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±4·7mg/l and 13±2·9mg/l respectively, peak fleroxacin and pefloxacin abscess fluid concentrations after 24 h were 12·3±2·5mg/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.