extent of serious interpretive very major (false-susceptible) errors when current criteria for the disk diffusion test are applied. Agar dilution MICs and disk diffusion tests were performed as recommended by the National Committee for Clinical Laboratory Standards (Villanova, Pa.) (NCCLS), and the methods were compared by regression analysis using the method of least squares and by error rate bounding. The following results are listed in the order of increasing error rates: cefdinir, loracarbef, and cefprozil, < or = 1% very major error; ceftibuten, 8% minor errors; cefuroxime, 21% minor errors; cefixime, cefpodoxime, and cefetamet, very major errors of 15, 24, and 36%, respectively. M. morganii produces unacceptable rates of test error with cefuroxime, cefixime, cefpodoxime, and cefetamet. The latter two cephalosporins currently have NCCLS table footnote warnings covering the problem observed with this organism. The inclusion of cefuroxime and cefixime in the NCCLS table footnote is strongly recommended.

Effects of time of administration and posture on the pharmacokinetics of cefprozil

The effects of time of administration, sleep and posture on the pharmacokinetics of cefprozil were evaluated in a single-dose 3-way crossover study. After a 6-hour fast, 12 healthy male volunteers received oral cefprozil 250mg at 1200h (treatment A), 1200h (treatment B) and 2400h (treatment C) with a 7-day washout interval between each treatment. During the study period, volunteers receiving treatment A remained in a sitting/standing position or were ambulatory, those receiving treatment B were in the supine position, and those receiving treatment C were sleeping. Blood samples were taken over an 8-hour period and the plasma samples were analysed for the concentrations of cefprozil by a high performance liquid chromatography-ultraviolet method. Plasma concentration vs time data were analysed using noncompartmental analysis methods. Mean peak plasma concentrations (Cmax) were 4.51, 5.02 and 4.91 mg/L for treatments A, B and C, respectively. Corresponding mean values of the area under the plasma concentration-time curve (AUC(0-infinity)) were 12.6, 12.6 and 14.2 mg/L.h, respectively. The mean half-life (t1/2) values were 1.30, 1.23 and 1.50 hours for treatments A, B and C, respectively. Mean AUC(0-infinity), Cmax and t1/2 values following treatment B were not significantly different from those of treatment A. However, the mean AUC(0-infinity) and t1/2 values of cefprozil following treatment C were significantly greater than those of either treatment A or B. The mean Cmax value following treatment C was not significantly different than that of either treatments A or B. From these results, it was concluded that posture has no effect on the pharmacokinetics of cefprozil.(ABSTRACT TRUNCATED AT 250 WORDS)

Review of in vitro activity, pharmacokinetic characteristics, safety, and clinical efficacy of cefprozil, a new oral cephalosporin

OBJECTIVE

To review the pharmacokinetics, microbiology, clinical efficacy, safety, and tolerance of cefprozil, a new, broad-spectrum oral cephalosporin.

DATA SOURCES

Published clinical trials and microbiologic, pharmacokinetic, and safety data were identified by MEDLINE; additional references were derived from bibliographies of these articles; microbiologic data on file were provided by Bristol-Myers Squibb.

STUDY SELECTION

Only published comparative clinical trial reports are included in the review of clinical efficacy. Noncomparative clinical data pertaining to uses of cefprozil not approved by the Food and Drug Administration are not included.

DATA SYNTHESIS

Data are presented on the in vitro microbiologic activity of cefprozil against 10,152 bacterial isolates, including most of the clinically important streptococci (e.g., Streptococcus pyogenes, Streptococcus pneumoniae), beta-lactamase-positive and -negative Staphylococcus aureus and Haemophilus influenzae, Moraxella catarrhalis, Escherichia coli, Proteus mirabilis, Clostridium difficile, and numerous other gram-negative aerobes and anaerobes. In clinical trials, cefprozil appears to be at least as effective as commonly used comparison agents such as cefaclor, cefixime, and amoxicillin/clavulanic acid. Additionally, cefprozil is better tolerated than the latter two agents, especially with regard to gastrointestinal adverse effects.

CONCLUSIONS

Cefprozil is a broad-spectrum cephalosporin that provides coverage against both gram-negative and -positive bacteria that may cause otitis media, pharyngitis/tonsillitis, skin and skin-structure infections, secondary bacterial infection of acute bronchitis, and acute bacterial exacerbations of chronic bronchitis. The beta-lactamase stability of cefprozil appears to exceed that of other oral cephalosporins for some important pathogens. Cefprozil is used primarily for second-line treatment as less-expensive, first-line generic alternatives generally are available. Cefprozil demonstrates clinical advantages over many other orally administered beta-lactam antibiotics in terms of antimicrobial spectrum, a once- or twice-daily dosing regimen, and/or reduced incidence of adverse effects.

Penetration of cefprozil into tonsillar and adenoidal tissues

Penetration of cefprozil into tonsillar and/or adenoidal tissues was investigated for patients undergoing tonsillectomy and/or adenoidectomy. A total of 29 patients ranging in age from 2 to 14 years participated in the study. The tonsils and/or the adenoids were removed at times ranging from 0.33 to 3.17 h after oral administration of a dose of either 7.5 or 20 mg/kg of body weight. A blood sample was also collected as soon as the tissue sample was removed. Plasma, tonsil, and adenoid samples were analyzed for cis and trans isomers of cefprozil by high-performance liquid chromatographic assays. The concentrations of the cis isomer of cefprozil in plasma ranged from 0.60 to 9.87 micrograms/ml at the 7.5-mg/kg dose level and from 1.04 to 20.40 micrograms/ml at the 20-mg/kg dose level. The corresponding concentrations of the cis isomer in tonsil tissue ranged from 0.48 to 2.42 micrograms/g and from 1.00 to 4.29 micrograms/g, respectively. The corresponding concentrations of the cis isomer in adenoid tissue ranged from 0.40 to 4.20 micrograms/g and from 1.74 to 4.94 micrograms/g, respectively. The concentrations of the trans isomer were about 1/10 of those observed for the cis isomer. The median ratios of the cefprozil concentration in tonsillar tissue to that in plasma were 0.37 and 0.47 for patients receiving a 7.5- or a 20-mg/kg oral dose of cefprozil, respectively. The corresponding median ratios for the adenoidal tissue were 0.46 and 0.82, respectively. The cefprozil concentrations in either the tonsillar or the adenoidal tissue at both dose levels over 3.17 h after dosing are much higher than the MICs for common pathogens which cause pharyngitis or tonsillitis.

