β-lactams: cephalosporins

β-lactams: cephalosporins

Cephalosporins are chemically related to penicillins and are bactericidal. Like penicillins, they inhibit the transpeptidation of peptidoglycans. Cephalosporins are usually resistant to penicillinases.

First (cefazolin, cephalexin) and second (cefuroxime, cefotetan) generation cephalosporins are targeted against Gram-positive bacteria such as Streptococci and Staphylococci. The third generation (ceftriaxone, cefotaxime,

and ceftazidime) drugs are more effective against Gram-negative rods. However, they are not sensitive to β-lactamases.

Like penicillins, cephalosporins are mainly excreted via the kidneys. Their absorption is low. The adverse effects profile is similar to that of penicillins: allergic reactions and in high doses neurotoxicity and nephrotoxicity. Cephalosporins are used against skin and soft tissue infections with S. aureus or pyogenes and infections with Klebsiella and Enterobacter.

Population pharmacokinetic parameters for cefuroxime:

Clearance: Cl= 0.94 * creatinine Cl + 0.28 ml/min/kg

Volume of distribution: Vd= 0.20 L/kg

Half-life: t1/2= 1,7 h

1

Third generation cephalosporins are mostly resistant to B-lactamases. 

2

Cephalosporins inhibit the transglycosylation of peptidoglycans.

3

   Cephalosporins inhibit penicillin binding proteins.