Cefpodoxime is a broad-spectrum cephalosporin with useful activity against a relatively wide range of Grampositive and Gram-negative bacteria. It is also resistant to many jS-lactamases. Its spectrum of activity includes S. pneumoniae, Streptococcus pyogenes, S. aureus, H. influenzae, M. catarrhalis, and Neisseria spp. Cefpodoxime is also active against members of the Enterobacteriaceae family, including E. coli, K. pneumoniae, and P. mirabilis. It thus finds use in the treatment of upper and lower respiratory infections, such as pharyngitis, bronchitis, otitis media, and community-acquired pneumonia. It is also useful for the treatment of uncomplicated gonorrhea.
Cefixime (Suprax) is the first orally active, third-generation cephalosporin that is not an ester prodrug to be approved for therapy in the United States. Oral bioavailability is surprisingly high, ranging from 40% to 50%. Facilitated transport of cefixime across intestinal brush border membranes involving the carrier system for dipeptides may explain its surprisingly good oral absorption.91 This result was not expected because cefixime lacks the ionizable a-amino group present in dipeptides and jS-lactams previously known to be transported by the carrier system.51,91
Cefixime is a broad-spectrum cephalosporin that is resistant to many jS-lactamases. It is particularly effective against Gram-negative bacilli, including E. coli, Klebsiella spp., P. mirabilis, indole-positive Proteus, Providencia, and some Citrobacter spp. Most Pseudomonas, Enterobacter, and Bacteroides spp. are resistant. It also has useful activity against streptococci, gonococci, H. influenzae, and M. ca-tarrhalis. It is much less active against S. aureus. Cefixime is used for the treatment of various respiratory tract infections (e.g., acute bronchitis, pharyngitis, and tonsillitis) and otitis media. It is also used to treat uncomplicated urinary tract infections and gonorrhea caused by jS-lactamase-producing bacterial strains.
The comparatively long half-life of cefixime (ti/2 is 3-4 hours) allows it to be administered on a twice-a-day schedule. Renal tubular reabsorption and a relatively high fraction of plasma protein binding (—65%) contribute to the long half-life. It is provided in two-oral dosage forms: 200-or 400-mg tablets and a powder for the preparation of an aqueous suspension.
Cefotaxime Sodium, Sterile
Cefotaxime (Claforan) was the first third-generation cephalosporin to be introduced. It possesses excellent broad-spectrum activity against Gram-positive and Gramnegative aerobic and anaerobic bacteria. It is more active than moxalactam against Gram-positive organisms. Many jS-lactamase-producing bacterial strains are sensitive to cefotaxime, including N. gonorrhoeae, Klebsiella spp., H. influenzae, S. aureus, and E. cloacae. Some, but not all, Pseudomonas strains are sensitive. Enterococci and Listeria monocytogenes are resistant.
The syn-isomer of cefotaxime is significantly more active than the anti-isomer against jS-lactamase-producing bacteria. This potency difference is, in part, because of greater resistance of the syn-isomer to the action of jS-lactamases.78 The higher affinity of the syn-isomer for PBPs, however, may also be a factor.92
Cefotaxime is metabolized in part to the less active de-sacetyl metabolite. Approximately 20% of the metabolite and 25% of the parent drug are excreted in the urine. The parent drug reaches the cerebrospinal fluid in sufficient concentration to be effective in the treatment of meningitis. Solutions of cefotaxime sodium should be used within 24 hours. If stored, they should be refrigerated. Refrigerated solutions maintain potency up to 10 days.
Ceftizoxime Sodium, Sterile
Ceftizoxime (Cefizox) is a third-generation cephalosporin that was introduced in 1984. This jS-lactamase-resistant agent exhibits excellent activity against the Enterobacteriaceae, especially E. coli, K. pneumoniae, E. cloacae, Enterobacter aerogenes, indole-positive and indole-negative Proteus spp., and S. marcescens. Ceftizoxime is claimed to be more active than cefoxitin against B. fragilis. It is also very active against Gram-positive bacteria. Its activity against P. aeruginosa is somewhat variable and lower than that of either cefotaxime or cefoperazone.
Ceftizoxime is not metabolized in vivo. It is excreted largely unchanged in the urine. Adequate levels of the drug are achieved in the cerebrospinal fluid for the treatment of Gram-negative or Gram-positive bacterial meningitis. It must be administered on a thrice-daily dosing schedule because of its relatively short half-life. Ceftizoxime sodium is very stable in the dry state. Solutions maintain potency for up to 24 hours at room temperature and 10 days when refrigerated.
Ceftriaxone Disodium, Sterile
Ceftriaxone (Rocephin) is a jS-lactamase-resistant cephalosporin with an extremely long serum half-life. Once-daily dosing suffices for most indications. Two factors contribute to the prolonged duration of action of ceftriaxone: high protein binding in the plasma and slow urinary excretion. Ceftriaxone is excreted in both the bile and the urine. Its urinary excretion is not affected by probenecid. Despite its comparatively low volume of distribution, it reaches the cerebrospinal fluid in concentrations that are effective in meningitis. Nonlinear pharmacokinetics are observed.
Ceftriaxone contains a highly acidic heterocyclic system on the 3-thiomethyl group. This unusual dioxotriazine ring system is believed to confer the unique pharmacokinetic properties of this agent. Ceftriaxone has been associated with sonographically detected "sludge," or pseudolithiasis, in the gallbladder and common bile duct.93 Symptoms of cholecystitis may occur in susceptible patients, especially those on prolonged or high-dose ceftriaxone therapy. The culprit has been identified as the calcium chelate.
Ceftriaxone exhibits excellent broad-spectrum antibacterial activity against both Gram-positive and Gram-negative organisms. It is highly resistant to most chromosomally and plasmid-mediated S-lactamases. The activity of ceftriaxone against Enterobacter, Citrobacter, Serratia, indole-positive Proteus, and Pseudomonas spp. is particularly impressive. It is also effective in the treatment of ampicillin-resistant gonorrhea and H. influenzae infections but generally less active than cefotaxime against Gram-positive bacteria and B. fragilis.
Solutions of ceftriaxone sodium should be used within 24 hours. They may be stored up to 10 days if refrigerated.
Ceftazidime Sodium, Sterile
Ceftazidime (Fortaz, Tazidime) is a jS-lactamase-resistant third-generation cephalosporin that is noted for its an-tipseudomonal activity. It is active against some strains of P. aeruginosa that are resistant to cefoperazone and ceftriaxone. Ceftazidime is also highly effective against j-lacta-mase-producing strains of the Enterobacteriaceae family. It is generally less active than cefotaxime against Gram-positive bacteria and B. fragilis.
The structure of ceftazidime contains two noteworthy features: (a) a 2-methylpropionicoxaminoacyl group that confers jS-lactamase resistance and, possibly, increased permeability through the porin channels of the cell envelope and (b) a pyridinium group at the 3-position that confers zwitterionic properties on the molecule.
Ceftazidime is administered parenterally 2 or 3 times daily, depending on the severity of the infection. Its serum half-life is about 1.8 hours. It has been used effectively for the treatment of meningitis caused by H. influenzae and N. meningitidis.
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