Comparative in vitro antibacterial activities of two new oral cephalosporins, ceftetrame (Ro 19-5247) and cefetamet (Ro 15-8074)

Cefetamet pivoxil clinical pharmacokinetics

Cefetamet pivoxil is an orally absorbed prodrug ester of the microbiologically active cephalosporin, cefetamet. The prodrug ester is completely hydrolysed to the active compound cefetamet on its first pass through the gut wall, the liver or both. Cefetamet is classified as a third generation cephalosporin with excellent activity against streptococci, Enterobacteriaceae, Neisseria and Haemophilus species. It has enhanced stability against beta-lactamases compared with penicillins and first and second generation cephalosporins. The antibacterial spectrum is comparable with that of cefotaxime except for its poor activity against staphylococci. Following a 20-minute zero-order intravenous infusion, cefetamet had a rapid distribution phase followed by a monoexponential decline. The average pharmacokinetic parameters from 152 healthy volunteers were: total body clearance 136 ml/min (8.16 L/h); renal clearance 119 ml/min (7.14 L/h); nonrenal clearance 17 ml/min (1.02 L/h); volume of distribution at steady-state 0.29 L/kg; terminal elimination half-life 2.2 hours; 88% of the dose recovered in the urine. Cefetamet is not extensively bound to plasma proteins. Consequently, these data indicate that cefetamet is predominantly eliminated unchanged by the kidney via glomerular filtration with possibly a minor component of tubular secretion. Cefetamet has a relatively small apparent volume of distribution consistent with that of other beta-lactam antibiotics. Results following ascending intravenous doses of cefetamet in healthy young male volunteers demonstrated that the pharmacokinetics of intravenous cefetamet are independent of the dose. The absolute bioavailability of cefetamet tablets following oral cefetamet pivoxil administration is enhanced by the presence of food. Under fed conditions, 50 to 60% of the final oral dose is absorbed into the systemic circulation. This food effect is observed when cefetamet pivoxil is administered within 1 hour of a meal. Food also produces a slight delay in the time to reach peak plasma concentrations of this drug. Changes in fluid volume intake with cefetamet pivoxil administration have no effect on the bioavailability of this drug. Similar absorption characteristics have been observed for all of the tablet dosage formulations studied during clinical development. The absolute bioavailability of the final syrup dosage formulation was between 38 and 47%. Little improvement in the bioavailability of this preparation has been observed with food. The absorption and disposition of cefetamet in human subpopulations [i.e. children, elderly (< 75 years of age), renal impairment, liver disease and patients taking concomitant drugs] have been studied extensively. Only impaired renal function appears to significantly alter the elimination of this drug.(ABSTRACT TRUNCATED AT 400 WORDS)

Cefetamet pivoxil. A review of its antibacterial activity, pharmacokinetic properties and therapeutic use

Cefetamet pivoxil is an oral third-generation cephalosporin which is hydrolysed to form the active agent, cefetamet. Cefetamet has excellent in vitro activity against the major respiratory pathogens Streptococcus pneumoniae, Haemophilus influenzae, Moraxella (Branhamella) catarrhalis and group A beta-haemolytic streptococci; it is active against beta-lactamase-producing strains of H. influenzae and M. catarrhalis, but has poor activity against penicillin-resistant S. pneumoniae. Cefetamet has marked activity against Neisseria gonorrhoeae and possesses a broad spectrum of activity against Enterobacteriaceae. Both staphylococci and Pseudomonas spp. are resistant to cefetamet. Cefetamet pivoxil has been investigated in the treatment of both upper and lower community-acquired respiratory tract infections and has demonstrated equivalent efficacy to a number of more established agents, namely cefaclor, amoxicillin and cefixime. In patients with group A beta-haemolytic streptococcal pharyngotonsillitis, a 7-day course of cefetamet pivoxil was as effective as a 10-day course of the standard agent, phenoxymethylpenicillin, in this indication. In complicated urinary tract infections, cefetamet pivoxil showed similar efficacy to cefadroxil, cefaclor and cefuroxime axetil. Cefetamet pivoxil was effective in the treatment of otitis media, pneumonia, pharyngotonsillitis and urinary tract infections in children. Preliminary data indicate that single dose cefetamet pivoxil can effectively eradicate N. gonorrhoeae from both men and women. Cefetamet pivoxil has a tolerability profile similar to that of other oral cephalosporins, with gastrointestinal effects being the most commonly reported adverse events. To date, no symptoms of carnitine deficiency have been reported with cefetamet pivoxil. Cefetamet pivoxil offers effective alternative oral therapy for outpatient treatment of community-acquired respiratory tract infections, with the advantage of improved activity against H. influenzae and increased beta-lactamase stability. However, its use in areas with a high incidence of penicillin-resistant S. pneumoniae is likely to be limited. Cefetamet pivoxil is also effective in the treatment of urinary tract infections, although further trials are required to define any comparative advantages over other oral agents.

