Ciprofloxacin Drug Classification
Ciprofloxacin is a second-generation fluoroquinolone antibiotic. 1, 2
Classification Details
Ciprofloxacin belongs to the fluoroquinolone class of antimicrobial agents, which are structurally related to nalidixic acid and enhanced by the addition of 6-fluoro and 7-piperazino substituents. 3
Generational Classification
Second-generation fluoroquinolone: Ciprofloxacin was introduced in 1987 following norfloxacin (1986) and represents the second generation of these agents. 1
Spectrum characteristics: As a second-generation agent, ciprofloxacin has greater Gram-negative spectrum including Pseudomonas aeruginosa activity compared to first-generation agents. 2
Mechanism of Action
Ciprofloxacin exerts bactericidal activity by inhibiting bacterial DNA gyrase (topoisomerase II) and topoisomerase IV, which are essential enzymes required for bacterial DNA replication, transcription, repair, and recombination. 4, 5
- This mechanism differs fundamentally from penicillins, cephalosporins, aminoglycosides, macrolides, and tetracyclines, meaning organisms resistant to those classes may remain susceptible to ciprofloxacin. 4
Antimicrobial Spectrum
Ciprofloxacin demonstrates broad-spectrum activity with particular strength against Gram-negative bacteria:
Gram-negative coverage: Highly active against most Gram-negative enteric bacteria, Pseudomonas aeruginosa, Haemophilus influenzae, and Neisseria gonorrhoeae. 6, 3
Gram-positive coverage: Many Gram-positive bacteria are susceptible or moderately susceptible, including methicillin-susceptible Staphylococcus aureus and Streptococcus pneumoniae (penicillin-susceptible strains). 4, 6
Notable limitation: Ciprofloxacin has inadequate activity against Streptococcus pneumoniae compared to newer fluoroquinolones and should not be first-line for respiratory infections where penicillin-susceptible S. pneumoniae is the primary pathogen. 1, 6
Comparison to Other Fluoroquinolone Generations
Third-generation agents (gemifloxacin): Increased activity against Streptococcus pneumoniae while maintaining Gram-negative coverage. 2
Fourth-generation agents (moxifloxacin): Increased anaerobic activity while maintaining both Gram-positive and Gram-negative coverage. 2
Ciprofloxacin's AUC-to-MIC ratio against S. pneumoniae is only 10-20, whereas the target ratio for fluoroquinolones against this pathogen is approximately 25-30, making newer agents like levofloxacin, gatifloxacin, and moxifloxacin more appropriate for pneumococcal infections. 1