Cephalosporins plasma protein binding

Cephalosporin Generation Route of Administration Add- Resistant Plasma Protein Binding (th) p-Lactamase Resistance Spectrum Activity Antipseudo- monal Activity... 

Ceftiofur and its active metabolite desfuroylceftiofur distribute differently to the other cephalosporins because of their high degree of protein binding. Reversible covalent bonding with plasma and hssue proteins produces lower than expected free concentrations of ceftiofur and desfuroylceftiofur following the administration of clinically effective doses. Tissue chamber studies have shown that concentrations of parent drug and active metabolite are higher in infected than in normal tissues. 

The penicillins and cephalosporins ((3-lactam antibiotics) are weak organic acids that, due to their low pfCa values, are predominantly ionized in the blood plasma. Binding of (3-lactam antibiotics to plasma proteins (albumin) differs between individual penicillins (from 16-22% for ampicillin to over 80% for cloxacillin and nafcillin) and individual cephalosporins (from 15-20% for cephalexin and cefadroxil to over 80% for cefazolin, cefoperazone and ceftriaxone). The consequence of extensive protein binding on clinical efficacy of (3-lactam antibiotics is incompletely understood, apart from decreasing the availability of the drug (unbound fraction) for extravascular distribution. Because of their high degree of ionization in the plasma and consequently relatively low solubility in lipid, the extravascular distribution of (3-lactam... 

Figure 7.10 Bacterial cell wall synthesis. 1) Alanine molecules are added to a carbohydrate tripeptide to form a "T" shaped cell wall precursor. This reaction is inhibited by D-cycloserine. 2) The precursor is transported across the plasma membrane by a carrier. Vancomycin inhibits the transport process. 3) The transporter is recycled to the inside of the cell to carry other precursors. Bacitracin inhibits this step. 4) The precursor is linked to the existing cell wall structure by transpeptidase. Penicillins, cephalosporins, imipenem and aztreonam inhibit the transpeptidase. Transpeptidase is one of several penicillin binding proteins and is not the only site of penicillin action.

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