Cefprozil

Cefprozil is a new, orally bioavailable, cephalosporin with significant activity against the bacteria commonly associated with upper and lower respiratory tract infection, and skin and soft tissue infections. Its absorption and elimination dynamics suggest once- or twice-daily dosing. The low-rate of gastrointestinal and dermatologic side effects associated with cefprozil administration suggest that it may have a significant role in the management of patients with these infections. Children with pharyngitis or urinary tract infection are more appropriately treated with antibiotics having a narrower spectrum of activity. With a variety of newer cephalosporins being marketed in the early 1990s, it will be important for the clinician to examine the data from ongoing comparative clinical trials to determine which antibiotic is best for a patient with a specific infection and whether the added cost justifies its use.

Cefprozil. A review of its antibacterial activity, pharmacokinetic properties, and therapeutic potential

Cefprozil is an orally active cephalosporin which has demonstrated activity against a wide range of organisms in vitro. It is particularly active against the Gram-positive organisms Streptococcus pyogenes, pneumoniae and agalactiae and against methicillin-susceptible Staphylococcus aureus. Strains of methicillin-resistant S. aureus are not susceptible to cefprozil. Cefprozil is also moderately active against Haemophilus influenzae, Moraxella catarrhalis, Neisseria gonorrhoeae, many Enterobacteriaceae and certain anaerobic organisms, and is relatively stable to hydrolysis by a number of beta-lactamases. In comparative trials, the clinical and bacteriological efficacy of cefprozil 500mg or 20 mg/kg administered once or twice daily has been comparable with multiple daily dosage regimens of erythromycin in patients with tonsillitis or pharyngitis, with cefaclor and amoxicillin/clavulanate in lower respiratory tract infections, with amoxicillin/clavulanate and erythromycin in skin and skin-structure infections and with cefaclor in acute uncomplicated urinary tract infections. The clinical efficacy of cefprozil is similar to that of cefaclor in patients with tonsillitis or pharyngitis but the bacteriological efficacy of cefprozil is significantly greater than that of cefaclor. Cefprozil is clinically more effective than cefuroxime axetil in the treatment of lower respiratory tract infections and demonstrated greater efficacy than cefaclor in one of 2 comparative studies when administered twice daily in patients with skin and skin-structure infections. In children with acute otitis media, cefprozil 15 mg/kg twice daily was as effective as cefaclor or amoxicillin/clavulanate 13.3 mg/kg 3 times daily and was as effective as cefixime 8 mg/kg once daily. The most frequently reported adverse effects associated with cefprozil, diarrhoea and nausea, are usually mild to moderate in severity and discontinuation of treatment is rarely necessary. Thus, cefprozil with its convenient administration regimen appears to be a suitable alternative to cefaclor, cefixime, amoxicillin/clavulanate or erythromycin for the treatment of upper and lower respiratory tract infections, skin and skin-structure infections, and otitis media in children. While cefprozil has shown similar efficacy to cefaclor in the treatment of uncomplicated urinary tract infections, well-controlled clinical trials comparing its efficacy with that of cotrimoxazole (trimethoprim+sulfamethoxazole) in this indication are required.

Oral absolute bioavailability and intravenous dose-proportionality of cefprozil in humans

The absolute bioavailability (F) and dose proportionality of cefprozil were investigated in a parallel design study with an embedded two-way crossover leg. Twenty-four healthy male subjects divided into 3 dosing groups received a single 250-, 500-, or 1000-mg dose of cefprozil by a 30-minute intravenous infusion. Subjects assigned to the 500-mg dose group also received a 500-mg oral dose of cefprozil in crossover manner with a wash-out period of 7 days between each treatment. Cefprozil consists of cis and trans isomers in an approximate 90:10 ratio. Serial blood and urine samples were collected and analyzed for the concentrations of the cis and trans isomers of the cephalosporin using high-pressure liquid chromatographic assay with UV detection methods. After the 250-, 500-, and 1000-mg intravenous administration of cefprozil, the peak concentrations were 13.2, 26.0, and 48.5 micrograms/mL, and area under the plasma concentration versus time profiles were 17.2, 31.4, and 58.1 micrograms.hour/mL, respectively, for the cis isomer increasing in a dose proportional manner. Total body clearance, renal clearance, and volume of distribution at steady state, adjusted for body weight, were not significantly different among all groups. Mean residence time, elimination half-life, and urinary recovery were invariant with the dose. Based on the plasma and urine data, the estimates of F were 89% and 94% for the cis isomer, respectively. The plasma concentrations of the trans isomer were about 1/10th of the cis isomer, and all parameters were similar to those observed for the cis isomer. In summary, cefprozil exhibits linear pharmacokinetics and is essentially completely absorbed after oral administration.

