Levofloxacin Classification
Levofloxacin is a second-generation fluoroquinolone antibiotic agent. 1
Classification of Fluoroquinolones
The fluoroquinolones are classified into generations based on their antimicrobial spectrum and chemical modifications:
First Generation
- Nalidixic acid (prototype quinolone approved by FDA in 1964)
- Limited gram-negative coverage
- No significant activity against respiratory pathogens
Second Generation
- Levofloxacin
- Ciprofloxacin
- Ofloxacin
- Norfloxacin
- Characterized by greater gram-negative spectrum with activity against Pseudomonas aeruginosa 1
- Levofloxacin is the L-isomer (optical S-(-) isomer) of the racemic drug ofloxacin 2
Third Generation
- Gemifloxacin
- Characterized by substantially increased activity against Streptococcus pneumoniae while retaining activity against many gram-negative pathogens
- Enhanced activity against respiratory pathogens including Mycoplasma pneumoniae and Chlamydophila pneumoniae 1
Fourth Generation
- Moxifloxacin
- Characterized by increased activity against anaerobes while maintaining gram-positive and gram-negative coverage of third-generation agents
- Excellent activity against mycobacteria including most strains of Mycobacterium tuberculosis 1
Levofloxacin's Antimicrobial Properties
Levofloxacin has a broad spectrum of activity against:
- Gram-positive bacteria
- Gram-negative bacteria
- Atypical respiratory pathogens 3
The mechanism of action involves inhibition of bacterial topoisomerase IV and DNA gyrase (both type II topoisomerases), which are enzymes required for DNA replication, transcription, repair, and recombination 3.
Levofloxacin is approximately twice as potent as ofloxacin, as it is the active isomer of the racemic mixture 4. This increased potency allows for lower dosing while maintaining efficacy.
Clinical Applications
Levofloxacin is FDA-approved for various infections including:
- Community-acquired pneumonia
- Acute bacterial sinusitis
- Complicated urinary tract infections
- Acute pyelonephritis 5
It can be administered in both oral and intravenous formulations, with nearly 100% oral bioavailability, allowing for convenient transition between administration routes 3.
Important Considerations
- Resistance to fluoroquinolones is increasing, and judicious use is recommended to preserve efficacy
- Levofloxacin should be reserved for situations where no safe and effective alternative exists, particularly in pediatric patients 1
- Common adverse effects include gastrointestinal disturbances and central nervous system effects 6
Understanding levofloxacin's classification as a second-generation fluoroquinolone is important for appropriate prescribing decisions, especially when considering antimicrobial spectrum, resistance patterns, and potential adverse effects.