Cephalosporins

Excerpt

The cephalosporins are a family of bactericidal antibiotics structurally related to penicillin which were first derived from the fungus, Cephalosporum acremonium. Their basic structure is similar to penicillin with a thiazolidine and beta-lactam ring, which has a variable side chain. Cephalosporins bind to the penicillin-binding proteins on bacteria and inhibit synthesis of the bacterial cell wall, causing cell lysis particularly in rapidly growing organisms. Their differences in activity relate to the range of penicillin-binding proteins that they inhibit. They have a broader activity than the standard penicillins, but are also sensitive to some extent to beta-lactamase. Five generations of cephalosporins have been developed with varying antibacterial activity. Cephalosporins are indicated for infections with susceptible organisms of various tissues and organs. Cephalosporins have variable oral absorption and many must be given parenterally. The oral preparations are used largely for mild and moderate infections; the parenteral forms for more severe infections and sepsis. In the lists below, formulations that are available in oral and parenteral forms are shown separately. Some of these formulations have been discontinued and are no longer available in the United States.

First generation cephalosporins include cefadroxil, cefazolin, cephalexin, and cephradine, and these are active against many gram-positive cocci, including penicillinase-producing Staphylococcus aureus.

Second generation cephalosporins include cefaclor, cefoxitin, cefprozil, cefonicid, and cefuroxime; these have broader antibacterial activity, and additional sensitive organisms including Citrobacter, Enterobacter, Haemophilus influenzae, Neisseria and Serratia species.