In vitro activity of cefprozil (BMY 28100) and cefepime (BMY 28142) against Streptococcus pneumoniae, Branhamella catarrhalis, and Haemophilus influenzae, and provisional interpretive criteria for disk diffusion and dilution susceptibility tests with Haemophilus influenzae

The in vitro activities of two new cephalosporins, an oral agent, cefprozil and a parenteral compound, cefepime, were assessed against recent clinical isolates of Streptococcus pneumoniae, Moraxella (Branhamella) catarrhalis, and Haemophilus influenzae. In general, both cefprozil and cefepime MICs were higher for beta-lactamase-producing strains of M. catarrhalis in comparison to strains that lacked beta-lactamase. By contrast, beta-lactamase-positive and -negative strains of H. influenzae had similar cefprozil and cefepime minimum inhibitory concentrations (MICs). The MIC90 values for cefprozil were 0.12, 32, 4.0, and 0.5 micrograms/ml versus S. pneumoniae, H. influenzae, and beta-lactamase-positive and negative strains of M. catarrhalis, respectively. In comparison to three other oral cephalosporins included in this study, cefaclor, cefuroxime axetil, and cefixime, cefprozil was the most active agent against S. pneumoniae, the least active against B. catarrhalis, and equivalent in activity to cefaclor against H. influenzae. The cefepime MIC values against S. pneumoniae, H. influenzae, and beta-lactamase-positive and negative strains of M. catarrhalis were 0.03, 0.25, 2.0, and 0.5 micrograms/ml, respectively. Cefepime was less active than ceftriaxone for all three organism groups, however, was in all cases more active than cefixime, cefuroxime, cefaclor, and cefprozil.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetic interactions of cefprozil with food, propantheline, metoclopramide, and probenecid in healthy volunteers

Cefprozil, a new oral cephalosporin antibiotic, is composed of cis and trans isomers in an approximate 90:10 ratio. The objectives of this study were: (1) to assess the effects of alterations in gastrointestinal motility by metoclopramide and propantheline on the pharmacokinetics of cis and trans isomers of cefprozil, and to compare them with the effects of food on the pharmacokinetics of cefprozil; (2) to assess the effects of inhibition of renal tubular secretion by probenecid on the pharmacokinetics of cefprozil isomers. In this four-way crossover study, 15 healthy male volunteers received a 1000-mg dose of cefprozil after fasting, pretreatment with metoclopramide or propantheline, after breakfast, or after probenecid in an incomplete, balanced block design. There was a 1-week washout period between each treatment. Blood and urine samples collected over a 24-hour period were assayed for the cis and trans isomers. The concentrations of the trans isomers were generally 1/10 of the cis isomer. The means and variances of the pharmacokinetic parameters of the cis and trans isomers of cefprozil were similar in fasting subjects and were affected in a parallel manner by food, metoclopramide, propantheline, and probenecid. The pharmacokinetics of the cis isomer under the fasting condition were as follows: maximum peak plasma concentration (Cmax), 14.0 +/- 2.7 micrograms/mL; median time to reach Cmax (tmax), 1.5 (range, 1.0-3.5) hours; half-life (t1/2), 1.24 +/- 0.27 hours; area under the concentration (AUC0-infinity), 47.3 +/- 7.7 micrograms.hour/mL; mean residence time after oral administration (MRTpo), 2.9 +/- 0.4 hours; CLR, 219 +/- 60 mL/minute; and Xu% (percent cumulative urinary excretion in 0-24 hours), 68.1 +/- 12.5.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of antacid on the bioavailability of cefprozil

The effect of antacid on the bioavailability of cefprozil was investigated in a two-way crossover study. Eight healthy male subjects received a single 500-mg oral dose of cefprozil with and without coadministration of 30 ml of an antacid suspension containing magnesium hydroxide and aluminum hydroxide (Maalox). Cefprozil consists of cis and trans isomers in an approximate 90:10 ratio. When cefprozil was administered alone (treatment A), the mean maximum concentrations (Cmax) of the cis and trans isomers were 9.2 and 1.2 micrograms/ml, respectively. When cefprozil was coadministered with Maalox (treatment B), the Cmax values of the cis and trans isomers were 8.7 and 1.3 micrograms/ml, respectively. The mean values of the area under the curve from time zero to infinity (AUC0-infinity) were 27.7 and 3.5 micrograms.h/ml for treatment A and 27.5 and 3.5 micrograms.h/ml for treatment B for the cis and trans isomers, respectively. The other pharmacokinetic parameters, time to Cmax, elimination half-life, mean residence time, renal clearance, and percent urinary excretion, were essentially the same for the two isomers. The respective values of the elimination half-life for the cis and trans isomers were 1.36 and 1.32 h for treatment A and 1.36 and 1.42 h for treatment B. Mean urinary excretion was 63 and 60% for treatment A and 58 and 56% for treatment B for the cis and trans isomers, respectively. No significant differences between the two treatments were found for any of the pharmacokinetic parameters for either isomer. For the cis isomer, bioavailability point estimates (90% confidence intervals) of the mean Cmax and AUG0-infinity values for the Maalox treatment relative to those for the reference treatment were 95% (87%, 103%) and 99% (95%, 104%), respectively. For the trans isomer, the value were 109% (92%, 126%) for Cmax and 97% (88%, 106%) for AUC0-infinity. On the basis of the results of this study, it is concluded that the bioavailability of cefprozil is not affected by the coadministration of Maalox.

Excretion of cefprozil into human breast milk

The excretion of cefprozil into breast milk in nine healthy, lactating female subjects was investigated. Each subject received a single 1,000-mg oral dose of cefprozil consisting of cis and trans isomers in an approximately 90:10 ratio. Serial blood, urine, and breast milk samples were collected and analyzed for the concentrations of the cis and trans isomers by a specific high-pressure liquid chromatography-UV assay. The mean pharmacokinetic parameters for both isomers were essentially the same. The mean peak concentrations in plasma for the cis isomer were 14.8 micrograms/ml, and the area under the concentration curve was 54.8 micrograms.h/ml. The mean values of elimination half-life, renal clearance, and urinary excretion for the cis isomer were 1.69 h, 164 ml/min, and 60%, respectively. The mean concentrations in milk of the cis isomer over a 24-h period ranged from 0.25 to 3.36 micrograms/ml, with the maximum concentration appearing at 6 h after dosing. The average maximum concentration in milk of the trans isomer was less than 0.26 micrograms/ml. The concentrations of the trans isomer in plasma and in breast milk were about 1/10 of those for the cis isomer. Less than 0.3% of the dose was excreted in breast milk for both isomers of cefprozil. Even if one assumes that the concentration of cefprozil in milk remains constant at 3.36 micrograms/ml (the highest concentration of cefprozil observed in breast milk), an infant ingesting an average of 800 ml of milk per day will be exposed to a maximum amount of about 3 mg of cefprozil per day. This value represents about 0.3% of the maternal dose. Low excretion of cefprozil in breast milk and the excellent safety profile of cefprozil suggest that this cephalosporin may be administered to nursing mothers when indicated.

