Is Levaquin a Quinolone?
Yes, Levaquin (levofloxacin) is definitively a fluoroquinolone antibiotic—specifically, a second-generation fluoroquinolone that is the L-isomer of the racemic drug ofloxacin. 1
Drug Classification
Levofloxacin belongs to the fluoroquinolone class of antibacterial agents, characterized by a common core dual-ring structure with fluorination that distinguishes it from earlier quinolones like nalidixic acid. 2
Chemical structure: Levofloxacin is the optically pure levorotatory (L-) isomer of ofloxacin, making it 97.6% pure levofloxacin by weight in its commercially formulated hemihydrate form. 3, 4
Generational classification: It is classified as a second-generation fluoroquinolone with enhanced Gram-negative spectrum including Pseudomonas aeruginosa activity, though it has improved activity against Streptococcus pneumoniae compared to ciprofloxacin or ofloxacin. 2, 5, 3
Mechanism of Action
Levofloxacin works by inhibiting bacterial DNA gyrase and topoisomerase IV, both type II topoisomerases essential for DNA replication, transcription, repair, and recombination. 1
The antibacterial activity of ofloxacin resides primarily in the L-isomer (levofloxacin), making it significantly more active against bacterial pathogens than the R-(+)-ofloxacin enantiomer. 1, 4
This mechanism of action differs fundamentally from aminoglycosides, macrolides, and β-lactam antibiotics, potentially allowing activity against bacteria resistant to these other antimicrobial classes. 1
Clinical Context
Fluoroquinolones like levofloxacin should be reserved for situations where no safe and effective alternative exists, due to significant adverse effects including tendinopathy, tendon rupture, and concerns about promoting antimicrobial resistance. 2, 5, 1
The FDA has approved levofloxacin for specific indications including complicated urinary tract infections, pyelonephritis, community-acquired pneumonia, nosocomial pneumonia, acute bacterial sinusitis, and postexposure treatment for inhalation anthrax. 1, 6
Cross-resistance exists between levofloxacin and other fluoroquinolones (ciprofloxacin, ofloxacin), though some microorganisms resistant to other fluoroquinolones may remain susceptible to levofloxacin. 7, 1