Fluoroquinolones commonly end with suffix “-floxacin”, for example ciprofloxacin, levofloxacin, norfloxacin, ofloxacin, sparfloxacin, moxifloxacin, and gatifloxacin. Drugs of this class that do not end with "-floxacin", include enoxacin and nalidixic acid.
Fluoroquinolones inhibit topoisomerase II (a.k.a. DNA gyrase) and IV enzymes. These enzymes cut both strands of the DNA helix in order to unwind DNA tangles and supercoils which is necessary for proper DNA replication. Resistance to these drugs can be due to mutations in these bacterial enzymes, plasmid-encoded efflux pumps, or changes in cell wall permeability.
Unlike bacteriostatic agents, which simply stop bacteria from reproducing, bactericidal agents actually cause bacterial cell death.
These drugs are broad-spectrum antibiotics that play an important role in the treatment of serious bacterial infections, especially against gram negative rod infections. It should be noted that newer generation fluoroquinolones have improved, but have limited gram-positive coverage.
Fluoroquinolones are effective in the treatment of pneumonia. In fact, levofloxacin, gemifloxacin, and moxifloxacin are referred to as the “respiratory fluoroquinolones” for this reason. These antibiotics are also effective in cases of atypical pneumonia caused by Legionella, Chlamydophila pneumoniae, and Mycoplasma.
Bacterial gastroenteritis caused by organisms such as Campylobacter jejuni, Salmonella, Shigella, Yersinia, and non-cholera Vibrio species can be treated with fluoroquinolones.
Fluoroquinolones like ciprofloxacin are a commonly prescribed antibiotic for urinary tract infections (UTI) in females. Note that fluoroquinolones are now second-line treatment for UTIs (after nitrofurantoin, trimethoprim-sulfamethoxazole, and fosfomycin) due to increasing bacterial resistance.
Genital infections caused by Neisseria gonorrhoeae, Chlamydia trachomatis, and Ureaplasma urealyticum are all amenable to treatment with fluoroquinolones.
Levofloxacin is a powerful fluoroquinolone used to treat multiple infections such as community-acquired pneumonia, acute bacterial rhinosinusitis, chronic prostatitis, and acute pyelonephritis. It is also used as postexposure prophylaxis for anthrax caused by Bacillus anthracis.
Ciprofloxacin is a second generation fluoroquinolone antibiotic that is used to treat a number of infections including osteomyelitis, gastroenteritis, malignant otitis externa, respiratory tract infections, and skin infections. This drug is considered a P450 inhibitor and can result in increased plasma concentrations of other drugs metabolized by this hepatic enzyme complex.
Pseudomonas aeruginosa is a gram-negative, aerobic bacillus that has been increasingly recognized as an opportunistic human pathogen. It can cause a variety of infections including osteomyelitis (especially in burn patients), endocarditis, pneumonia, and UTIs. Ciprofloxacin and levofloxacin both have efficacy against Pseudomonas.
Metals such as magnesium (Mg2+), calcium (Ca2+), iron (Fe2+, Fe3+), and aluminum (Al3+) should be avoided when taking fluoroquinolones. These elemental ions may reduce absorption of the antibiotic. They are commonly found in dietary supplements, antacids, or prescribed for certain medical conditions (e.g. iron tablets for anemia).
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