Polymyxin B: A Literature Course on What the Published Studies Report

Polymyxin B is one of the older antibacterial lipopeptides still discussed in the current literature, and the published record around it is unusual: decades-old clinical use sits alongside very recent mechanistic and formulation work. This course walks through that record module by module, summarising what researchers studied and what they reported, without translating any of it into instructions.

This page is for educational purposes only and is not medical advice; consult a licensed physician about any medical question or decision. No dosing schedules appear anywhere on this page, because the verified sources summarised here do not supply them in a form that can be reported responsibly.

Module 1: What Polymyxin B Is and How It Has Been Studied

Definition and class

Polymyxin B is a cyclic cationic lipopeptide antibiotic. Structurally it consists of a cyclic heptapeptide ring, a short exocyclic tripeptide chain, and a fatty acyl tail, with several positively charged diaminobutyric acid residues. It is a fermentation product of the soil bacterium Paenibacillus polymyxa, and commercial material is a mixture of closely related congeners rather than a single molecule. Because it is a peptide antibiotic rather than a signalling peptide, it is grouped with colistin (polymyxin E) in the polymyxin class rather than with metabolic or regenerative peptides.

Why stereochemistry has been examined

The three-dimensional arrangement of the polymyxin scaffold has itself been treated as a research question. A 2022 study in ACS Infectious Diseases investigated polymyxin stereochemistry and its role in antibacterial activity and outer membrane disruption, and researchers reported that stereochemical configuration was relevant to both properties (PMID 36342383). That framing matters for a reader trying to interpret the literature: results obtained with one stereochemical variant or synthetic analogue do not automatically describe the marketed compound.

How the literature is distributed

The published work falls into four rough groups: mechanism-of-killing studies in bacteria; in vitro potentiation and synergy experiments; nanoparticle and delivery engineering; and clinical literature consisting of a review chapter, a patient study, and individual case reports. A 2019 chapter in Advances in Experimental Medicine and Biology summarised the clinical use of polymyxin B (PMID 31364080), and it functions as the orienting clinical reference for the rest of this course.

Limits of the evidence in Module 1

None of the verified sources characterise polymyxin B as a wellness, performance or anti-ageing compound, and none study it outside an antibacterial or biophysical context. Structural and origin descriptions above are background chemistry, not study findings, and readers should not treat descriptive class information as evidence of any outcome.

Module 2: Mechanism as Described in the Literature

Outer membrane disruption

The classical account is that the cationic peptide binds the lipid A component of lipopolysaccharide in the Gram-negative outer membrane and destabilises it. Recent work refined that picture. A 2025 study in Nature Microbiology reported that polymyxin B lethality required energy-dependent outer membrane disruption, indicating that killing was not explained by passive membrane binding alone (PMID 41023239). The 2022 stereochemistry study likewise linked structural configuration to measurable outer membrane disruption (PMID 36342383).

Conditions that changed measured activity

Several papers examined what modulates activity rather than what the drug does alone. Researchers reported in Antimicrobial Agents and Chemotherapy in 2020 that lysophosphatidylcholine potentiated the antibacterial activity of polymyxin B (PMID 32988824). A 2026 paper in Journal of Environmental Sciences examined benzalkonium chloride combined with polymyxin B against Pseudomonas aeruginosa and reported a synergistic antibacterial effect together with a proposed mechanism (PMID 41005913).

The molecule used as a targeting element

Because polymyxin B binds Gram-negative envelopes selectively, some groups used it as a homing moiety rather than as the killing agent. A 2021 Chemical Communications report described a polymyxin B-modified conjugated oligomer nanoparticle used for targeted identification of bacteria and for enhanced photodynamic antimicrobial therapy (PMID 34633009).

An off-target biophysical observation

Not all mechanistic work is antibacterial. A 2021 study in Biophysical Chemistry reported that polymyxin B accelerated α-synuclein aggregation in a biophysical system (PMID 34118773). This was a protein-aggregation experiment, not a disease model, and the authors' observation should not be read as a clinical finding.

