Dicloxacillin and cloxacillin: Pharmacokinetics in healthy and hemodialysis subjects

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Abstract
Differences in the elimination, distribution, and absorption of dicloxacillin and cloxacillin were studied in a group of healthy individuals with the use of a 2-compartment model. In patients on chronic intermittent hemodialysis, only dicloxacillin was investigated and the results were compared with data obtained in earlier studies on cloxacillin and flucloxacillin. In healthy volunteers the bioavailability after oral administration of 2 gm dicloxacillin or 2 gm cloxacillin amounted to 48.8% and 36.9% of the dose, respectively, when calculated from the area under the serum concentration-time curve, and to 74.1% and 48.5%, respectively, when calculated from the urinary excretion. Individual variation in bioavailability after oral administration was slightly lower for dicloxacillin than for cloxacillin. The higher serum concentrations of dicloxacillin, as compared with cloxacillin, are also attributable to slower (renal) elimination (TV½: 42 and 33 min, respectively). Analysis of serum concentrations after intravenous administration of 1 and 2 gm dicloxacillin to healthy subjects revealed concentration-dependent kinetics with respect to renal elimination. In hemodialysis patients the elimination rate of dicloxacillin (P½: 129 min) corresponds with the extrarenal elimination rate in healthy subjects. The bioavailability after oral administration of 1 gm in patients is good (75.9% of the dose).