What type of antibiotic is levofloxacin?

Levofloxacin Classification and Characteristics

Levofloxacin is a fluoroquinolone antibiotic—specifically, it is the L-isomer (optically pure levorotatory form) of the racemic drug ofloxacin, and is classified as a second-generation fluoroquinolone with enhanced activity against Gram-positive organisms, particularly Streptococcus pneumoniae. 1, 2

Chemical and Pharmacological Classification

• Levofloxacin is chemically described as a synthetic, broad-spectrum fluoroquinolone antibacterial agent that is a chiral fluorinated carboxyquinolone 2
• It is the pure (-)-(S)-enantiomer of ofloxacin, making it significantly more active against bacterial pathogens than the R-(+)-ofloxacin isomer 3
• The drug is 97.6% levofloxacin by weight in its commercially formulated hemihydrate form 3

Mechanism of Action

• Levofloxacin exerts 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 1, 2

Antimicrobial Spectrum Classification

• As a second-generation fluoroquinolone, levofloxacin has greater Gram-negative spectrum (including activity against Pseudomonas aeruginosa) compared to first-generation agents, while also demonstrating enhanced Gram-positive activity 1
• Levofloxacin demonstrates significantly enhanced activity against S. pneumoniae compared to ciprofloxacin or ofloxacin, making it one of the "respiratory fluoroquinolones" 1, 4, 5
• The drug maintains broad-spectrum activity against both Gram-positive and Gram-negative bacteria, as well as atypical respiratory pathogens including Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila 1, 6, 7

Clinical Classification Context

• Levofloxacin is specifically categorized alongside moxifloxacin as a fluoroquinolone with "enhanced pneumococcal activity" in clinical guidelines, distinguishing it from ciprofloxacin which lacks adequate pneumococcal coverage 1
• At the time of the 2006 UK guidelines, levofloxacin and moxifloxacin were the only UK-licensed fluoroquinolones with enhanced activity against S. pneumoniae in addition to coverage for Staphylococcus aureus 1
• Current resistance surveillance data shows S. pneumoniae resistance to levofloxacin remains <1% overall in the US 6, 7

Important Distinguishing Features from Other Fluoroquinolones

• Unlike third-generation fluoroquinolones (such as gemifloxacin), levofloxacin has less enhanced pneumococcal activity, though still substantially greater than ciprofloxacin 1
• Unlike fourth-generation fluoroquinolones (such as moxifloxacin), levofloxacin does not have the same degree of anaerobic coverage 1
• Levofloxacin is available in both oral and intravenous formulations with 99% bioavailability, allowing seamless transition between routes without dosage adjustment—a feature not shared by moxifloxacin which only comes in oral formulation in the UK 1, 2, 3