Polymyxin B

Summary

Polymyxin B is a cyclic cationic lipopeptide antibiotic derived from Bacillus polymyxa, used primarily as a last-resort treatment for multidrug-resistant (MDR) Gram-negative bacterial infections, including those caused by Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae. It is also used topically in combination products for skin and eye infections.

Mechanism of Action

Binds to lipopolysaccharide (LPS) and phospholipids in the outer membrane of Gram-negative bacteria, disrupting membrane integrity and causing increased permeability, leakage of cellular contents, and bacterial cell death. Also neutralizes endotoxin (LPS).

Routes of Administration

Goals & Uses

• Topical skin/eye infection treatmentAntibacterialHigh
• Treatment of MDR Gram-negative infectionsAntimicrobialModerate
• Treatment of Pseudomonas aeruginosa infectionsAntibacterial TherapyModerate
• Endotoxin neutralizationImmunomodulatoryLow
• Treatment of Acinetobacter baumannii infectionsAntibacterialModerate

Contraindications

• Concurrent use of other nephrotoxic agents (systemic)Drug InteractionHigh
• Known hypersensitivity to polymyxinsAllergyHigh
• Severe renal impairment (systemic use)Organ ImpairmentHigh
• Concurrent use of neuromuscular blocking agentsDrug InteractionHigh

Adverse Effects

• Hypersensitivity reactionsImmunologicUncommon
• NeurotoxicityNeurologicalCommon
• Injection site pain/phlebitisLocalCommon
• Electrolyte disturbancesMetabolicUncommon
• SuperinfectionInfectiousUncommon
• NephrotoxicityRenalCommon

Drug Interactions

• AminoglycosidesHigh
• VancomycinModerate
• NSAIDsModerateMay increase renal risk in susceptible patients
• Neuromuscular blocking agents (e.g., vecuronium, succinylcholine)High
• Loop diuretics (e.g., furosemide)Moderate

Population Constraints

• PregnancyReproductive SafetyRelative
• Renal impairmentOrgan ImpairmentRelative
• Pediatric patientsAgeRelative
• Myasthenia gravisNeuromuscular DiseaseRelative
• Elderly patientsAgeRelative

Regulatory Status

• European UnionApprovedApproved: Severe infections due to susceptible Gram-negative bacteria, Topical/ophthalmic infections in combination productsApproved in multiple EU member states; use guided by susceptibility testing; considered last-resort for MDR pathogens
• United StatesApprovedApproved: Serious infections caused by susceptible strains of Pseudomonas aeruginosa, Meningeal infections caused by susceptible Haemophilus influenzae, Bacteremia caused by susceptible Escherichia coli, Urinary tract infections caused by susceptible Pseudomonas aeruginosa and Klebsiella pneumoniae, Ophthalmic infections (combination products)FDA-approved; systemic use reserved for serious MDR Gram-negative infections; numerous OTC topical combination products approved
• United KingdomApprovedApproved: Serious Gram-negative infections caused by susceptible organisms, Topical combination antibiotic productsAvailable in the UK; systemic use primarily as last-resort therapy for MDR infections; MHRA-regulated

FDA-approved for systemic use (intravenous and intramuscular) and ophthalmic use. Topical combination products (e.g., with neomycin, bacitracin) are OTC-available. Systemic use is limited by significant nephrotoxicity and neurotoxicity. No established therapeutic drug monitoring (TDM) standard widely adopted.

Evidence & Sources

No sources recorded yet.