Pharmacotherapeutic group: S02AA15 Sensory organs. Otologicals. Antiinfectives.
Mechanism of action
As a fluoroquinolone antibacterial agent, the bactericidal action of ciprofloxacin results from the inhibition of both type II topoisomerase (DNA gyrase) and topoisomerase IV, which are required for bacterial DNA replication, transcription, repair and recombination.
PK/PD relationship
No pharmacodynamic relationship has been described for topical administration. With local pharmaceutical forms, the concentration attained in situ are far higher than plasma concentrations.
Mechanism of resistance
In-vitro resistance to ciprofloxacin can be acquired through a stepwise process by target site mutations in both DNA gyrase and topoisomerase IV. The degree of cross-resistance between ciprofloxacin and other fluoroquinolones that results is variable. Single mutations may not result in clinical resistance, but multiple mutations generally result in clinical resistance to many or all active substances within the class.
Impermeability and/or active substance efflux pump mechanisms of resistance may have a variable effect on susceptibility to fluoroquinolones, which depends on the physiochemical properties of the various active substances within the class and the affinity of transport systems for each active substance. All in-vitro mechanisms of resistance are commonly observed in clinical isolates. Resistance mechanisms that inactivate other antibiotics such as permeation barriers (common in Pseudomonas aeruginosa) and efflux mechanisms may affect susceptibility to ciprofloxacin.
Plasmid-mediated resistance encoded by qnr-genes has been reported.
Breakpoints
For most topical agents there are limited pharmacological data and no data relating treatment to outcome. For this reason EUCAST proposes that epidemiological cut-off values (ECOFFs) are used to indicate susceptibility to topical agents.
Epidemiological cut-off values according to EUCAST. ECOFF ≤ mg/ml
- Enterobacteriaceae | 0.125 mg/l |
- Staphylococcus spp. | 1 mg/l |
- Pseudomonas aeruginosa | 0.5 mg/l |
Prevalence of resistance may vary according to geographical zone and weather for the selected microorganisms. Local information on resistance should be available, particularly in the case of serious infections. This information only provides an approximate orientation as to the probability of the microorganism being sensitive to this antibiotic.
Based on present data the following table represents susceptibility of ciprofloxacin to the leading pathogens in the approved indication.
SPECIES FOR WHICH ACQUIRED RESISTANCE MAY BE A PROBLEM |
Aerobic Gram positive micro-organisms Staphylococcus aureus |
Aerobic Gram negative micro-organisms Pseudomonas aeruginosa |
NB: With local pharmaceutical forms, the concentrations attained in situ are far higher than plasma concentrations. Some doubts remain as to the kinetics of concentrations in situ, the local physical and chemical conditions which may modify the activity of the antibiotic and the stability of the product in situ.