Effects of cefetamet (Ro 15-8074) on Treponema pallidum and experimental syphilis

Cefetamet pivoxil (Ro 15-8075) is a newly developed, expanded-spectrum cephalosporin that is orally active. In vitro, the active form, cefetamet (Ro 15-8074), at a concentration of 0.05 micrograms/ml killed and lysed Treponema pallidum. Rabbit serum did not diminish its effectiveness. The antibiotic rapidly entered the circulation following intramuscular injection into rabbits, attaining its highest levels of 24 to 37 micrograms/ml within 10 to 30 min. Animals were infected intradermally with T. pallidum and then treated with different doses of cefetamet. Accelerated healing was detected following treatment with 15 and 30 mg/kg of body weight. The antibiotic was also effective in killing organisms that had disseminated to distant tissues. In three separate sets of experiments, rabbits were infected with treponemes and then treated with cefetamet intramuscularly at 1, 15, or 30 mg/kg as follows: (i) after lesions had just become clinically apparent, (ii) after lesions were enlarged and well developed, or (iii) prior to the appearance of clinical lesions. Antibiotic effectiveness was determined by sacrificing the animals 1 week after antibiotic treatment and examining splenic tissue for residual, disseminated treponemes. Cefetamet was treponemicidal in all three situations. Maximum effects occurred when the antibiotic was injected before lesions had become clinically apparent (incubation period). These results suggest that cefetamet pivoxil might be useful for treating syphilitic infections.

Comparative antimicrobial activity of ceftibuten against multiply-resistant microorganisms from Belgium

To study the activity of ceftibuten, we obtained multiply-resistant isolates from approximately 20 hospitals in Belgium. Against Enterobacteriaceae, all of the tested comparative compounds were more active than cefaclor, and ceftibuten and tigemonam were the most active of the agents tested. Ceftibuten MIC50s were less than or equal to 1 microgram/ml for most enteric bacilli species and 85% of strains were susceptible (less than or equal to 8 micrograms/ml). This level of activity compared favorably to that recorded for cefaclor (less than or equal to 8 micrograms/ml), cefetamet (less than or equal to 4 micrograms/ml), and cefteram (less than or equal to 1 microgram/ml), that is, 37%, 69%, and 59%, respectively. Ceftibuten, cefetamet, cefteram, and tigemonam were highly active against isolates of Haemophilus influenzae and Neisseria gonorrhoeae. None of the comparative agents were as active as cefaclor against staphylococcal isolates. Against streptococci, cefteram was the most active, and tigemonam the least active of the agents. The MIC90s of ceftibuten for strains of Streptococcus pneumoniae and Streptococcus pyogenes were 2 micrograms/ml and 0.5 microgram/ml, respectively. Strains of Streptococcus agalactiae were resistant to both ceftibuten and tigemonam; cefaclor and cefteram inhibited 100% of isolates of this species. Strains of Enterococcus faecalis and Pseudomonas aeruginosa were consistently resistant to all of the compounds. Overall, ceftibuten exhibited potent activity against many multiply-resistant clinical isolates.

