Page data last changed: . Chemistry registry snapshot: . Registry refreshes and identity assessments are separate from scientific content review.
A last-line polycationic lipopeptide that targets lipid A of Gram-negative bacteria; on the WHO Essential Medicines List.
Also known as: PMB
Part of the Foundational & therapeutic peptides cluster
Overview
Polymyxin B is a cyclic lipopeptide antibiotic from Paenibacillus polymyxa, produced as a mixture of closely related components. Its cationic diaminobutyric acid residues bind the lipid A of lipopolysaccharide, permeabilizing the Gram-negative outer membrane. Approved since 1964 and on the WHO Essential Medicines List, it is used for serious Gram-negative infections and in topical combinations. This page is educational and not medical advice.
Source & context
Biological / chemical source: Soil bacterium Paenibacillus polymyxa (formerly Bacillus polymyxa)
Primary research or clinical context: Approved antibiotic for serious Gram-negative infections; also in topical products
Structure and mechanism
Polymyxin B is a cyclic heptapeptide with a tripeptide side chain bearing a fatty-acyl tail and several 2,4-diaminobutyric acid (Dab) residues. The positively charged Dab groups bind anionic lipid A, displacing stabilizing cations and dissolving into the membrane so that it leaks. It is inactive against Gram-positive bacteria.
Clinical role
Once limited by kidney and nerve toxicity, polymyxin B re-emerged as a treatment for multidrug-resistant Gram-negative infections such as those from Pseudomonas aeruginosa. It also appears in over-the-counter topical antibiotic ointments alongside bacitracin and neomycin. Systemic use requires clinical supervision.
Structure & chemistry
Molecular identity & reference confidence
Source-supported reference
Reference values are taken from the cited molecular record or curated profile. A database match is not independent laboratory verification; modifications, counter-ions, and formulations can change the measured mass.
- Molecular form
- Polymyxin B (source record; form not independently established)
- Species
- Not established by this molecular identity audit
- Termini (N / C)
- Not specified / Not specified
Average reference mass
Reference policy updated: 2026-10-05
- IUPHAR/BPS source snapshot · 2026-09-06
- PubChem molecular record · 2026-09-06
- Molecular formula
- C56H98N16O13
- Average reference mass
- ≈ 1,203.5
- Status
- Approved medicine in at least one jurisdiction (IUPHAR record)
- PubChem CID: 4868
- IUPHAR ligand: 10338
- ChEMBL: CHEMBL241797
Chemistry values: PubChem, IUPHAR/BPS Guide to Pharmacology · fetched 2026-09-06.
Clinical development snapshot
ClinicalTrials.gov lists 84 registered studies with “Polymyxin B” as an intervention (snapshot 2026-10-01). A registry footprint is not evidence of efficacy or approval.
| NCT | Title | Phase | Status | Updated |
|---|---|---|---|---|
| NCT05157113 | Evaluating a Dropless Postoperative Regimen After Cataract Surgery in a Vulnerable, County-hospital Population | Phase 4 | completed | 2026-09-24 |
| NCT05331664 | Dropless Pars Plana Vitrectomy Study | Phase 4 | completed | 2026-09-18 |
| NCT07826351 | Exploring the Combination of Intracalvariosseous and Intravenous Antibiotics for Moderate to Severe Bacterial | Not applicable | not yet recruiting | 2026-09-17 |
| NCT07788144 | EAA-Guided AN69-oXiris and PMX-HP Therapy in Septic Patients | Not applicable | enrolling by invitation | 2026-08-26 |
| NCT07759934 | ASK0912 Versus Polymyxin B for Injection in Adults With Hospital-Acquired or Ventilator-Associated Bacterial P | Phase 2 | recruiting | 2026-08-12 |
| NCT03920007 | Study of Subretinally Injected ATSN-101 Administered in Patients With Leber Congenital Amaurosis Caused by Bia | Phase 2 | active not recruiting | 2026-08-03 |
Polymyxin B — reconstitution calculator
Enter how much peptide is in the vial and how much diluent (e.g. bacteriostatic water) is added. The tool returns the resulting solution concentration — and, for any amount you type, the volume it corresponds to. This is educational arithmetic, not a dosing recommendation.
Reference form: Polymyxin B (source record; form not independently established)Average reference mass: 1,203.5 Da
Enter an amount to see the volume it corresponds to.
Educational concentration mathematics only. This tool does not recommend a dose, amount, or protocol, and nothing here is medical advice. Many peptides are not authorized by Health Canada for human use — see our reconstitution and bacteriostatic-water guides for context.
Change log
Dated observations from the data pipeline (registry flags, trial footprints, identifiers) and editorial reviews of this profile.
- Trials1 registered study added on ClinicalTrials.gov (now 84).
FAQ about Polymyxin B
What is Polymyxin B?+
Polymyxin B is a cyclic lipopeptide antibiotic from Paenibacillus polymyxa, produced as a mixture of closely related components. Its cationic diaminobutyric acid residues bind the lipid A of lipopolysaccharide, permeabilizing the Gram-negative outer membrane. Approved since 1964 and on the WHO Essential Medicines List, it is used for serious Gram-negative infections and in topical combinations. This page is educational and not medical advice.
What Canadian product status is recorded for Polymyxin B?+
Canadian product status for Polymyxin B has not been verified in this profile. No verified record here does not mean no authorization exists. Status depends on the product, formulation and use; consult Health Canada's product records.
What is the typical length of Polymyxin B?+
Polymyxin B is not a classic amino-acid chain peptide in the same sense; see the profile for classification details.
Related peptides
References & further reading
- 1.Rigatto et al. (2019). Clinical Use of Polymyxin B. Adv Exp Med Biol
- 2.Mohapatra et al. (2021). Polymyxin B accelerates the α-synuclein aggregation. Biophys Chem
- 3.Cai et al. (2015). Polymyxin B versus colistin: an update. Expert Rev Anti Infect Ther
- 4.Sharma et al. (2024). Polymyxin B Hemoperfusion in Sepsis: A Possible Silver Lining to the Dark Clouds?. Indian J Crit Care Med
- 5.Antonelli et al. (2015). Polymyxin B hemoperfusion in sepsis: growing body of evidence and occasional conflicting results. Blood Purif
- 6.Ilia et al. (2017). Polymyxin B hemoperfusion in septic shock: nothing overmuch (Meden Agan)!. J Thorac Dis
- 7.Horton et al. (1982). Polymyxin B, colistin, and sodium colistimethate. Med Clin North Am
- 8.Avedissian et al. (2019). A Review of the Clinical Pharmacokinetics of Polymyxin B. Antibiotics (Basel)
- 9.PubChem — compound summary for Polymyxin B (CID 49800004)
- 10.Wikipedia — Polymyxin B