Absolute bioavailability of cefprozil after oral administration in beagles

The absolute bioavailability of cefprozil, a new oral cephalosporin, in four beagles was evaluated. In this two-way crossover study, each dog received a 125-mg dose of cefprozil either as an oral aqueous solution or as a 15-min intravenous infusion. A high-performance liquid chromatographic assay with UV detection was employed for the determination of cefprozil concentrations in plasma and urine. Key pharmacokinetic parameters were calculated by noncompartmental methods. Cefprozil was well absorbed after oral administration, and peak concentrations of 17.6 to 26.6 micrograms/ml were attained at 60 min after drug administration. The apparent elimination half-life of cefprozil was about 70 min. The renal clearance was about 60% of total body clearance and is suggestive of significant nonrenal clearance. The absolute bioavailability of cefprozil ranged from 67.1 to 79.1% in the dogs.

Multiple-dose pharmacokinetics of cefprozil and its impact on intestinal flora of volunteers

The pharmacokinetics of cefprozil were determined with 12 volunteers (8 received cefprozil and 4 received a placebo) after oral administration of 500 mg every 12 h over an 8-day period in a randomized, double-blind, placebo-controlled design. Concentrations in serum and urine were measured by high-pressure liquid chromatography and bioassay. The pharmacokinetic parameters were calculated on the basis of an open one-compartment model. The mean maximum concentration in serum on day 1 was 11.5 +/- 2.6 mg/liter, and the time to reach maximum concentration was 122.3 +/- 30 min after administration. Bioavailability parameters (area under the concentration-time curve from zero to infinity, maximum concentration of the drug in serum, and urinary recovery) indicated an excellent absorption. No accumulation over the 8-day period was registered. Cefprozil had a short biological elimination half-life of 58 +/- 10 min and a renal clearance of 210 +/- 51 ml/min, indicating high rates of renal excretion and tubular secretion. Analysis of the fecal flora showed an ecological impact of cefprozil on the intestinal microflora, such as a moderate decrease in enterobacteria and a slight increase in enterococci, staphylococci, and bacteroides during the study. The number of all bacterial species was already normalized 4 days after the administration period. The tolerance of cefprozil proved to be excellent; only a slight and reversible increase of liver enzymes (in two volunteers), mild cephalalgia, tiredness, and soft stool were registered during the 8-day period. Cefprozil had excellent absorption, no accumulation over an 8-day period, and only a limited impact on the intestinal microflora.

Comparison of cefprozil and cefaclor for treatment of acute urinary tract infections in women

A total of 108 college women with acute urinary tract infections were treated for 10 days with either 500 mg of cefprozil (BMY-28100-03-800) once a day (n = 72) or 250 mg of cefaclor three times a day (n = 36). Clinical and bacterial cure rates at 1 week posttherapy were 94 and 93%, respectively, for the cefprozil group and 94 and 94%, respectively, for the cefaclor group (P, not significant). Both cefprozil and cefaclor were safe and effective.

Simultaneous high-performance liquid chromatographic analysis of cefprozil diastereomers in a pharmacokinetic study

Cefprozil, a new oral cephalosporin, consists of a 90:10 cis:trans isomer mixture. Sensitive, specific and reproducible high performance liquid chromatographic methods have been developed for the simultaneous quantification of the two stereoisomers of cefprozil in plasma and urine samples from human and rats. Cephalexin acted as the internal standard. Plasma protein was precipitated with acetonitrile and trichloracetic acid with subsequent extraction of acetonitrile. After vortexing and centrifuging, the aqueous phase was injected onto a reverse phase C8 column. Urine samples were acidified with sodium acetate buffer (pH 3.8) and then directly injected onto a reverse phase C18 column. The detector was set at 280 nm. These methods were applied to determine protein binding of both isomers in human and rat sera, and to perform a pharmacokinetic study in human. Results showed that both isomers bound moderately to serum proteins with no interference by the other isomer. The pharmacokinetic study in human indicated that cefprozil was well absorbed and the cis and trans isomers have similar pharmacokinetics.

Comparative efficacy and safety of cefprozil (BMY-28100) and cefaclor in the treatment of acute group A beta-hemolytic streptococcal pharyngitis

Cefprozil (BMY-28100) is a semisynthetic cephalosporin with broad-spectrum antibacterial activity and prolonged serum elimination half-life allowing for once-a-day oral administration. In vitro, cefprozil demonstrates excellent activity against Staphylococcus aureus, Streptococcus pyogenes, Haemophilus influenzae, and Moraxella catarrhalis. Cefprozil (500 mg once daily) was compared to cefaclor (250 mg three times daily) in an open, randomized, comparative trial for the treatment of acute group A beta-hemolytic streptococcal pharyngitis. Ninety-four patients were enrolled in this study; 53 patients were evaluable for clinical and bacteriological response assessment. Seventy-eight patients were evaluable for safety assessment. Three patients (all in the cefprozil treatment group) required disenrollment because of side effects, mainly nausea. Clinical and bacteriological responses were comparable for both study drugs. Leukopenia and nausea, the most common side effects observed, were more common in the cefprozil-treated group. Cefprozil appears to be an appropriate alternative to cefaclor for the treatment of acute group A beta-hemolytic streptococcal pharyngitis. However, because of the small number of patients eligible for efficacy assessment, a large type II (beta) error was expected in our study, which may have resulted in a potential failure to detect a difference between both treatment groups. A larger study would be required to determine the proper role of cefprozil in the treatment of group A beta-hemolytic streptococcal infections.

