Almost all respondents had excess and leftover medications in their homes. This may be a result of both overprescribing and poor medication adherence. In addition to the potential human health risk of nonadherence, disposal of excess medication raises concerns about their environmental impact and safety.

The use of higher doses of either colistin or polymyxin B, as well as combination with other antibiotics, may prevent emerging resistance and preserve the activity of polymyxins against A. baumannii.

We currently face a lack of new antimicrobial therapies in an era of increasingly common multidrug-resistant (MDR) bacteria. The polymyxins have become last-line treatments for patients with MDR bacterial infections. An increasing body of published literature has attempted to answer questions about dosing, pharmacology, and susceptibility testing of these drugs, yet each takes for granted purity and potency of the 2 available polymyxin products. In the case of polymyxin B, true potency may vary by as much as 40% from the content reported in prescribing information. This poor accuracy is related to quality assurance assays established in the 1940s and currently in use, which have been shown to be significantly flawed in recent investigations. This review discusses the limitations of pharmacological knowledge about polymyxin antimicrobials, the clinical impact of these limitations, and suggestions for further study of these drugs in order to optimize their use clinically.

The polymyxins-colistin and polymyxin B-are an increasingly important part of the antimicrobial arsenal given the rising rate of infections due to multidrug-resistant gram-negative bacteria. Although the drugs have available since the 1950s, only recently have pharmacokinetic and pharmacodynamic data been available to guide appropriate use of these drugs. Far more data and global clinical experience exist for colistin, available as the prodrug colistimethate sodium (CMS), compared with polymyxin B. Concerns raised about variability in the ability to achieve therapeutic drug concentrations when dosing CMS have led many clinicians to desire a more pharmacokinetically reliable product. The pharmacokinetic and pharmacodynamic advantages of polymyxin B compared with CMS are compelling, but clinical experience has not consistently corroborated these data. Prospective, comparative data evaluating both drugs in combination with other antimicrobials as well as comparing polymyxin B and CMS directly will inform optimal use of each drug. Some of these investigations are currently under way. In the meantime, based on current data, both drugs appear to be appropriate for use in the clinical setting.

Comparable rates of clinical improvement, survival to discharge, and toxicity were identified among low- and standard-dose L-AMB recipients.