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Fluoroquinolones, Mechanism of Action (MOA):, Metabolism and Excretion:,…
Fluoroquinolones
Fluoroquinolones are a class of broad-spectrum
antibiotics that have become a cornerstone in the
treatment of various bacterial infections.
Fluoroquinolones were a significant advancement
over the earlier quinolones (such as nalidixic acid)
due to their enhanced activity, broader spectrum,
and superior pharmacokinetics.
They have been widely adopted for their efficacy in
treating infections caused by gram-negative and
gram-positive bacteria, including some resistant organisms.
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Distribution:
They penetrate well into most tissues and fluids,
including the lungs, bones, prostate, and kidneys.
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First Generation:
Includes norfloxacin.
It is primarily effective against gram-negative
bacteria, particularly in urinary tract infections.
Second Generation:
Includes ciprofloxacin and ofloxacin.
These agents have expanded activity against
gram-negative bacteria, including Pseudomonas,
and some activity against gram-positive organisms.
Third Generation:
Includes levofloxacin and gatifloxacin.
These agents show increased activity against
gram-positive bacteria, such as Streptococcus
pneumoniae, while maintaining strong gram-negative coverage.
Fourth Generation:
Includes moxifloxacin and gemifloxacin.
These drugs have the broadest spectrum of
activity, covering both gram-positive and gram-
negative bacteria, as well as anaerobes.
Spectrum of Activity:
Fluoroquinolones are broad-spectrum antibiotics, effective against:
Gram-negative bacteria: Including Escherichia coli,
Klebsiella, Enterobacter, Proteus, Pseudomonas aeruginosa, and Neisseria gonorrhoeae.
Gram-positive bacteria: Third and fourth-generation agents are especially effective against Streptococcus pneumoniae, Staphylococcus aureus (non-MRSA), and Enterococcus.
Atypical bacteria: Such as Mycoplasma pneumoniae, Legionella pneumophila, and Chlamydia pneumoniae.
Anaerobes: Fourth-generation agents like moxifloxacin have activity against anaerobic bacteria, making them useful in treating mixed infections.
Clinical Applications:
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Urinary Tract Infections (UTIs): Fluoroquinolones are commonly used for complicated and uncomplicated UTIs, with norfloxacin often used for cystitis and ciprofloxacin for pyelonephritis.
Respiratory Tract Infections: Third-generation fluoroquinolones, particularly levofloxacin and moxifloxacin, are effective in treating community-acquired pneumonia, bronchitis, and sinusitis.
Gastrointestinal Infections: Ciprofloxacin is frequently used to treat traveler’s diarrhea, shigellosis, and salmonellosis.
Sexually Transmitted Infections (STIs): Ciprofloxacin and ofloxacin were once first-line treatments for gonorrhea but are less commonly used today due to resistance.
Anthrax Prophylaxis and Treatment: Ciprofloxacin is the drug of choice for post-exposure prophylaxis and treatment of anthrax.
Bone and Joint Infections: Fluoroquinolones have good bone penetration and are used to treat osteomyelitis caused by susceptible organisms.
Skin and Soft Tissue Infections: These agents are used in serious skin infections, particularly when caused by resistant gram-negative organisms.
Multidrug-resistant Tuberculosis (MDR-TB): Levofloxacin and moxifloxacin are used as second-line agents in the treatment of MDR-TB.
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Drug Interactions:
Antacids and Supplements: Fluoroquinolone absorption is reduced by antacids or supplements containing calcium, magnesium, aluminum, or iron.
Theophylline: Ciprofloxacin increases the plasma concentration of theophylline, potentially leading to toxicity.
NSAIDs: Concomitant use of NSAIDs with fluoroquinolones increases the risk of CNS toxicity, including seizures.
Current Challenges:
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Increasing Resistance: Overuse and misuse have led to increasing resistance among common pathogens, making some infections harder to treat.
Safety Concerns: Due to the risk of serious adverse effects (e.g., tendon rupture, neuropathy), many regulatory agencies have recommended restricting fluoroquinolone use to cases where no safer alternatives are available.
FDA Warnings: The U.S. FDA has issued multiple safety warnings, advising against using fluoroquinolones for uncomplicated infections where the risks outweigh the benefits.
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