Moxifloxacin, a new antibiotic designed to treat community-acquired respiratory tract infections: a review of microbiologic and pharmacokinetic-pharmacodynamic characteristics.

Moxifloxacin (BAY 12-8039) is a new 8-methoxy-fluoroquinolone antibacterial agent. The minimum inhibitory concentration for 90% of organisms (MIC90) is less than 0.25 mg/L for commonly isolated community-acquired respiratory tract pathogens including penicillin-susceptible and -resistant Streptococcus pneumoniae, Haemophilus sp, and Moraxella catarrhalis, and less than 1.0 mg/L for atypical pathogens such as Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella pneumophila. To date, emergence of resistance to moxifloxacin has been uncommon, including selection of resistance under experimental conditions (methicillin-sensitive Staphylococcus aureus, S. pneumoniae). A postantibiotic effect is observed for both gram-positive and gram-negative bacteria. Human pharmacokinetics in healthy volunteers after a single 400-mg oral dose were mean maximum concentration (Cmax) 3.2 mg/L, area under the curve (AUC) 37 mg x hour/L, and terminal elimination half-life 12.0 hours. At steady-state, Cmax and AUC were approximately 4.5 mg/L and 48 mg x hour/L, respectively. Because of a balanced system of excretion, no dosage adjustments are required in patients with renal or hepatic impairment. Moxifloxacin also has excellent penetration into upper and lower respiratory tissues. Laboratory pharmacodynamic models suggest that MIC and AUC values predict therapeutic response. Notably, the drug can be administered once/day and is not associated with drug interactions secondary to altered hepatic metabolism. In addition, since its metabolism does not involve the cytochrome P450 system, many common drug interactions are absent. The agent is being investigated in clinical trials and shows promise as a safe and effective once-daily treatment of respiratory infections. In addition, its chemical structure and pharmacokinetic and pharmacodynamic properties indicate that it has enhanced potential to minimize emergence of bacterial resistance, which should make it an excellent choice for treating respiratory tract infections now and in the future.