A comparison of side effects of levofloxacin to other agents concerning the ecological and microbiological effects on normal human flora.

The safety of levofloxacin was compared to that of non-fluoroquinolone alternatives used for respiratory tract infections. Results from five randomised controlled trials revealed that the incidence of any adverse events possibly associated with levofloxacin ranged from 5.8% to 22.7%, whereas that of comparators (ceftriaxone, cefuroxime axetil, clarithromycin and amoxicillin-clavulanic acid) ranged from 8.5% to 39.3%. The rate of adverse drug reactions (ADRs) was lower for levofloxacin in all trials. The most common adverse events for all agents tended to be gastrointestinal in nature. Levofloxacin was associated with a mild effect on the normal microflora, reaching a maximum at four days of therapy, with complete recovery being achieved by seven days post-therapy. No colonisation with resistant strains was observed during the period of levofloxacin therapy. Amoxicillin-clavulanic acid administration selected for resistant strains of Enterobacteriaceae, and ampicillin administration was associated with both resistant strains of Enterobacteriacae as well as Candida spp. Ceftriaxone selected resistant strains of Clostridium difficile and Candida spp. Thus, microflora effects favoured levofloxacin over all of the agents tested, including macrolides and tetracyclines. These results confirm that the ecological impact of levofloxacin is markedly less than that associated with non-fluoroquinolone comparators. Copyright 2001 S. Karger AG, Basel