Bacterial Gyrase Inhibitors (Fluoroquinolones)

Overview
  • Bacterial Gyrase Inhibitors, also known as "Fluoroquinolones", are a novel class of antibacterials with a common structure and a shared mechanism of action. These drugs produce relatively few adverse effects, have a broad range, and are absorbed well orally. Their names are easily identified by the -floxacin suffix.
Mechanism of Action
  • Winding and unwinding of the DNA double helix is a critical process required for DNA replication and RNA transcription. DNA Gyrases are a class of enzymes which assist in this winding and unwinding process by nicking one of the DNA strands, rotating the helix around the un-nicked strand, and resealing the helix. Fluoroquinolones function by potently and selectively inhibiting bacterial DNA gyrases and in doing so inhibit bacterial growth and protein production.
Resistance
  • Resistance to fluoroquinolones is spreading and renders organisms impervious to every member of the class. Resistance is mediated by mutations in DNA gyrase such that the antibiotic can no longer bind. Additionally, some gram negative bacteria actively efflux the drugs or reduce the permeability the drugs through the outer membrane.
Adverse Effects
  • GI System: Some patients report GI irritation such as vomiting and diarrhea
  • CNS: May induce headache in some
  • Cartilage: The drug has been shown to damage growing cartilage in animals and is thus avoided in pregnant women and children
Member Drugs
  • Ciprofloxacin
  • Ofloxacin
  • Levofloxacin
  • Moxifloxacin
  • Trovafloxacin: May display some hepatotoxicity