Pharmacokinetics of cefprozil in healthy subjects and patients with hepatic impairment

The pharmacokinetics of cefprozil were studied in 12 (9 men, 3 women) subjects with hepatic impairment and in 12 healthy subjects who were matched for age, sex, and weight. Each subject received a single 1000 mg oral dose of cefprozil, which consists of cis and trans isomers in approximately a 90:10 ratio. Serial blood and urine samples were collected and analyzed using validated HPLC/UV methods for the concentration of each isomer. The results of the plasma and urine analyses were subjected to noncompartmental pharmacokinetic analysis. The values for the peak plasma concentrations (Cmax), area under the plasma concentration versus time curve (AUC0-infinity), apparent total body clearance (Clt/F), renal clearance (Clr), and percent of drug excreted in urine (%UR) of each isomer were not significantly different in healthy subjects and patients with hepatic impairment. The only parameters that were significantly (P less than or equal to .05) longer in patients with hepatic impairment were mean residence time in the body (MRT) and half-life; the MRT for the cis isomer in healthy subjects and subjects with hepatic impairment were 3.33 hr and 3.88 hr, respectively, and for the trans isomer 3.17 hr and 3.68 hr; the half-life for the cis isomer was 1.62 hr and 2.22 hr, respectively, and for the trans isomer 1.21 hr and 1.54 hr. The pharmacokinetics of the cis and trans isomers of cefprozil were virtually identical in healthy subjects as well as those with hepatic impairment.

Pharmacokinetics of cefprozil in healthy subjects and patients with renal impairment

Cefprozil, a new broad-spectrum oral cephalosporin, is composed of cis and trans isomers in an approximate 90:10 ratio. The pharmacokinetics of a single oral 1000-mg dose of cefprozil were evaluated in 6 healthy subjects and 24 patients with various degrees of renal impairment. Six of these subjects were studied both while receiving hemodialysis and during an interdialytic period. Plasma, urine, and hemodialysate that were collected at predetermined times were analyzed for concentrations of the cis and trans isomers of cefprozil using reverse-phase HPLC assay with UV detection. The maximum plasma concentration of the cis isomer ranged from 12.3 micrograms/mL in subjects with normal renal function to 36.7 micrograms/mL in hemodialysis patients. Similarly the area under the plasma concentration-time curve and the elimination half-life increased from 46 micrograms.h/mL to 373 micrograms.h/mL and from 1.72 hours to 5.94 hours, respectively. Renal clearance of the cis isomer decreased from 198 mL/min in normal subjects to 19 mL/min in volunteers with creatinine clearances of less than or equal to 30 mL/min; there was a strong correlation (r2 greater than or equal to .93) between the renal clearance of the cis isomer and creatinine clearance. Urinary recovery of the cis isomer decreased from 57% in those with normal renal function to 24% in the group with a creatinine clearance of less than or equal to 30 mL/min. Hemodialysis decreased the half-life of the cis isomer to 2 hours and removed approximately 55% of it from the body during a 3-hour dialysis period (hemodialysis clearance equaled approximately 87 mL/min). The pharmacokinetics of the trans isomer were similar to those observed for the cis isomer and were affected similarly by declining renal function. A reduction in dosage is recommended in patients with a creatinine clearance of 30 mL/min or less. It may be necessary to administer a dose after hemodialysis to maintain therapeutic plasma concentrations.

Pharmacokinetics of cefprozil in infants and children

Twenty pediatric patients (ages, between 8 months and 8 years) received a single oral dose of cefprozil at levels of 15 and 30 mg/kg of body weight. Cefprozil consists of cis (BMY-28100) and trans (BMY-28167) isomers in an approximately 90:10 ratio. Six plasma samples were collected from each pediatric patient and assayed for drug concentrations. As measured by a microbiological assay, peak concentrations of 11.16 and 15.93 micrograms of cefprozil per ml occurred at 1 h for patients who received the 15- and 30-mg/kg doses, respectively. The respective mean half-lives of cefprozil were 1.77 and 2.14 h, and the respective mean areas under the curve were 28.05 and 45.28 micrograms.h/ml for patients who received the 15- and 30-mg/kg doses. When measured by a high-pressure liquid chromatography method, peak concentrations of 12.09 and 18.04 micrograms of the cis isomer per ml were obtained at 1 h, with mean half-lives of 1.63 and 2.06 h and mean areas under the curve of 30.48 and 49.34 micrograms.h/ml in patients who received the 15- and 30-mg/kg doses, respectively. For the trans isomer, peak concentrations of 1.16 and 1.63 micrograms/ml occurred at 1 h, respectively, with mean half-lives of 1.61 and 1.65 h and mean areas under the curve of 2.89 and 4.34 micrograms.h/ml in patients who received the 15- and 30-mg/kg doses, respectively.

Comparison of the effects of food on the pharmacokinetics of cefprozil and cefaclor

The objective of this study was to assess the effects of food on the pharmacokinetics of cefprozil and cefaclor. A group of 12 healthy male volunteers received a single 250-mg dose of cefprozil or cefaclor under fasting conditions as well as after the intake of food. There was a 1-week washout period between each treatment. Serial blood samples were collected and assayed for cefprozil or cefaclor by specific high-pressure liquid chromatographic methods. The mean +/- standard deviation peak concentration (Cmax) of cefprozil in plasma was 6.13 +/- 1.22 micrograms/ml under the fasting condition and 5.27 +/- 1.06 micrograms/ml after breakfast, and these values were not significantly different from each other. The corresponding median time to reach Cmax was prolonged after food intake, but this difference was not significant. The mean Cmax values of cefaclor decreased significantly from 8.70 +/- 2.72 micrograms/ml under the fasting condition to 4.29 +/- 1.52 micrograms/ml after breakfast, and the corresponding median times to reach Cmax were significantly prolonged. The mean half-lives of cefprozil and cefaclor were nearly identical for the two treatments, suggesting that the elimination kinetics of these cephalosporins remained unaltered when the drugs were administered with food. The area under the plasma-concentration-versus-time curves for fasted and fed conditions were not significantly different for both drugs. The results of this study indicate that the extent of absorption and rate of elimination of both cephalosporins remain unaltered in the presence of food. However, the absorption rate of cefaclor is significantly reduced in the presence of food, while that of cefprozil remains unaltered. As a result, the Cmax of cefaclor is significantly reduced in the presence of food, whereas that of cefprozil is not significantly affected. Cefprozil can be administered with a meal without markedly affecting levels in blood.

