1. Polymyxin B: similarities to and differences from colistin (polymyxin E)
Andrea Kwa, Sofia K Kasiakou, Vincent H Tam, Matthew E Falagas Expert Rev Anti Infect Ther. 2007 Oct;5(5):811-21. doi: 10.1586/14787210.5.5.811.
Hospital-acquired infections due to multidrug-resistant gram-negative bacteria constitute major health problems, since the medical community is continuously running out of available effective antibiotics and no new agents are in the pipeline. Polymyxins, a group of antibacterials that were discovered during the late 1940s, represent some of the last treatment options for these infections. Only two polymyxins are available commercially, polymyxin E (colistin) and polymyxin B. Although several reviews have been published recently regarding colistin, no review has focused on the similarities and differences between polymyxin B and colistin. These two medications have many similarities with respect to mechanism of action, antimicrobial spectrum, clinical uses and toxicity. However, they also differ in several aspects, including chemical structure, formulation, potency, dosage and pharmacokinetic properties.
2. Clinical Use of Polymyxin B
Maria Helena Rigatto, Diego R Falci, Alexandre P Zavascki Adv Exp Med Biol. 2019;1145:197-218. doi: 10.1007/978-3-030-16373-0_14.
Polymyxin B is another clinically available polymyxin that has re-emerged in clinical practice to treat infections caused by multi-drug (MDR) or extensively-drug-resistant (XDR) Gram-negative bacteria (GNB). Its chemical structure is very similar to the structure of polymyxin E (colistin). However, since the latter is administered as a prodrug, there are major pharmacokinetic differences between both polymyxins that may potentially determine different clinical and microbiological outcomes. Studies addressing clinical or microbiological outcomes in patients treated with polymyxin B for MDR or XDR GNB are reviewed in this chapter.
3. Pharmacokinetics/pharmacodynamics of colistin and polymyxin B: are we there yet?
Thien B Tran, Tony Velkov, Roger L Nation, Alan Forrest, Brian T Tsuji, Phillip J Bergen, Jian Li Int J Antimicrob Agents. 2016 Dec;48(6):592-597. doi: 10.1016/j.ijantimicag.2016.09.010. Epub 2016 Oct 18.
The polymyxin antibiotics [colistin and polymyxin B (PMB)] are increasingly used as a last-line option for the treatment of infections caused by extensively drug-resistant Gram-negative bacteria. Despite having similar structures and antibacterial activity in vitro, the two clinically available polymyxins have very different pharmacological properties, as colistin (polymyxin E) is intravenously administered to patients in the form of an inactive prodrug colistin methanesulphonate (sodium). This review will discuss recent progress in the pharmacokinetics/pharmacodynamics and toxicity of colistin and PMB, the factors that affect their pharmacological profiles, and the challenges for the effective use of both polymyxins. Strategies are proposed for optimising their clinical utility based upon the recent pharmacological studies in vitro, in animals and patients. In the 'Bad Bugs, No Drugs' era, polymyxins are a critically important component of the antibiotic armamentarium against difficult-to-treat Gram-negative 'superbugs'. Rational approaches to the use of polymyxins must be pursued to increase their effectiveness and to minimise resistance and toxicity.
