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Pharmacology: Ciprofloxacin has in vitro activity against a wide range of gram-negative and gram-positive organisms, possessing the greatest antibacterial activity of all quinolones. The bactericidal action of ciprofloxacin results from interference with the enzyme DNA gyrase which is needed for the synthesis of bacterial DNA. Ciprofloxacin has been shown to be active against most strains of the following organisms both in vitro and in clinical infections (see Indications/Uses): Gram-Positive: Staphylococcus aureus (including methicillin-susceptible and methicillin-resistant strains), Staphylococcus epidermidis, Streptococcus pneumoniae, Viridans group of Streptococcus.
Gram-Negative: Pseudomonas aeruginosa, Serratia marcescens, Haemophilus influenzae.
Other Organisms: Most strains of Pseudomonas cepacia and some strains of Pseudomonas maltophilia are resistant to ciprofloxacin as are most anaerobic bacteria, including Bacteroides fragilis and Clostridium difficile.
The minimal bactericidal concentration (MBC) generally does not exceed the minimal inhibitory concentration (MIC) by more than a factor of 2. Resistance to ciprofloxacin in vitro usually develops slowly (multiple-step mutation). A plasmid-mediated bacterial resistance does not appear to occur with the fluoroquinolone class of antibiotics; however, parallel resistance is seen with this group of gyrase inhibitors.
There is no cross-over resistance between ciprofloxacin and other antibacterial compounds with different chemical structures, such as â-lactam antibiotics, aminoglycosides, tetracyclines, macrolide and peptide antibiotics as well as sulfonamides, trimethoprim and nitrofuran derivatives because of its special mode of action.
Pharmacodynamics: Clinical Studies: Following therapy with CIPROFLOXACIN Eye Drops 76% of the patients with corneal ulcers and positive bacterial cultures were clinically cured and complete re-epithelialization occurred in about 92% of the ulcers. In 3 and 7 day multicentre clinical trials, 52% of the patients with conjunctivitis and positive conjunctival cultures were clinically cured and 70-80% had all causative pathogens eradicated by the end of treatment.
Pharmacokinetics: Results of a systemic absorption study of CIPROFLOXACIN Eye Drops administered in each eye every two hours while awake for two days followed by every four hours while awake for an additional 5 days showed: the maximum reported plasma concentration of ciprofloxacin was 4.7 ng/mL (some 450-fold less than levels observed following simple 250 mg oral administration). The mean concentration was usually less than 2.5 ng/mL.
Toxicology: Toxicological Properties: Results of research on Ciprofloxacin and related drugs have shown them to cause arthropathy in immature animals of most species tested following oral administration. However, a one-month topical ocular study using immature Beagle dogs did not demonstrate any articular lesions. Acute topical ocular toxicology studies performed in rabbits employing an exaggerated topical ocular exposure to 0.3%, 0.75%, or 1.5% ciprofloxacin ophthalmic solution showed findings that were minimal and transient in nature, confined to the conjunctiva and generally comparable to those effects observed in the untreated control and vehicle control groups.
A subchronic, one-month topical ocular irritation study of 0.3% to 1.5% ciprofloxacin ophthalmic solution did not demonstrate any apparent systemic or ocular toxicity in rabbits.
