Kurt G. Naber, MD, PhD, Florian M. E. Wagenlehner, MD
Department of Urology, Hospital St. Elisabeth, Straubing, Teaching Hospital of Technical University of Munich, Munich, Germany

Levofloxacin is ideal as a first-line fluoroquinolone for the treatment of urinary tract infections (UTIs) because of its broad antibacterial spectrum and its favourable pharmacokinetics with almost complete bioavailability (interchangeability of intravenous and oral route) and mainly (> 80%) renal excretion of the parent, active drug with a serum half-life allowing standard once daily dosing. For acute uncomplicated UTIs such as acute cystitis, a 3-day course of levofloxacin 250 mg once daily is recommended. For acute uncomplicated pyelonephritis and mild to moderate complicated UTIs, a dose of 250-500 mg once daily for 5-10 days is usually sufficient. In more severe or hospital-aquired UTIs, which are often caused by less susceptible strains, the dose can further be increased up to 750 mg, as there is evidence of good clinical tolerance of levofloxacin.
Because of increasing resistance among uropathogens (especially Escherichia coli) against conventional antimicrobials like ampicillin and trimethoprim-sulfamethoxazole (TMP-SMX), fluoroquinolones are used as first line treatment of both complicated and uncomplicated UTIs. In some areas, however, an increase in resistance of E. coli against fluoroquinolones can also be observed. UTI treatment strategies need to be developed to slow down the emergence of resistance. Reduced consumption of antibiotics, easing of selection pressure by using different antibiotic classes, and appropriate dosing to eradicate the causative, susceptible pathogens and to block the growth of the most resistant, single-step mutants are possible strategies. Pharmacokinetic (PK) and pharmacodynamic (PD) studies especially designed for the treatment of UTIs and tested by appropriate clinical studies are urgently needed.