The pharmacokinetics and therapeutic efficacy of fleroxacin and pefloxacin in a rat abscess model.

The penetration, pharmacokinetics and therapeutic efficacy of fleroxacin and pefloxacin were investigated in a rat abscess model. Abscesses were induced by implanting a dialysis tube unit contaminated with Serratia marcescens in the subcutaneous tissue. Simultaneous serum, interstitial fluid (IF) and abscess fluid concentrations of the investigated antibiotics were measured 24 and 96 h after implantation. The concentrations were determined at various time intervals after the last intramuscular administration of each drug (20 mg/kg). Peak fleroxacin and pefloxacin concentrations in the serum of the infected animals were 14.6 +/- 4.7 mg/l and 13 +/- 2.9 mg/l respectively, peak fleroxacin and pefloxacin abscess fluid concentrations after 24 h were 12.3 +/- 2.5 mg/l and 8.9 +/- 2.2 mg/l, respectively (85% and 68% of peak serum concentrations). Abscess fluid concentrations at 96 h were: fleroxacin 4.7 +/- 2.6 mg/l and pefloxacin 4.5 +/- 1.7 mg/l. Both antimicrobials persisted significantly longer in the abscess fluid than in serum. Both drugs failed to sterilize the abscesses following a single administration; however after four consecutive administrations all abscesses became sterile. We conclude that fleroxacin and pefloxacin may be suitable for the therapy of closed space infections caused by susceptible micro-organisms.