Quinolones are broad-spectrum antibiotics derived from nalidixic acid that are effective against urinary tract infections, bacterial prostatitis, bacterial diarrhea, bronchitis, and gonorrhea. They work by destroying bacterial DNA components called gyrase and topoisomerase IV, enzymes that are essential for cell replication.

The first generation of quinolones arose from the discovery of nalidixic acid in the 1960s and the development of norfloxacin, a fluoridated quinolone compound, in 1986. These early drugs had poor distribution throughout the body and were used primarily for urinary tract infections. Since then, more effective quinolones have been developed, and there are now nine varieties available in the United States.

Fluoroquinolones are often prescribed because their relatively long half-lives (the time it takes for the drug to leave the body) allow them to be administered only once or twice a day. They also have a relatively low incidence of serious side effects, although they are not completely without risks: Caffeine, nonsteroidal anti- inflammatory drugs, and corticosteroids enhance fluoroquinolones’ toxicity, while antacids, warfarin, antiviral agents, and other medications can interact dangerously with them. As with other types of antibiotics, resistance to quinolones can evolve quickly, and the drugs have been rendered ineffective against several pathogens around the world. Distribution of the drugs through widespread veterinary and livestock use, especially in Europe, has been implicated.

ADDITIONAL FACTS

  1. In 2008, the Food and Drug Administration requested that manufacturers place a black box warning on fluoroquinolone medications describing their increased risk of tendinitis and tendon rupture.
  2. Quercetin, an antioxidant vitamin occasionally used as a dietary supplement, competitively binds to DNA gyrase and may make quinolones less effective. But the effect on the drugs of foods that contain high levels of quercetin, such as apples and garlic, is not clear.
  3. Quinolones are usually administered orally but can also be given intravenously or applied topically for certain types of infections.