Fluoroquinolones

Quinolones are synthetic fluorinated analogs of nalidixic acid, that nucleic acid synthesis. Ofloxacin and ciprofloxacin inhibit gram-negative cocci and bacilli, including Enterobacteriaceae, Pseudomonas, Neisseria, Haemophilus, and Campylobacter. Many staphylococci also are sensitive these drugs. Intracellular pathogens such as Legionella, Chlamydia, M tuberculosis and M avium complex, are inhibited by fluoroquinolones.

Pharmacokinetics: After oral administration, the fluoroquinolones are well absorbed and distributed widely in body fluids and tissues. Oral absorption is impaired by divalent cations, including those in antacids. The fluoroquinolones are excreted mainly by tubular secretion and by glomerular filtration. All fluoroquinolones accumulate in renal failure.

Clinical Uses: Fluoroquinolones are effective in urinary tract infections even when caused by multidrug-resistant bacteria, eg, Pseudomonas. Norfloxacin 400 mg, ciprofloxacin 500 mg, and ofloxacin 400 mg given orally twice daily and all are effective. These agents are also effective for bacterial diarrhea caused by Shigella, Salmonella, toxigenic E coli, or Campylobacter. Fluoroquinolones (except norfloxacin, which does not achieve adequate systemic concentrations) have been employed in infections of soft tissues, bones, and joints and in intra- abdominal and respiratory tract infections, including those caused by multidrug-resistant organisms such as Pseudomonas and Enterobacter. Ciprofloxacin and ofloxacin are effective for gonococcal infection, including disseminated disease, and ofloxacin is effective for chlamydial urethritis or cervicitis.

Adverse Effects: The most common effects are nausea, vomiting, and diarrhea. Concomitant administration of theophylline and quinolones can lead to elevated levels of theophylline with the risk of toxic effects, especially seizures. Fluoroquinolones may damage growing cartilage and cause an arthropathy. Thus, they are not routinely recommended for use in patients under 18 years of age. Since fluoroquinolones are excreted in breast milk, they are contraindicated for nursing mothers.