Antimicrobial activity and stability to beta-lactamase of BMY-28271, a new oral cephalosporin ester

BMY-28271, the acetoxyethyl ester of BMY-28232, 7-[(Z)-2-(2-aminothiazol-4-yl)-2-hydroxyiminoacetamido]-3(Z) -propen-1-yl-3- cephem-4-carboxylic acid, is a new oral cephalosporin. BMY-28232 has a widely expanded spectrum with high activity against gram-positive and gram-negative bacteria. BMY-28232 is far more active than cefixime or cefteram against Staphylococcus aureus and Staphylococcus epidermidis. Against gram-negative bacteria, the activity of BMY-28232 was comparable to or somewhat weaker than that of cefixime or cefteram. BMY-28232 was a poor substrate for various beta-lactamases. Orally administered BMY-28271 had a good therapeutic effect on systemic infections with S. aureus and some gram-negative bacteria in mice. Oral BMY-28271 was efficacious against S. aureus Smith infection: the efficacy of BMY-28271 was 80 to 90 times higher than that of cefixime or cefteram.

In vitro and in vivo antibacterial activities of ME1207, a new oral cephalosporin

ME1207 (pivaloyloxymethyl ester of ME1206) is a new oral cephalosporin. ME1206 is (6R,7R)-7-[(Z)-2-(2-aminothiazol-4-yl)-2-(methoxyimino)- acetamido]-3-[(Z)-2-(4-methylthiazol-5-yl)-ethyl]-cephem-4-carboxy lic acid. The susceptibilities of about 1,600 clinical isolates to ME1206 were determined by the agar dilution method. ME1206 showed a broad spectrum of activity against gram-positive and gram-negative bacteria. ME1206 was more active than cefaclor, T-2525, and cefixime against Staphylococcus aureus and Staphylococcus epidermidis. Against gram-negative bacteria, the activity of ME1206 was comparable with that of T-2525, but ME1206 was less active than cefixime. Against Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria gonorrhoeae, ME1206 had high activity (MIC, less than or equal to 0.05 microgram/ml). ME1206 was stable against various beta-lactamases, except beta-lactamases from Providencia rettgeri, Pseudomonas cepacia, and Escherichia coli W3630 (Rms213). The 50% effective doses of ME1207 after oral administration against systemic infections in mice were comparable with those of T-2588 against gram-negative bacteria and about one-fourth that of T-2588 against Staphylococcus aureus Smith.

World-wide development of antibiotic resistance in pneumococci

Antibiotic-resistant pneumococci, especially penicillin-resistant strains, are being increasingly isolated. Pneumococci with intermediate penicillin-resistance (MIC 0.1-1.0 micrograms/ml) have been reported from many parts of the world over the past two decades, and highly resistant strains (penicillin MICs greater than or equal to 2 micrograms/ml) have also appeared. Infection may be acquired in the hospital or community, and nosocomial outbreaks may occur which require control measures to limit organism spread. Most infections occur in children with diminished host responses. Disease caused by pneumococci with intermediate penicillin-resistance may be treated with high doses of penicillin, but disease caused by highly resistant strains, especially meningitis, may require alternative therapy. Pneumococci resistant to sulfonamides, tetracyclines, erythromycin, lincomycin, clindamycin, chloramphenicol, aminoglycosides and rifampin have also appeared. Strains resistant to all the above-mentioned agents, including all beta-lactam antibiotics tested, have been reported from South Africa and Spain. Alternative therapy for resistant strains may include vancomycin, cefotaxime, cefoperazone, ceftriaxone and imipenem. Pneumococci isolated from sites suggestive of infection, especially blood and cerebrospinal fluid, should be routinely tested for penicillin-susceptibility.