Polymyxin Side Effects: What Studies Report

Evidence tier: Established. Polymyxin B is a prescription antibacterial medicine used in hospital settings, most often against multidrug-resistant Gram-negative organisms. Because it has been in clinical use for decades, its safety profile has been described in retrospective cohorts, case reports, pharmacokinetic analyses and laboratory models rather than only in early exploratory work. This page summarises what those published sources reported about adverse effects. This page is for educational purposes only and is not medical advice; consult a licensed physician about any medication, symptom or laboratory result.

What the literature covers

Polymyxin B is a polypeptide antibacterial agent that acts on the outer membrane of Gram-negative bacteria. The same physicochemical properties that make it active also underlie the toxicity signals most often discussed in the literature: accumulation in renal tubular cells, effects on pigment-producing cells in skin, and occasional disturbances of renal electrolyte handling. The verified sources summarised here fall into four groups — clinical cohorts describing kidney injury, case reports describing skin and electrolyte findings, laboratory and formulation studies exploring mechanisms and mitigation, and a veterinary observational report.

Kidney Injury: What Studies Report

Nephrotoxicity is the adverse effect most consistently examined in the polymyxin B literature. A retrospective study of patients treated for carbapenem-resistant Gram-negative bacterial infections assessed polymyxin B-associated nephrotoxicity and searched for clinical predictors of who developed it (PMID 35571125). The researchers framed kidney injury as a common, dose- and exposure-related complication rather than an idiosyncratic reaction, and analysed baseline patient characteristics and concurrent therapy as candidate risk factors (PMID 35571125).

A second retrospective analysis looked specifically at renal transplant recipients, a group whose kidney function is already fragile, and assessed both nephrotoxicity and treatment efficacy when polymyxin B was used (PMID 35115795). The study reported that nephrotoxicity assessment in transplant patients is complicated by graft-related changes in creatinine, and the authors framed the analysis as a balance between the antibacterial benefit and renal risk in that population (PMID 35115795).

Why exposure varies between patients

An individual participant data meta-analysis pooled pharmacokinetic datasets to build a population pharmacokinetic description of polymyxin B across patients (PMID 42229684). Work of this kind is relevant to the safety discussion because the researchers characterised how drug exposure differs between individuals receiving similar regimens — variability that clinical papers have linked to the likelihood of renal adverse effects (PMID 42229684). No dosing figures are reproduced here; regimen decisions belong to prescribing clinicians and to product labelling.

Mechanistic Work on Renal Toxicity: What Studies Report

Laboratory research has tried to explain why renal tubular cells are vulnerable. One study reported that polymyxin B exerted nephrotoxic effects through inhibition of the Nrf2/NQO1 pathway, a signalling route that normally supports the cell's antioxidant response (PMID 36992629). In that model, blunting of the antioxidant response was described as a contributor to oxidative injury in kidney cells (PMID 36992629).

Building on that mechanistic theme, a formulation study described polymyxin B–antioxidant nanoassemblies and reported that the approach mitigated nephrotoxicity while attenuating sepsis-induced acute lung injury in preclinical testing (PMID 41780684). These are laboratory and animal findings about an experimental delivery format, not a description of any marketed product, and the researchers did not report human outcomes (PMID 41780684).

Skin Hyperpigmentation: What Studies Report

Darkening of the skin during polymyxin B therapy has been documented in the case report literature. A transplant infectious disease case report described polymyxin B-induced skin hyperpigmentation in a treated patient (PMID 32386075). A separate case report published the same year also described polymyxin B-induced skin hyperpigmentation, adding to the small series of published observations (PMID 33014066).

Case reports establish that an event has occurred and has been attributed to a drug by treating clinicians; they cannot establish how often it happens, who is most susceptible, or how completely it resolves. Both reports were single-patient descriptions, so the literature summarised here supports recognition of the phenomenon rather than any estimate of incidence (PMID 32386075, PMID 33014066).

Bartter-like Syndrome and Electrolyte Disturbance: What Studies Report

Two case reports describe an unusual renal tubular presentation. A BMJ Case Reports description reported polymyxin B-induced Bartter syndrome, a pattern of renal salt and potassium wasting, in a patient receiving the drug (PMID 38702070). A further report characterised polymyxin B-induced Bartter-like syndrome explicitly as an unusual adverse effect of therapy (PMID 39649859).

Taken together, these two publications indicate that tubular dysfunction from polymyxin B can present as an electrolyte-wasting syndrome rather than only as a rise in creatinine (PMID 38702070, PMID 39649859). Again, the case-report format means frequency is unknown from these sources.

