Influence of storage and susceptibility test conditions on stability and activity of LY163892 and four other cephalosporins

Bioequivalence evaluation of two brands of cefaclor 500 mg capsules: quantification of cefaclor using solid phase extraction technique

OBJECTIVE

To assess the bioequivalence of two cefaclor 500 mg capsule formulations, and to develop a new high performance liquid chromatographic (HPLC) method using solid phase extraction technique for the quantification of cefaclor in human plasma.

METHOD

An open, randomized, two-way, crossover trial with a one-week washout period in 25 healthy volunteers. The two commercial brands used were Recocef(Julphar, United Arab Emirates) as test and Ceclor(Eli Lilly, UK) as reference product. The drug was administered with 240 mL of water after a 10-h overnight fast. After dosing, serial blood samples were collected for a period of 8 h. Plasma harvested from blood was analysed for cefaclor by a new HPLC method using a solid phase extraction technique. The limit of detection of cefaclor was 17.6 ng/mL; average recovery was 96.5%; the intraday CV was less than 8% and interday CV was less than 13%. Various pharmacokinetic parameters, including AUC0-t, AUC0-infinity, Cmax, Tmax, T1/2, and Kel, were determined from plasma concentrations for both formulations. Statistical analysis (ANOVA and 90% confidence intervals) were applied to AUC0-t, AUC0-infinity and Cmax for bioequivalence evaluation of two brands. The new HPLC method with solid phase extraction circumvented the problem of mixed polarity of cefaclor and facilitated its extraction from the complex plasma matrix while keeping the background free from interference due to endogenous plasma compounds.

RESULTS

No significant difference was observed between the two brands of cefaclor capsules.

CONCLUSION

Recocef was judged bioequivalent to Ceclor and the two products can therefore be considered to be interchangeable in medical practice.

Loracarbef: a new orally administered carbacephem antibiotic

OBJECTIVE

To discuss the in vitro activity, pharmacokinetics, clinical efficacy, adverse effects, and relative merits of loracarbef, a new orally administered carbacephem antibiotic.

DATA SOURCES

Pertinent literature was identified by a review of selected journals and a MEDLINE search. Additional information was provided by the manufacturer of loracarbef.

STUDY SELECTION

All studies that have evaluated the clinical efficacy of loracarbef were included. In vitro studies were included if they used similar methodologies. Additional information was incorporated regarding the chemistry, pharmacokinetics, and adverse effects of loracarbef.

DATA SYNTHESIS

Loracarbef has antibacterial activity against most community-acquired respiratory tract, skin and skin structure, and urinary tract pathogens. The drug is well absorbed after oral administration and plasma concentrations achieved in patients are greater than the in vitro minimum inhibitory concentrations for most of the above bacteria. Although the majority of the clinical studies with loracarbef have methodologic deficiencies, loracarbef therapy has demonstrated similar efficacy in the treatment of upper respiratory tract (except otitis media), lower respiratory tract, skin and skin-structure, and urinary tract infections compared with accepted antibiotics. Potential advantages of the new carbacephem may be improved patient compliance with its less frequent dosing schedule (once or twice a day, depending on the infection), and a low incidence of adverse effects.

CONCLUSIONS

Preliminary data indicate that loracarbef may be an alternative agent for the treatment of a variety of community-acquired infections. Additional clinical experience and rigorously controlled comparative clinical trials are necessary to enable practitioners to fully define the therapeutic role of loracarbef.

Molecular basis of the efficacy of cefaclor against Haemophilus influenzae

Cefaclor sustained its inhibitory activity against a beta-lactamase-producing strain of Haemophilus influenzae. Although a relatively high permeability coefficient was calculated for ampicillin compared with that calculated for cefaclor, the resulting periplasmic concentration of cefaclor was 5.7 times that of ampicillin. The efficacy of cefaclor may be due to its higher beta-lactamase resistance, which allows it to achieve a greater periplasmic concentration and adequate binding to crucial penicillin-binding proteins.