Phase I study of multiple-dose cefprozil and comparison with cefaclor

The objectives of this study were to assess the safety and tolerance of cefprozil, to characterize the pharmacokinetics of cefprozil after administration of multiple doses of the drug, and to compare these pharmacokinetic parameters with those obtained with cefaclor. The volunteers received 28 doses of 250, 500, or 1,000 mg of cefprozil or 500 mg of cefaclor every 8 h for 10 days. Serial blood samples and the total volume of urine voided by each individual were collected for pharmacokinetic evaluation on days 1, 5, and 10. Both cephalosporins were well tolerated after multiple oral dosing. The peak levels in plasma (Cmax) of cefprozil ranged from 5.7 to 18.3 micrograms/ml after oral administration of 250- to 1,000-mg doses. The regression analysis of Cmax on cefprozil dose showed a dose-linear response. The mean Cmax of cefaclor ranged from 15.2 to 16.7 micrograms/ml and did not change significantly on multiple dosing. The overall mean terminal half-life of cefprozil was 1.2 h and was invariant with respect to dose or duration of dosing. The area under the plasma-concentration-versus-time curve from 0 h to infinity (AUC0-infinity) of cefprozil increased in a dose-proportional manner with an increase in dose. The overall urinary recovery (61% of dose) and renal clearance values of cefprozil were generally invariant with respect to dose and duration of dosing. While cefprozil was apparently absorbed less rapidly and achieved lower Cmax values than cefaclor, the AUC0-infinity of cefprozil was nearly twofold greater than that of cefaclor. The half-life of cefprozil was also twofold longer than that observed for cefaclor. Although the urinary recovery of cefaclor (75% of dose) was significantly higher than that of cefprozil (61% of dose), the concentrations of cefprozil in urine remained significantly higher than those of cefaclor from 2 to 8 h postdosing. If the therapeutic concept is maintained that levels of beta-lactam antibiotics in plasma should exceed the MIC for the offending organisms over a period that approximates the dosing interval, then cefprozil would appear to be suitable for twice-daily administration, whereas cefaclor should probably be administered three or even four times a day.

Comparison of cefprozil and cefaclor pharmacokinetics and tissue penetration

The pharmacokinetics and tissue penetration, as judged by skin blister fluid, of cefprozil and cefaclor were examined in 12 healthy male volunteers. Doses of 250 and 500 mg of each drug were given to fasting subjects in a crossover fashion. Serially obtained plasma, skin blister fluid, and urine samples were analyzed for cefprozil or cefaclor by validated high-pressure liquid chromatographic methods. After oral administration of 250 and 500 mg of cefprozil, mean concentrations in plasma rose to peak levels (Cmax) of 6.1 and 11.2 micrograms/ml, respectively, and those of cefaclor were 10.6 and 17.3 micrograms/ml, respectively. The elimination half-life of cefprozil (1.3 h) was significantly longer than that of cefaclor (0.6 h), and as a result, the area under the curve for cefprozil was about two times greater than that for cefaclor. Both cephalosporins were primarily excreted unchanged in urine. The mean skin blister Cmax values were 3.0 and 5.8 micrograms/ml for cefprozil and 3.6 and 6.5 micrograms/ml for cefaclor after the 250- and 500-mg oral doses, respectively. The mean Cmax values in skin blister fluid for both cephalosporins were comparable and were significantly lower than the corresponding Cmax values in plasma. However, the levels of cefprozil and cefaclor in skin blister fluid declined more slowly than they did in plasma. The skin blister fluid half-life estimates for cefprozil were significantly longer than they were for cefaclor. Parallel to the observation in plasma, the mean skin blister fluid areas under the curve for cefprozil were significantly higher than they were for cefaclor. The plasma and skin blister fluid pharmacokinetic analyses suggest that the exposure of humans to cefprozil is significantly greater than that to cefaclor at the same dose.

Comparative in vitro activities of several new fluoroquinolones and beta-lactam antimicrobial agents against community isolates of Streptococcus pneumoniae

The in vitro susceptibilities of 551 community isolates of Streptococcus pneumoniae from the Canadian province of Ontario to several new fluoroquinolones and beta-lactam antimicrobial agents were determined by a broth microdilution technique. Eight (1.5%) of these isolates were moderately susceptible (MICs, greater than or equal to 0.12 and less than or equal to 1.0 microgram/ml) to penicillin; none was resistant. Temafloxacin, ciprofloxacin, and ofloxacin (MICs for 90% of strains tested, between 1 and 2 micrograms/ml) were the most active fluoroquinolones tested, and BMY-28100 (MIC for 90% of strains tested, 0.25 microgram/ml) was the most active of the new beta-lactams tested.

