antibioticsbooks

Polymyxins
19
Agents: colistin (colistimethate sodium),
polymyxin B
Polymyxins are an older class of antibiotics that
had nearly vanished from systemic use years
ago in favor of the “safer” aminoglycosides.
Unfortunately, the continuous evolution of bacterial
resistance has reinvigorated the use of colistin
and polymyxin B in the treatment of resistant
Gram-negative infections. This is problematic
because these drugs have not been evaluated with
the rigor of the modern drug approval process,
and pharmacokinetic and efficacy data on their
use are limited. However, they have been found to
be useful in the treatment of infections caused by
highly resistant Gram-negative organisms such
as Acinetobacter baumannii and carbapenemresistant
Enterobacteriaceae (CRE).
Mechanism of Action
Polymyxins bind to the outer membrane of Gramnegative
bacteria, leading to disruption of membrane
stability and leakage of cellular contents.