Limits of the evidence in Module 2

Mechanistic experiments were performed in bacteria, in membrane systems and in purified protein preparations. Conditions such as added lysophosphatidylcholine or benzalkonium chloride are laboratory manipulations; they describe what changed activity in a dish, not what happens in a human body. Mechanism does not establish clinical benefit.

Module 3: Reported Outcomes by Study

The table below summarises what each verified study examined and what its authors reported. No effect sizes, percentages or doses are given, because the verified reference set does not support them at that level of detail.

Limits of the evidence in Module 3

Most rows above describe laboratory systems. The single patient-based entry, the 2023 study of elderly patients with carbapenem-resistant infection, was an observational clinical investigation rather than a randomised trial (PMID 37968642). Formulation work such as the 2026 nanoassembly study describes an engineered construct, not conventional polymyxin B as administered in hospitals (PMID 41780684). Nothing in this module should be read as a promise of benefit.

Module 4: Polymyxin B Side Effects: What Studies Report

Kidney-related findings

Renal toxicity is the adverse event most consistently addressed. The 2023 study in Annals of Clinical Microbiology and Antimicrobials explicitly paired efficacy with nephrotoxicity as co-primary concerns in elderly patients with carbapenem-resistant bacterial infection, indicating that renal injury was frequent enough to warrant systematic measurement in that population (PMID 37968642). The 2026 Journal of Controlled Release paper was built around the same problem: researchers reported that polymyxin B-antioxidant nanoassemblies mitigated nephrotoxicity while attenuating sepsis-induced acute lung injury, a design that presupposes nephrotoxicity as a limiting feature of the unmodified drug (PMID 41780684).

Skin hyperpigmentation

Two separate 2020 case reports documented skin hyperpigmentation associated with polymyxin B. One appeared in Case Reports in Medicine and described polymyxin B-induced skin hyperpigmentation in a single patient (PMID 33014066), and a second, in Transplant Infectious Disease, reported the same phenomenon in a transplant-setting patient (PMID 32386075). Two independent case reports establish that the event has been observed and described; they do not establish how often it occurs.

Hypersensitivity

A 2025 case report in Frontiers in Pharmacology described polymyxin B-induced anaphylactic shock in an individual patient (PMID 40635743). As with the pigmentation reports, this is a single-patient observation, and case reports are selected for being notable rather than representative.

Clinical context

The 2019 review chapter on the clinical use of polymyxin B provides the broader clinical framing within which these individual reports sit (PMID 31364080). Neurological adverse effects are widely discussed in the older polymyxin literature, but the verified sources on this page do not quantify them, so no figures are given here.

Limits of the evidence in Module 4

Case reports cannot generate incidence rates, and the clinical study cited here examined a specific elderly population with carbapenem-resistant infection rather than a general one (PMID 37968642). Absence of an adverse event from this page is not evidence that it does not occur; it reflects the boundaries of the verified reference set.

Module 5: Pharmacokinetics Where Data Exist

Polymyxin B is a large, highly charged peptide, and the pharmacological literature treats it as a parenteral agent for systemic infection and as a topical agent for surface application. The 2019 clinical use chapter is the source in this reference set that addresses clinical administration and its practical considerations (PMID 31364080).

Two general points can be drawn from the studies summarised above without citing numbers that the verified sources do not supply. First, the 2025 mechanistic work indicated that bacterial killing depended on an energy-dependent membrane process, meaning that exposure alone was not sufficient to predict lethality in that system (PMID 41023239). Second, kidney exposure is central to how the compound is engineered: the 2026 nanoassembly study set out specifically to alter the disposition-related toxicity profile and reported mitigated nephrotoxicity for the nanoassembly form (PMID 41780684).

Limits of the evidence in Module 5

No half-life, clearance, volume-of-distribution or plasma-concentration values are stated on this page, because none of the verified sources listed here provide them within the scope summarised. Readers seeking quantitative pharmacokinetics should consult primary pharmacology literature and prescribing information rather than an educational summary. Formulation-specific data, such as those from nanoassembly research, do not transfer to conventional preparations (PMID 41780684).

