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Polymyxin E — a last-resort agent whose plasmid-borne mcr-1 resistance gene raised global alarm.
Also known as: polymyxin E · colistimethate (prodrug)
Part of the Foundational & therapeutic peptides cluster
Overview
Colistin, also called polymyxin E, is a cyclic lipopeptide antibiotic from Paenibacillus species and a close relative of polymyxin B. It displaces divalent cations from lipopolysaccharide phosphate groups, breaking down the Gram-negative outer membrane. Classified by the WHO as critically important and reserved as a last-resort drug, its usefulness is threatened by the mobile mcr-1 resistance gene. This page is educational and not medical advice.
Source & context
Biological / chemical source: Bacteria of the genus Paenibacillus (Paenibacillus polymyxa)
Primary research or clinical context: Last-resort approved antibiotic for multidrug-resistant Gram-negative infections
How it works
Like polymyxin B, colistin is a polycationic cyclic lipopeptide rich in diaminobutyric acid. It competitively displaces Ca2+ and Mg2+ that bridge neighboring lipopolysaccharide molecules, destabilizing the outer membrane and causing leakage and death of Gram-negative bacteria. It is administered as the less-toxic prodrug colistimethate sodium.
Resistance concern
Discovered in 1947, colistin was sidelined by toxicity, then revived against carbapenem-resistant organisms. The 2015 discovery of the plasmid-borne mcr-1 gene, which spreads colistin resistance between bacteria, made stewardship of this last-resort drug a major public-health topic.
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
- Colistin (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 · 2026-10-01
- PubChem molecular record · 2026-10-01
- Molecular formula
- C52H98N16O13
- Average reference mass
- ≈ 1,155.4
- Status
- Approved medicine in at least one jurisdiction (IUPHAR record)
- PubChem CID: 5311054
- IUPHAR ligand: 10794
- ChEMBL: CHEMBL499783
- CAS RN: 1066-17-7
- UNII: Z67X93HJG1
Chemistry values: PubChem, IUPHAR/BPS Guide to Pharmacology · fetched 2026-10-01.
Clinical development snapshot
ClinicalTrials.gov lists 122 registered studies with “Colistin” as an intervention (snapshot 2026-10-01). A registry footprint is not evidence of efficacy or approval.
| NCT | Title | Phase | Status | Updated |
|---|---|---|---|---|
| NCT06488794 | Nebulised Colistimethate Sodium to Prevent Pediatric Ventilator-associated Pneumonia | Phase 3 | not yet recruiting | 2026-09-30 |
| NCT06087536 | A Clinical Trial to Assess the Safety and PK of OMN6 in HABP or VABP Caused by Acinetobacter Baumannii Complex | Phase 2 | recruiting | 2026-09-28 |
| NCT06819462 | Inhaled Colistin to Prevent Ventilator-Associated Pneumonia in Patients With Acute Brain Injury | Not applicable | recruiting | 2026-09-15 |
| NCT07512596 | Study on the Safety and Efficacy of Polymyxin E2 Methanesulfonate for Injection in the Treatment of Hospital-A | Phase 2 | recruiting | 2026-09-04 |
| NCT07082465 | Epidemiology of Antimicrobial-use and Antimicrobial-resistant Infections in Four Hospitals in Thailand | — | active not recruiting | 2026-08-14 |
| NCT07694700 | Colistin and Meropenem Versus Amikacin and Meropenem for MDR Gram Negative Bacteria Regarding Efficacy and Saf | Phase 4 | active not recruiting | 2026-07-14 |
Colistin — 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: Colistin (source record; form not independently established)Average reference mass: 1,155.4 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.
FAQ about Colistin
What is Colistin?+
Colistin, also called polymyxin E, is a cyclic lipopeptide antibiotic from Paenibacillus species and a close relative of polymyxin B. It displaces divalent cations from lipopolysaccharide phosphate groups, breaking down the Gram-negative outer membrane. Classified by the WHO as critically important and reserved as a last-resort drug, its usefulness is threatened by the mobile mcr-1 resistance gene. This page is educational and not medical advice.
What Canadian product status is recorded for Colistin?+
Canadian product status for Colistin 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 Colistin?+
Colistin is not a classic amino-acid chain peptide in the same sense; see the profile for classification details.
Related peptides
References & further reading
- 1.El-Sayed Ahmed et al. (2020). Colistin and its role in the Era of antibiotic resistance: an extended review (2000-2019). Emerg Microbes Infect
- 2.Krishnakumar et al. (2023). Colistin (Polymyxin E) Use in Abdominal Solid Organ Transplant Recipients. J Pharm Pract
- 3.Horton et al. (1982). Polymyxin B, colistin, and sodium colistimethate. Med Clin North Am
- 4.Cai et al. (2015). Polymyxin B versus colistin: an update. Expert Rev Anti Infect Ther
- 5.Ballı et al. (2024). Battle of polymyxin induced nephrotoxicity: Polymyxin B versus colistin. Int J Antimicrob Agents
- 6.Kwa et al. (2007). Polymyxin B: similarities to and differences from colistin (polymyxin E). Expert Rev Anti Infect Ther
- 7.Nadeem et al. (2026). Intraventricular colistin for multidrug-resistant ventriculitis: the final therapeutic option?. Neurosurg Rev
- 8.Tran et al. (2016). Pharmacokinetics/pharmacodynamics of colistin and polymyxin B: are we there yet?. Int J Antimicrob Agents
- 9.PubChem — compound summary for Colistin (CID 5311054)
- 10.Wikipedia — Colistin