Phase I study of single-dose BMY-28100, a new oral cephalosporin

The objective of this Phase I study was to evaluate the safety, tolerance, and pharmacokinetics of BMY-28100 in 36 male subjects after the administration of single oral doses of 250, 500, and 1,000 mg. The subjects were divided into groups of 12 per dose group. All subjects completed the study, and BMY-28100 was well tolerated at all doses. The maximum concentration of the drug in plasma ranged from 6.2 to 17.7 micrograms/ml for the 250- and 1,000-mg doses, respectively, and the area under the curve increased in a dose-proportional manner. The elimination half-life and renal clearance averages were 1.2 h and 200 ml/min, respectively. The values for renal clearance suggest that BMY-28100 is excreted by glomerular filtration and tubular secretion. Mean concentrations of the drug in urine were highest during the first 4 h after the doses and ranged from 175 to 658 micrograms/ml following the 250- and 1,000-mg doses, respectively. The mean urinary recovery ranged from 57 to 70% of the dose. The results from this Phase I study indicate that BMY-28100 is well tolerated and exhibits linear pharmacokinetics.

Antimicrobial activity, spectrum, and recommendations for disk diffusion susceptibility testing of ceftibuten (7432-S; SCH 39720), a new orally administered cephalosporin

The antimicrobial activity and spectrum of ceftibuten (7432-S; SCH 39720) was determined on a wide variety of bacterial species selected for resistance to oral and parenteral beta-lactam antimicrobial agents. Ceftibuten was found to be the most active beta-lactam tested against members of the family Enterobacteriaceae, inhibiting 81.6% of strains at less than or equal to 8.0 micrograms/ml compared with 75.0 and 54.8% of strains inhibited by cefixime and cefuroxime, respectively. All strains of Haemophilus influenzae (MIC for 90% of strains [MIC90], less than or equal to 0.06 microgram/ml), Branhamella catarrhalis (MIC90, 3.0 micrograms/ml), and pathogenic Neisseria spp. (MIC90, less than or equal to 0.06 and 0.019 microgram/ml) were susceptible to ceftibuten. Beta-hemolytic Streptococcus spp. (serogroups A, B, C, and G) were also inhibited by ceftibuten, but penicillin-resistant pneumococci were generally resistant to cefixime and ceftibuten. The activity and spectrum of ceftibuten seem most applicable to infections of the respiratory and urinary tract plus those infections caused by pathogenic Neisseria spp. Ceftibuten disks (30 micrograms) were evaluated and found to have an acceptable correlation (r = 0.88) with ceftibuten MICs. Preliminary zone size interpretive criteria for MIC breakpoints of less than or equal to 4.0 and less than or equal to 8.0 micrograms/ml were calculated.

Comparative in vitro activity of the new oral cephalosporin cefixime

Cefixime was 8 to 10 times more active than cefaclor and augmentin against isolates of Escherichia coli, Klebsiella pneumoniae and Salmonella typhi, MIC90 values ranging from 0.06 to 0.25 micrograms/ml. However, none of these three drugs was particularly active against isolates of more resistant gram-negative bacilli such as Enterobacter, Serratia, Citrobacter, Acinetobacter, Providencia and Achromobacter spp. The lowest MIC values for gram-negative bacilli were seen with ciprofloxacin, except for isolates of Acinetobacter, where cotrimoxazole was the most active of the five drugs studied. Augmentin and ciprofloxacin exhibited the lowest MICs for isolates of streptococci and corynebacteria. Although cefixime may be among the most active oral beta-lactam drugs, it does not appear to be useful for treatment of infections caused by more resistant gram-negative bacilli.

Antimicrobial activity and disk diffusion susceptibility testing of U-76,253A (R-3746), the active metabolite of the new cephalosporin ester, U-76,252 (CS-807)

Compound U-76,253A (R-3746), the active metabolite sodium salt of the prodrug ester U-76,252 (CS-807), was demonstrated to be active against members of the family Enterobacteriaceae with 82 and 85% of strains inhibited by less than or equal to 2.0 and less than or equal to 4.0 micrograms/ml, respectively. In addition, U-76,253A inhibited all strains of Branhamella catarrhalis, Haemophilus influenzae, pathogenic Neisseria spp., oxacillin-susceptible Staphylococcus aureus, beta-hemolytic streptococci, and pneumococci at less than or equal to 4.0 micrograms/ml. Pseudomonas spp., Acinetobacter spp., enterococci, and oxacillin-resistant staphylococci were resistant to U-76,253A. This U-76,253A antimicrobial activity and spectrum was generally superior to that of comparison orally administered cephems (cefaclor, cefuroxime, and cefixime) and the amoxicillin-clavulanic acid combination. Tests with beta-lactamase-producing isolates indicated that U-76,253A was bactericidal and that its MICs were only influenced by high inoculum concentrations (10(7) CFU/ml) against type Ia and IVc enzyme-producing strains. Preliminary disk diffusion interpretive zone criteria were calculated for 10- and 30-micrograms U-76,253A disks and several possible susceptible MIC breakpoints. The absolute interpretive agreement between MICs and zone diameters ranged from 87.8 to 95.6%. Final selection of interpretive criteria awaits further U-76,252 pharmacokinetic information.

Disk diffusion susceptibility testing for LY163892 (KT-3777), a new orally administered 1-carbacephem

LY163892, a new orally administered 1-carbacephem, was found to have a spectrum of antimicrobial activity very similar to that of cefaclor. Diffusion tests with 30-micrograms LY163892 disks produced acceptable interpretive error rates with greater than or equal to 22 mm as the susceptibility zone diameter. This was required to reduce potential false-susceptibility results, particularly among Enterobacter spp. and Providencia stuartii: both species included strains that produce beta-lactamases capable of hydrolyzing Ly163892. Preliminary recommendations for LY163892 disk tests are presented, but the continued use of the 30-micrograms cephalothin "class representative" disk might be the best procedure to minimize LY163892 interpretive errors for clinical trials. A separate LY163892 disk for testing Haemophilus influenzae strains should be seriously considered.

