Fleroxacin, like all quinolones, is well absorbed, reaching peak concentrations within 2 h. Interactions with Ca2+ and Al3+ are minimal compared with other quinolones and possibly of little clinical importance. The drug is eliminated via filtration in the kidney. It is therefore sensitive to changes in renal function. Accumulation of drug in the body is minimal, and change from intravenous to oral dosing results in nearly identical serum concentrations. Aside from the modest effect of metals on its absorption, fleroxacin does not interact/compete with substances oxidized in the liver, such as theophylline, and drug interactions are minimal. Its long serum half-life (8-12 h) allows once-a-day dosing. This may be of particular pharmacodynamic advantage when treating infections caused by organisms with relatively high MIC's. This feature, along with its modest drug interactions, indicates that fleroxacin will probably be an important quinolone useful in a variety of clinical settings.