Pharmacokinetics and dose proportionality of cefpimizole in normal humans after intramuscular administration

The pharmacokinetics of cefpimizole (free acid equivalents of cefpimizole sodium), a broad-spectrum cephalosporin antibiotic, were evaluated after intramuscular administration of single doses (dose range, 100 to 1,000 mg) and multiple doses (dose range, 500 to 2,000 mg) given b.i.d. for 6 or 11 days. The kinetics after intramuscular administration correspond to a one-compartment model with first-order input. The apparent volume of distribution of the absorbed dose averaged 18.6 +/- 3.4 (standard deviation) liters for 58 individuals; the absorption-phase and elimination-phase rate constants averaged 2.53 +/- 1.16 h-1 (half-life, 0.27 h) and 0.338 +/- 0.041 h-1 (half-life, 2.05 h), respectively; and the mean residence time was 3.43 +/- 0.43 h. The total body clearance of the absorbed dose after single-dose intramuscular administration was 102 +/- 13 ml/min. The primary route of elimination was renal with 73 to 83% of the administered dose excreted in the urine as unchanged drug. Renal clearance averaged 81 +/- 13 ml/min. Dose proportionality was obtained from area under the plasma curve, concentration maximum in plasma, and cumulative urinary excretion levels. Multiple-dose evaluation of intramuscular administration of cefpimizole indicated no apparent change in the absorption or elimination phases after b.i.d. dosing for 6 or 11 days. The kinetic parameters determined from multiple-dose plasma and urine levels were in close agreement with the same parameters calculated from single-dose results. No apparent accumulation of cefpimizole occurred, and nondetectable levels of drug were observed in the 24-h plasma and 24- to 48-h urine specimen after administration of the last dose. The kinetics of cefpimizole after intramuscular administration were similar to the kinetics obtained after intravenous infusion.