Second-generation agents cephalosporins

Cefmetazole (78) is a cephamycin-inspired cephalosporin differing from the mainstream compounds in having an aliphatic amide moiety attached to C-7. Its antibacterial spectrum is similar to the second generation agent cefoxitin. The synthesis starts with 7-aminocephalosporan-... 

Cephalexin, cefaclor, cefprozil, cefadroxil, ceftibuten, and loracarbef are well absorbed from the Gl tract. Cephalosporins are widely distributed to most tissues and fluids. First and second generation agents do not readily enter cerebrospinal fluid (CSF), except cefuroxime, even when meninges are inflamed. Third generation compounds readily diffuse into the CSF of patients with inflamed meninges. However, CSF levels of cefoperazone are relatively low. Most cephalosporins and metabolites are primarily excreted renally. 

This prototype second-generation parenteral cephalosporin has a longer half-life than similar agents. It crosses the blood-brain barrier and can be used for community-acquired bronchitis or pneumonia in the elderly and for patients who are immunocompromised. 

In lower UTI it is essential to choose an agent that achieves a high concentration in urine, e.g. nitrofurantoin or norfloxacin. In a patient with fever, an upper UTI can be expected (pyelonephritis bacteremia) and therefore an agent with adequate concentrations in blood and urine should be given, e.g. the second generation cephalosporin cefurox-ime. When urosepsis develops (high fever, chills... 

After a 1-g intravenous infusion, serum levels are 75-125 mcg/mL for most second-generation cephalosporins. Intramuscular administration is painful and should be avoided. Doses and dosing intervals vary depending on the specific agent (Table 43-2). There are marked differences in half-life, protein binding, and interval between doses. All are renally cleared and require dosage adjustment in renal failure. 

Cephalosporins are semisynthetic antibiotics obtained from the fungus Cephalo-sporium. These bactericidal agents act in a similar way to that of penicillins. There are different types of cephalosporins available first-generation (cefazolin, cefadroxil) second-generation (cefuroxime, cefaclor) third-generation (cefotaxime, cefoperazone) and fourth-generation (cefpirome). 

Second-generation cephalosporins are not as well absorbed orally as the first-generation cephalosporins, have a greater incidence of gastrointestinal adverse effects, and are more expensive than first-generation agents - thus they should only be used where specifically indicated. 

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 l-2 hours. 

Second-generation cephalosporins generally have been displaced by third-generation agents. The oral second-generation cephalosporins can be used to treat respiratory tract infections, although they are inferior to amoxiciUin for treatment of peniciUin-resistant S. pneumoniae pneumonia and otitis media. Cefoxitin and cefotetan both are effective in situations where facultative gramnegative bacteria and anaerobes are involved e.g., intra-abdominal infections, pelvic inflammatory disease, and diabetic foot infection). 

The cephalosporins are classified as first-, second-or third-generation agents. They differ in terms of antibacterial spectmm, stability to bacterial P-lactamases and... 

The third-generation agents display a broader spectmm of antibacterial activity compared to the first- and second-generation cephalosporins. Although these agents display... 

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