Module 6: Regulatory Status

Stated factually and without legal interpretation: polymyxin B sulfate is an approved pharmaceutical ingredient in the United States and many other jurisdictions. Polymyxin B for Injection is a prescription product, and polymyxin B also appears as a component of topical, ophthalmic and otic combination preparations, some of which are available without prescription in the United States. Its clinical use in hospitals is the subject of the 2019 review chapter cited throughout this course (PMID 31364080).

Separately, polymyxin B is sold by chemical suppliers as a research reagent labelled "research use only" (RUO). RUO material is not manufactured, released or labelled for administration to humans, and RUO labelling is a statement about intended laboratory use, not an approval pathway. In the United States, compounded preparations of approved drug substances are governed by sections 503A and 503B of the Federal Food, Drug, and Cosmetic Act, which distinguish patient-specific compounding by licensed pharmacies from outsourcing facility production. Polymyxin B is not a dietary supplement and is not marketed as one.

This regulatory summary is general information, is not legal advice, and does not describe the rules of any particular country, state or profession; requirements change and vary by jurisdiction.

Limits of the evidence in Module 6

Regulatory status describes what is permitted or how a product is labelled. It says nothing about efficacy, safety in any individual, or the quality of any particular material, and approval of a hospital antibacterial product does not extend to unrelated uses.

What the Studies Did Not Test

Across the verified literature summarised here, several things were never examined:

• Non-infectious uses. No verified study evaluated polymyxin B for performance, body composition, recovery, cognition or longevity.
• Healthy volunteers over time. The clinical evidence cited concerns patients with carbapenem-resistant bacterial infection, not healthy people (PMID 37968642).
• Human translation of formulation work. The nanoassembly and photodynamic nanoparticle studies described engineered constructs in laboratory settings rather than approved therapies (PMID 41780684, PMID 34633009).
• Clinical meaning of the protein-aggregation finding. The report that polymyxin B accelerated α-synuclein aggregation was a biophysical observation and was not tested as a disease outcome (PMID 34118773).
• Incidence of the reported adverse events. Hyperpigmentation and anaphylaxis were documented in individual case reports, which do not estimate frequency (PMID 33014066, PMID 40635743).
• Combination behaviour in people. Potentiation by lysophosphatidylcholine and synergy with benzalkonium chloride were in vitro findings only (PMID 32988824, PMID 41005913).

Antibacterial agents are also subject to considerations that laboratory studies rarely capture, including resistance selection, hospital stewardship and infection-specific decision-making. Those judgements belong to clinicians. This course exists to describe the published record accurately, not to guide use of any compound.

References

• Polymyxin B lethality requires energy-dependent outer membrane disruption (Nature Microbiology, 2025)
• Polymyxin Stereochemistry and Its Role in Antibacterial Activity and Outer Membrane Disruption (ACS Infectious Diseases, 2022)
• Lysophosphatidylcholine Potentiates Antibacterial Activity of Polymyxin B (Antimicrobial Agents and Chemotherapy, 2020)
• Synergistic antibacterial effect and mechanism of benzalkonium chloride and polymyxin B against Pseudomonas aeruginosa (Journal of Environmental Sciences, 2026)
• Polymyxin B-modified conjugated oligomer nanoparticle for targeted identification and enhanced photodynamic antimicrobial therapy (Chemical Communications, 2021)
• Polymyxin B-antioxidant nanoassemblies mitigate nephrotoxicity and attenuate sepsis-induced acute lung injury (Journal of Controlled Release, 2026)
• Efficacy and nephrotoxicity of polymyxin B in elderly patients with carbapenem resistant bacterial infection (Annals of Clinical Microbiology and Antimicrobials, 2023)
• Clinical Use of Polymyxin B (Advances in Experimental Medicine and Biology, 2019)
• Polymyxin B-Induced Skin Hyperpigmentation (Case Reports in Medicine, 2020)
• Polymyxin B-induced skin hyperpigmentation (Transplant Infectious Disease, 2020)
• Case Report: Polymyxin B-induced anaphylactic shock (Frontiers in Pharmacology, 2025)
• Polymyxin B accelerates the α-synuclein aggregation (Biophysical Chemistry, 2021)