Levofloxacin Classification
Levofloxacin is a fluoroquinolone antibiotic, specifically the L-isomer of the racemic drug ofloxacin. 1
Mechanism of Action
Fluoroquinolones exert their bactericidal activity by binding to bacterial DNA gyrase and topoisomerase IV, which impedes the formation of supercoiled DNA, inhibits the relaxation of supercoiled DNA, and promotes double-strand DNA breakage. 2, 1
Antimicrobial Spectrum
Levofloxacin demonstrates broad-spectrum activity against:
- Gram-positive organisms including Streptococcus pneumoniae (both penicillin-susceptible and penicillin-resistant strains) 2, 3
- Gram-negative organisms including Haemophilus influenzae and Moraxella catarrhalis 2
- Atypical respiratory pathogens including Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila 2, 4
- Mycobacteria including Mycobacterium tuberculosis 2
Comparative Activity Within Fluoroquinolones
Levofloxacin has enhanced activity against Gram-positive organisms compared to ciprofloxacin, particularly against S. pneumoniae, though it is less active than newer fluoroquinolones such as gatifloxacin and moxifloxacin. 2, 3 Ciprofloxacin has an AUC-to-MIC ratio against S. pneumoniae of only 10-20, whereas levofloxacin and other "respiratory fluoroquinolones" achieve the target AUC-to-MIC ratio of approximately 25-30. 2
Cross-resistance has been demonstrated among ciprofloxacin, ofloxacin, and levofloxacin, and is presumably a class effect of fluoroquinolones. 2
Clinical Positioning
Among the fluoroquinolones, levofloxacin, moxifloxacin, and gatifloxacin have the most activity against M. tuberculosis, with levofloxacin being the preferred oral agent for treating drug-resistant tuberculosis based on cumulative experience suggesting a good safety profile with long-term use. 2
Levofloxacin and moxifloxacin are the only currently UK-licensed fluoroquinolones with enhanced activity against S. pneumoniae, in addition to coverage for Staphylococcus aureus. 2