Polymyxin B / Colistin
Polymyxin B and colistin are distinct polymyxin antibiotics. Colistimethate sodium is a precursor formulation associated with colistin, not a synonym for polymyxin B.
At a glance
- Evidence stage
- Approved use
- Regulatory status
- US-approved polymyxin products have specific serious-infection indications. FDA lists the cited COLY-MYCIN M brand discontinued; that does not describe every generic product.
- Research context
- Polymyxin B and colistin are distinct polymyxin antibiotics. Colistimethate sodium is a precursor formulation associated with colistin, not a synonym for polymyxin B.
What this is
- Polymyxin B and colistin are distinct polymyxin antibiotics. Colistimethate sodium is a precursor formulation associated with colistin, not a synonym for polymyxin B.
What this isn't
- A recommendation to use, prepare, combine, or administer a product
- Evidence that a related molecule or a differently formulated product has the same effects
Key terms
Polymyxin B and colistin are distinct polymyxin antibiotics. Colistimethate sodium is a precursor formulation associated with colistin, not a synonym for polymyxin B.
Polymyxins act against susceptible Gram-negative bacteria by disrupting bacterial membranes. Colistin and polymyxin B differ in formulation and pharmacology, and colistimethate is converted to active colistin. These distinctions matter when interpreting antibacterial exposure and kidney effects. The group should not be represented as a single interchangeable antimicrobial peptide. Product label.
Evidence limits
How to read the evidence
The FDA record marks the COLY-MYCIN M brand discontinued. FDA application record. That status cannot establish availability of other colistimethate or polymyxin-B products. Infection-site penetration, susceptibility results, alternative antibiotics, renal function, and the exact formulation remain necessary context for interpreting this literature. Product-specific scope.
Sources appraised 2026-10-28. Educational information; not medical advice. Study findings apply to the populations, preparations and outcomes described.
External sources and citations
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