antibioticsbooks

Fluoroquinolones
8
Agents: ciprofloxacin, levofloxacin,
moxifloxacin, gemifloxacin
Many of the fluoroquinolones are near-ideal antibiotics:
they have broad-spectrum activity that
includes Gram-positive, Gram-negative, and atypical
organisms; display excellent oral bioavailability;
and have a relatively low incidence of adverse
effects. Unfortunately, these characteristics have
led to overprescribing and the inevitable rise in
resistance, despite recommendations to reserve
this class. In particular, although activity against
enteric Gram-negative organisms (such as E. coli
and Klebsiella) historically has been excellent, in
certain geographical regions or patient populations
these drugs have lost much of their potency.
The newer drugs (moxifloxacin, gemifloxacin) gain
increasing Gram-positive (mostly pneumococcal)
activity at the expense of some Gram-negative
(mostly Pseudomonas) activity. Significant differences
among the agents are in bold.
Mechanism of Action
Fluoroquinolones inhibit DNA topoisomerases,
enzymes that are involved in winding and unwinding
the DNA; the action of the fluoroquinolones can
lead to breaks in the DNA and death of the cell.