A Pharmacokinetic Study of Polymyxin B in Healthy Subjects and Subjects With Renal Insufficiency

Polymyxin B acts against gram-negative bacteria (GNB) only, via three known mechanisms of action: First, polymyxin B can electrostatically interact with the outer membranes of GNB to compete against and displace calcium and magnesium divalent cations from membrane lipids, thereby disrupting lipopolysaccharide (LPS) molecules on the outer membrane and triggering their release. This leads to changes in the permeability of the bacterial membrane and subsequently causes cell content leakage, cell lysis, and death. Second, polymyxin B can act as a surfactant, as it is amphipathic and contains both lipophilic and lipophobic groups; this allows it to penetrate cell membranes, interact with the phospholipids within, and rapidly disrupt membranes to kill bacteria. Third, polymyxin B can bind to the lipid A portion of bacterial endotoxin or LPS molecules, thus neutralizing their toxicity.