Loracarbef versus penicillin V in the treatment of streptococcal pharyngitis and tonsillitis

Ten-day, double-blind, randomized, parallel treatment regimens of loracarbef (200 mg capsule twice daily or 15 mg/kg/day oral suspension in two divided doses up to a maximum of 375 mg/day; n = 169) and penicillin V (250 mg capsule four times daily or 20 mg/kg/day suspension in four divided doses up to a maximum of 500 mg/day; n = 175) were compared in the treatment of group A beta-haemolytic streptococcal (GABHS) pharyngitis and tonsillitis. Post-therapy clinical responses were similar for evaluable patients in both treatment groups: 97.4% of the loracarbef group (101/115 patients cured and 11/115 improved) and 96.0% of the penicillin group (101/124 patients cured and 18/124 improved). A statistically significant difference in the pathogen elimination rate was noted between treatment groups: post-therapy throat cultures were negative for GABHS in 94.8% (109/115) of loracarbef-treated patients compared with 87.1% (108/124) of penicillin-treated patients (p = 0.040). Loracarbef and penicillin V were comparable in terms of safety. Headache and nausea/vomiting were the most common events reported during therapy (nausea/vomiting were slightly less common in the loracarbef group). Three patients in each group were discontinued from the study due to drug-related adverse events; one due to rash in the loracarbef group and one due to rash and one due to vomiting in the penicillin group. These data support the conclusion that loracarbef twice daily is more effective in eradicating GABHS than penicillin V four times daily, and the two drugs are comparable in safety and clinical efficacy in the treatment of GABHS pharyngitis and tonsillitis.

Loracarbef (LY163892) versus cefaclor and norfloxacin in the treatment of uncomplicated pyelonephritis

Optimal therapy for pyelonephritis requires the immediate administration of an effective broad-spectrum antibiotic. Because conventional oral antibiotics such as the sulfonamides and the aminopenicillins are limited by the development of resistant bacteria associated with this common disease, the therapeutic effectiveness of a new oral carbacephem antibiotic was investigated. Two double-blind, randomized clinical trials of loracarbef (LY163892) were conducted. A total of 245 patients (greater than or equal to 18 years old) with uncomplicated pyelonephritis were enrolled in parallel studies. One study compared loracarbef with cefaclor; the other compared loracarbef with norfloxacin. In the combined patient population, 119 patients were treated with loracarbef (400 mg twice daily), 43 with cefaclor (500 mg three times daily), and 83 with norfloxacin (400 mg twice daily). All treatment regimens continued for greater than or equal to 14 days. A total of 68 patients in the loracarbef group, 25 in the cefaclor group, and 43 in the norfloxacin group qualified for efficacy analysis. Escherichia coli was the causative pathogen in 85.0% of these patients. Successful posttherapy clinical and bacteriologic responses were similar for all three study drugs: 94.1 and 86.8%, 96.0 and 80.0%, 97.7 and 88.4% for loracarbef, cefaclor, and norfloxacin, respectively. Late posttherapy clinical responses were 87.4, 83.3, and 91.7% for the loracarbef, cefaclor, and norfloxacin groups, respectively. Bacteriologic responses for the three groups were 79.6, 60.0, and 88.9%. The most frequent adverse effects (headache, diarrhea, and nausea) were experienced by three patients (2.5%) in the loracarbef group; headaches were noted in two (4.7%) cefaclor patients, diarrhea was noted in three (7.0%) patients in the cefaclor group, and nausea was noted in four (9.3%). Gastrointestinal events were noted in four patients (4.8%) in the norfloxacin group. The data demonstrate that loracarbef is comparable in efficacy and safety to both cefaclor and norfloxacin as oral therapy for uncomplicated pyelonephritis.

Comparison of loracarbef (LY163892) versus amoxicillin in the treatment of bronchopneumonia and lobar pneumonia

Loracarbef (LY163892), a carbacephem, is the first of a new class of beta-lactam compounds. A 14-day, double-blind, randomized, parallel treatment study compared loracarbef (400 mg b.i.d.; n = 169) and amoxicillin (500 mg t.i.d.; n = 167) in the treatment of lobar pneumonia and bronchopneumonia. Forty-four patients in the loracarbef group and 40 patients in the amoxicillin group were evaluable for efficacy analysis. Streptococcus pneumoniae and Haemophilus influenzae were isolated from pure or mixed cultures in 45.5% of the evaluable patients, with S. pneumoniae being isolated most frequently. Favourable clinical responses (cure or improvement) in the loracarbef-treated group (42/44; 95.5%) were similar to those in the amoxicillin-treated group (38/40; 95%). A favourable bacteriological response was observed for 36/44 (81.8%) loracarbef-treated patients compared with 28/40 (70%) amoxicillin-treated patients (p = 0.2). Adverse events were similar in both groups. Withdrawal of treatment was required in three patients in each group due to gastrointestinal events or rash/allergic exanthema. These data support the conclusion that loracarbef and amoxicillin have comparable efficacy and safety in the treatment of bronchopneumonia and lobar pneumonia caused by susceptible pathogens. However, loracarbef can be administered twice daily, offering the advantage of improved patient compliance. It is also active against beta-lactamase producing organisms.