BMY-28100, a new oral cephalosporin: antimicrobial activity against nearly 7,000 recent clinical isolates, comparative potency with other oral agents, and activity against beta-lactamase producing isolates

The antimicrobial activity of BMY-28100 was tested against approximately 7,000 bacterial pathogens in a multicenter, multiphased collaborative investigation. The BMY-28100 spectrum and antimicrobial potency was most similar to that of cefaclor and superior to that of cephalexin among currently available cephalosporins. Species that had greater than or equal to 90% of clinical strains inhibited by BMY-28100 (less than or equal to 8.0 micrograms/ml) were: Citrobacter diversus, Escherichia coli, Klebsiella spp., Proteus mirabilis, Salmonella spp., Branhamella catarrhalis, Haemophilus influenzae, Neisseria gonorrhoeae, N. meningitidis, methicillin-susceptible Staphylococcus supp., Streptococcus pneumoniae, S. pyogenes, S. agalactiae, S. bovis, serogroup C and G streptococci, Listeria monocytogenes and gm-positive anaerobes. BMY-28100 inhibited 9% more of the 6286 fresh clinical isolates at less than or equal to 8.0 micrograms/ml than cefaclor at the same concentration. BMY-28100 was generally bactericidal, but MICs for some species were markedly increased when an inoculum concentration of 10(7) CFU/ml was used. Strains producing plasmid-mediated beta-lactamases (TEM, OXA, SHV, HMS) were susceptible to BMY-28100, cefaclor, and cefuroxime. BMY-28100 was less active against strains producing chromosomal-mediated beta-lactamases (Types I and IV). BMY-28100 was not hydrolyzed significantly by the tested plasmid-mediated beta-lactamases, but was destroyed by Type I cephalosporinases and Klebsiella K1 enzymes.

Antimicrobial activity of U-76,252 (CS-807), a new orally administered cephalosporin ester, including recommendations for MIC quality control

U-76,253A (R-3746), the active metabolite of the new cephalosporin ester, U-76,252 (CS-807), was tested against 4,742 fresh clinical isolates from four large medical centers. U-76,253A was very active against nearly all species of Enterobacteriaceae (87.7% inhibited at less than or equal to 4.0 micrograms/ml). Staphylococcus spp., and the streptococci. The U-76,253A spectrum was superior to the comparison orally administered cephalosporins (cephalexin, cephradine, cefaclor). Pseudomonas spp., Acinetobacter spp., and the enterococci were resistant to U-76,253A and the other tested drugs. Broth microdilution MIC quality control (QC) limits were established for U-76,253A in a multilaboratory investigation using a minimum of 125 MIC determinations per organism. The following MIC QC ranges were recommended; Escherichia coli (ATCC 25922) = 0.25-1.0 micrograms/ml, Staphylococcus aureus (ATCC 29213) = 2.0-4.0 micrograms/ml and Pseudomonas aeruginosa (ATCC 27853) = greater than 32 micrograms/ml.

In vitro evaluations of U-76,252 (CS-807): antimicrobial spectrum, beta-lactamase stability, and enzyme inhibition

Compound U-76,252 (Upjohn) is a cephalosporin ester that enhances oral absorption of the active free acid cephem, U-76,253. The active form structurally resembles parenteral aminothiazolyl-methoxyimino cephalosporins such as cefotaxime and its desacetyl metabolite. The g-negative antimicrobial activity of U-76,253 A (sodium salt of U-76,253) was most similar to that of cefixime and more potent than that of cefaclor or cefuroxime among the orally administered cephalosporins. Against g-positive bacteria, U-76,253 A was more active than cefixime. U-76,253 A was relatively stable to hydrolysis by five beta-lactamases (Type Ia, TEM-1, K1, CARB-2, and OXA-1), a stability most similar to cefotaxime and superior to that of cefaclor. Only the Type Ia (P99) enzyme was significantly inhibited by U-76,253 (IC 50 = 2.0 microM).

Disk diffusion susceptibility testing and broth microdilution quality control guidelines for BMY-28100, a new orally administered cephalosporin

The BMY-28100 30-micrograms-disk test was evaluated by using 615 clinical isolates. Regression analyses and error rates were determined, leading to the recommendation of greater than or equal to 18-mm zone diameters (MIC correlate, greater than or equal to 8.0 micrograms/ml) for susceptibility and less than or equal to 14-mm zone diameters (MIC correlate, greater than or equal to 32 micrograms/ml) for resistance. Nearly all false-susceptible disk test results were among the Providencia spp. and the beta-lactamase-positive Haemophilus influenzae strains. Susceptibility disk test results for these species should be interpreted with caution. The following broth microdilution MIC quality control guidelines were determined from results of a multilaboratory trial: Escherichia coli ATCC 25922, 1.0 to 4.0 micrograms/ml; Enterococcus faecalis ATCC 29212, 4.0 to 16 micrograms/ml; Staphylococcus aureus ATCC 29213, 0.25 to 1.0 microgram/ml; and Pseudomonas aeruginosa ATCC 27853, greater than 32 micrograms/ml.

Beta-lactamase hydrolysis and inhibition studies of the new 1-carbacephem LY163892

A novel 1-carbacephem, LY163892, was determined to be more stable to plasmid-mediated beta-lactamases than cefaclor. Chromosomal-mediated Type Ia and IVc enzymes destroyed LY163892 at rates ranging from 16 to 93% that of nitrocefin. LY163892 showed minimal ability to inhibit beta-lactamases other than Type Ia (P99).

In vitro activity and beta-lactamase stability of the oral cephalosporin BMY-28100

BMY-28100 was compared with cephalexin, cefaclor, cefixime, and cefteram and found to be more active than the reference cephalosporins against Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus faecalis, and Clostridium difficile. BMY-28100 was the next most active, after cefteram, against Streptococcus pyogenes and Streptococcus pneumoniae. Against gram-negative bacteria, BMY-28100 showed similar activity to that of cefaclor. The antimicrobial activity of BMY-28100, including bactericidal activity, against Staphylococcus aureus was less affected by penicillinase-production than was that of cefaclor. BMY-28100 was more stable than cefaclor against various types of penicillinases, especially against the penicillinase from Staphylococcus aureus.