[Pharmacokinetics and metabolism of the cephalosporins].

Apart from their antimicrobial activity pattern the cephalosporins differ by their pharmacokinetics. Most cephalosporins have a plasma half life of 30 to 120 minutes. Only ceftriaxon has a half life of about 8 hours, which implicates extended dose intervals. Cephalosporins are excreted renally. Cefoperazone and ceftriaxon, however, are excreted with the bile up to 30%. Cefalotin, cefacetril and cefotaxime are metabolized to a significant degree. Only the main-metabolite of cefotaxime shows mentionable antimicrobial activity. With regard to renal insufficiency (creatinine clearance greater than 5 ml/min) dose reduction is not necessary with cefoperazone and with ceftriaxon because of hepatic excretion and with cefotaxime because of metabolism.