Secondgeneration Cephalosporins

Second-generation cephalosporins have a broader spectrum than first-generation agents and are active against Enterobacter spp., indole-positive Proteus spp., and Klebsiella spp. Their serum half-lives are generally ~1—2 hours.

Cefoxitin is resistant to some ¡5-lactamases produced by gram-negative rods. This antibiotic is less active than the first-generation cephalosporins against gram-positive bacteria, but is more active against anaerobes, especially B. fragilis. Cefoxitin's special role is for treatment of certain anaerobic and mixed aerobic-anaerobic infections, such as pelvic inflammatory disease and lung abscess.

Cefaclor's concentration in plasma after oral administration is ~50% of that achieved after an equivalent oral dose of cephalexin. However, cefaclor is more active against H. influenzae and Moraxella catarrhalis, although some ¡ -lactamase-producing strains may be resistant. Loracarbef is similar in activity to cefaclor, which is more stable against some ¡ -lactamases.

Cefuroxime is similar to loracarbef with broader gram-negative activity against some Cit-robacter and Enterobacter spp. Unlike cefoxitin, cefmetazole, and cefotetan, cefuroxime lacks activity against B. fragilis. The drug can be given every 8 hours. Concentrations in CSF are ~10% of those in plasma; the drug is effective (but inferior to ceftriaxone) for treatment of meningitis owing to H. influenzae (including strains resistant to ampicillin), N. meningitidis, and S. pneumoniae.

Cefuroxime axetil is the 1-acetyloxyethyl ester of cefuroxime. Between 30% and 50% of an oral dose is absorbed and then hydrolyzed to cefuroxime; resulting concentrations in plasma are variable.

Cefotetan, like cefoxitin, has good activity against B. fragilis and several other species of Bacteroides and is slightly more active than cefoxitin against gram-negative aerobes. Hypopro-thrombinemia and inhibition of vitamin K activation with bleeding have occurred in malnourished patients receiving cefotetan; this is preventable if vitamin K is also administered.

Cefprozil is an orally administered agent that is more active than first-generation cephalosporins against penicillin-sensitive streptococci, E. coli, P. mirabilis, Klebsiella spp., and Citrobacter spp.

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