Animal Observations: What Studies Report

Veterinary literature contributes a separate observational angle. A preliminary investigation examined side effects of polymyxin B administration in hospitalised horses, where the drug is used for its endotoxin-binding properties (PMID 37237756). The study was explicitly described by its authors as preliminary, and equine findings cannot be transferred to humans; species differ in renal handling, comorbidity profile and monitoring practice (PMID 37237756).

Polymyxin B Outside Systemic Dosing: Hemoperfusion Devices

Polymyxin B also appears in critical care as an immobilised ligand on extracorporeal cartridges rather than as a drug circulating in the bloodstream. A review of hemoperfusion described the technical aspects and state of the art of blood-purification cartridges, including sorbent designs used in sepsis care (PMID 35549999). The safety considerations for a device that binds endotoxin outside the body are not the same as those for systemic administration, and the review addressed technical and procedural aspects of hemoperfusion rather than systemic drug toxicity (PMID 35549999). Readers encountering the term "polymyxin B hemoperfusion" are therefore reading about a distinct clinical modality.

What the Verified Literature Here Does Not Cover

Several adverse effects commonly associated with polymyxins in clinical teaching are not represented in the verified source set used for this page. Stated plainly as an absence:

• Neurotoxicity — none of the sources cited here reported neurological adverse events such as paraesthesia, dizziness or neuromuscular blockade, so no claim about their frequency or severity is made on this page.
• Hypersensitivity and infusion reactions — not described in the cited sources.
• Comparative safety versus colistin (polymyxin E) — no head-to-head comparison appears in the verified set.
• Inhaled, intrathecal or topical routes — the cited clinical papers concerned systemic use in hospitalised patients and do not support statements about other routes.
• Pregnancy, paediatric and long-term outcome data — absent from the sources cited here.

Absence from this page's source list is not evidence of absence in the wider medical literature; it simply means those topics were outside the verified references summarised above.

How to Read This Evidence

The evidence types collected here carry different weight. Retrospective cohorts describing nephrotoxicity and its predictors can estimate how often kidney injury occurred in a defined patient group, but they cannot prove causation and are influenced by how kidney injury was defined (PMID 35571125). Case reports of hyperpigmentation and Bartter-like syndrome document real, clinician-attributed events without frequency information (PMID 33014066, PMID 39649859). Laboratory studies on the Nrf2/NQO1 antioxidant pathway describe biological plausibility rather than clinical outcomes (PMID 36992629). Pharmacokinetic pooling helps explain why two patients on comparable regimens may experience different exposures (PMID 42229684).

Polymyxin B is used under medical supervision in inpatient settings, and decisions about whether it is appropriate, how it is administered and how kidney function is followed are made by treating clinicians using approved product information. Nothing on this page describes preparation, administration or dose selection.

Regulatory and Naming Notes

Polymyxin B is a non-proprietary drug name. Any brand name that a reader encounters for a polymyxin-containing product is a trademark of its owner, and PeptideU is not affiliated with or endorsed by any manufacturer, rights holder or healthcare institution. PeptideU is an educational publisher that summarises published literature; it sells nothing and makes no representation about the availability, labelling or approved indications of any product in any jurisdiction. Product labelling and regulatory status vary by country, and prescribing information is the authoritative source for clinicians.

References

• Polymyxin B-Associated Nephrotoxicity and Its Predictors: A Retrospective Study in Carbapenem-Resistant Gram-Negative Bacterial Infections (Frontiers in Pharmacology, 2022)
• Nephrotoxicity and Efficacy Assessment of Polymyxin B Use in Renal Transplant Patients (Infection and Drug Resistance, 2022)
• Polymyxin B-induced skin hyperpigmentation (Transplant Infectious Disease, 2020)
• Polymyxin B-Induced Skin Hyperpigmentation (Case Reports in Medicine, 2020)
• Polymyxin B-induced Bartter syndrome (BMJ Case Reports, 2024)
• Polymyxin-B induced Bartter-like syndrome: an unusual adverse effect (Annals of Medicine and Surgery, 2024)
• Polymyxin B exerts nephrotoxicity effects via inhibition of the Nrf2/NQO1 pathway-mediated antioxidant response (Journal of Biochemical and Molecular Toxicology, 2023)
• Polymyxin B-antioxidant nanoassemblies mitigate nephrotoxicity and attenuate sepsis-induced acute lung injury (Journal of Controlled Release, 2026)
• Population pharmacokinetics of polymyxin B: an individual participant data meta-analysis (Clinical Microbiology and Infection, 2026)
• Preliminary Investigation of Side Effects of Polymyxin B Administration in Hospitalized Horses (Antibiotics, 2023)
• Hemoperfusion: technical aspects and state of the art (Critical Care, 2022)