Loracarbef (LY163892) vs Amoxicillin/Clavulanate in Bacterial Maxillary Sinusitis

Loracarbef (LY 163892), a β-lactam antibiotic (carbacephem), was compared with amoxicillin/ clavulanate potassium in a 10-day, single-blind, randomized parallel trial in the treatment of acute bacterial maxillary sinusitis. Based on posttherapy aspirate and culture, there was a 95.2% bacteriologic cure rate in patients receiving loracarbef (400 mg twice daily) and an 86.7% cure rate in patients receiving amoxicillin/clavulanate (500/125 mg three times daily) ( p = 0.359). Loracarbef was comparable in efficacy to amoxicillin/clavulanate with a more desirable safety profile.

Pharmaceutical properties of loracarbef: the remarkable solution stability of an oral 1-carba-1-dethiacephalosporin antibiotic

Loracarbef is an oral 1-carba-1-dethiacephalosporin antibiotic structurally related to cefaclor. Like many beta-lactam antibiotics, loracarbef exists in several hydrated crystalline forms. The pH-solubility profile curve for loracarbef monohydrate is U-shaped, resembling those of other zwitterionic cephalosporins. Loracarbef was found to be much more stable in solution than cefaclor. For example, in pH 7.4 phosphate buffer, loracarbef was unexpectedly found to be 130-150 times more stable than cefaclor and 10-12 times more stable than cephalexin, depending on the phosphate concentration. The pH-stability profile is U-shaped, similar to that of other zwitterionic cephalosporins, and shows maximum stability at the isoelectric point. At any given pH, loracarbef is more stable in solution than any other therapeutically useful cephalosporin. Acetate, borate, citrate, and especially phosphate buffers have catalytic effects on the rate of loracarbef hydrolysis.

High-performance liquid chromatographic determination of loracarbef, a potential metabolite, cefaclor and cephalexin in human plasma, serum and urine

A high-performance liquid chromatographic (HPLC) method is reported for the determination of a new carbacephem antibiotic, loracarbef, a hydroxylated analogue, and two cephalosporins, cefaclor and cephalexin, in plasma, serum, and urine. The antibiotics are extracted from plasma by means of C18 solid-phase cartridges. Urine samples are diluted with water and directly injected on the HPLC system. The HPLC system utilizes a Supelcosil LC-18-DB (250 mm x 4.6 mm I.D.) reversed-phase column and ultraviolet detection at 265 nm. The limit of quantitation is 0.5 micrograms/ml for each compound. Excellent correlation of plasma concentrations is shown between results determined by HPLC and those obtained by microbiological agar-well diffusion assays. Stability studies of loracarbef in human plasma show the antibiotic to be stable for at least 24 h at room temperature and for at least twelve months at -20 degrees C.

Antimicrobial resistance among respiratory isolates of Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae in the United States

A national surveillance study was conducted to determine trends in antimicrobial resistance patterns among three common causes of community-acquired respiratory tract infections. Fifteen participating U.S. medical centers submitted clinically significant isolates of Haemophilus influenzae, Moraxella (Branhamella) catarrhalis, and Streptococcus pneumoniae to two central laboratories for testing with a group of 12 antimicrobial agents. The majority of isolates were recovered from adult males greater than 50 years old. Overall, 84.1% of 378 M. catarrhalis and 16.5% of 564 H. influenzae (29.5% of type b strains; 15.0% of non-type b strains) produced beta-lactamase and were thus resistant to penicillin, ampicillin, and amoxicillin. Resistance in H. influenzae to other agents was 2.1% to tetracycline, 0.7% to trimethoprim-sulfamethoxazole, 1.1% to cefaclor, and 0.2% to cefuroxime and amoxicillin-clavulanate, while the M. catarrhalis isolates yielded very low MICs of these latter drugs. As demonstrated in prior studies, erythromycin showed little activity against H. influenzae. Of 487 S. pneumoniae isolates, 1 (0.2%) was penicillin resistant, while 3.8% were relatively resistant to penicillin, 4.5% were resistant to trimethoprim-sulfamethoxazole, 2.3% were resistant to tetracycline, 1.2% were resistant to chloramphenicol, and 0.2% were resistant to erythromycin. Overall, the lowest resistance rates for these common bacterial respiratory pathogens were noted with amoxicillin-clavulanate, cefuroxime, and cefaclor.

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.