Antimicrobial
Colistin (polymyxin E)
A last-resort lipopeptide antibiotic kept for multidrug-resistant Gram-negative infections, at the cost of kidney toxicity.
What it is
Colistin, or polymyxin E, is a cyclic lipopeptide antibiotic from the 1950s that was largely abandoned because of kidney toxicity and then brought back as a last resort for multidrug-resistant Gram-negative bacteria. It is given as colistimethate sodium, an inactive prodrug that converts to colistin in the body. It is a hospital medicine.
How it works
- 1
Binds the lipid A portion of lipopolysaccharide in the outer membrane.
- 2
Displaces magnesium and calcium ions, destabilising the membrane.
- 3
Increases membrane permeability, which kills the bacterium and releases endotoxin.
- 4
The prodrug colistimethate must be hydrolysed in the body to become active.
- 5
Intrinsic resistance occurs in some species, including Proteus and Serratia.
What it's studied for
Reported and studied effects
- Microbiological activity against many carbapenem-resistant organisms
- Nephrotoxicity in a substantial minority of treated patients
- Neurotoxicity, including paraesthesia and neuromuscular weakness
- Debate continues over whether combination therapy improves survival
Research protocol notes
Research context onlyResearch context only - a hospital antibiotic of last resort. Colistimethate is dosed in international units, commonly a loading dose around 9 million IU followed by maintenance doses adjusted for kidney function, with nebulised regimens used in some centres; modern trials have compared colistin combinations against other agents in resistant infection, with mortality as the endpoint.
These figures are described so you can understand what researchers did. They are not a dose, a schedule, or a suggestion — and they are not a substitute for a doctor.
Possible side effects and contraindications
Safety profile
Possible side effects
- Acute kidney injury
- Neurotoxicity, paraesthesia and dizziness
- Neuromuscular blockade, rarely apnoea
- Bronchospasm with nebulised use
- Rash
- Nausea
Contraindications and cautions
- Prior hypersensitivity
- Myasthenia gravis
- Kidney impairment requires dose reduction
- Avoid with other nephrotoxic or neuromuscular-blocking drugs where possible
A side-effect list is never complete, and these are not the only situations that warrant caution. Anything unexpected, or anything you are unsure about, should be discussed with a doctor before use.
Evidence assessment
Approved in an era before modern trial standards; most contemporary data are observational or small randomised comparisons driven by resistance, not placebo-controlled efficacy trials.
References
- 01European Medicines Agency - colistin product information and assessment report
- 02Tsuji et al., International consensus guidelines for the optimal use of polymyxins, Pharmacotherapy 2019
References link to published literature, regulator pages or literature indexes. Where a link points to a search, it collects the peer-reviewed work on that molecule rather than a single study.
Related
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Other entries in Antimicrobial.
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Dalbavancin
A long-acting lipoglycopeptide that treats serious skin infections with one or two doses instead of a week of infusions.
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Teicoplanin
A long-acting glycopeptide antibiotic used in Europe for serious Gram-positive infections, with once-daily dosing.