Polymyxins have re-emerged in clinical practice owing to the dry
antibiotic development pipeline and worldwide increasing prevalence of
nosocomial infections caused by multidrug-resistant (MDR) Gram-negative bacteria.
Polymyxin B and
colistin (
polymyxin E) have been ultimately considered as the last-resort treatment of such
infections. Microbiological, pharmacokinetic, pharmacodynamic and clinical data available for
polymyxin B are reviewed in this paper.
Polymyxin B has rapid in vitro bactericidal activity against major MDR Gram-negative bacteria, such as Pseudomonas aeruginosa, Acinetobacter baumannii and Klebsiella pneumoniae. Acquired resistance to this agent is still rare among these pathogens. However, optimized dosage regimens are not known yet. Good clinical outcomes have been observed in the majority of the patients treated with intravenous
polymyxin B in recent studies. However, these studies failed to provide definitive conclusions due to limitations of study design and additional clinical trials are required. Although combination
therapy may be an attractive option based on some currently available in vitro data, clinical data supporting such recommendations are lacking. Since
polymyxins will be increasingly used for the treatment of
infections caused by MDR bacteria, clinical pharmacokinetic, pharmacodynamic and toxicodynamic studies underpinning the optimal use of these drugs are urgently required.