[Comparative pharmacokinetics of moxalactam and other cephalosporins].

A comparative study of the pharmacokinetics of eleven cephalosporins, given in rapid intravenous injections and studied under identical conditions (sampling regimens, assays by high performance liquid chromatography, statistical analyses), is reported. The very low diffusibility of cephalosporins throughout the body typifies this family of antibiotics. Apparent volumes of distribution vary little from the mean volume which is 0.30 liter per kg body weight. Conversely, apparent elimination half-lifes show significant differences, with values ranging from 0.52 h (cephalotin) and 0.75 h (cefotaxim) to 2.74 h (Moxalactam) and 3.07 h (cefazolin). The consequences of the pharmacokinetic differences between cefotaxim and Moxalactam are exemplified by the comparison of dosage regimens capable of generating and maintaining equivalent concentrations in the various body fluids. Table I shows the main parameters which typify the pharmacokinetic patterns of eleven cephalosporins given intravenously (in young, healthy, adults). The relative values of renal clearance and total clearance demonstrate the part played by extrarenal elimination: metabolization for cephalotin, cefapirin and cefotaxim, and biliary excretion which may be inconsiderable, as is usually the case, or predominant for cefoperazone. Compartmental analysis of plasmatic data provides unequivocal confirmation of open pharmacokinetic models with three compartments whose equations, of the type O plasmatic = Ae-gamma t + Be-gamma t + Ce-gamma t, are shown in Table III.