Polymyxin B
Also known as: Surolan · Polyfax · Polymyxin B sulfate
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| External pseudomonal infections (e.g., keratoconjunctivitis, otitis externa) | Apply topically as directed by specific product formulation | topical | As directed | Until clinical resolution | 🌍 EU |
- External pseudomonal infections (e.g., keratoconjunctivitis, otitis externa): Do not use if tympanum is ruptured.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| External pseudomonal infections (e.g., keratoconjunctivitis, otitis externa) | Apply topically as directed by specific product formulation | topical | As directed | Until clinical resolution | 🌍 EU |
- External pseudomonal infections (e.g., keratoconjunctivitis, otitis externa): Do not use if tympanum is ruptured.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Polymyxin B is a polypeptide antibiotic primarily effective against Gram-negative organisms, particularly Pseudomonas aeruginosa. Gram-positive bacteria are usually resistant.
Clinical Warning: Polymyxins are highly nephrotoxic and are considered too toxic for systemic use. They are restricted to topical, ophthalmic, and otic applications. Because of their strongly basic nature, they are not absorbed from the gastrointestinal tract.
Mechanism of action
Acts as a cationic surface-acting agent → binds to the bacterial cell membrane → causes concentration-dependent disruption of the outer membrane of Gram-negative bacteria → leakage of intracellular contents and cell death.
Safety & warnings
Contraindications
- Ruptured tympanic membrane (tympanum)
- Systemic administration
Adverse effects
- Nephrotoxicity (if absorbed systemically)
- Ototoxicity (potential, especially if tympanic membrane is ruptured)
- Local irritation
Precautions
Do not use systemically as it is highly nephrotoxic. Otic use: Ensure the tympanic membrane is intact before application to prevent ototoxicity.
Drug interactions
Acts synergistically by disrupting the outer and cytoplasmic membranes, improving penetration of other agents into bacterial cells.
Cationic detergents potentiate the antibacterial effects of polymyxin B against Pseudomonas aeruginosa.
Chelating agents potentiate the antibacterial effects of polymyxin B against Pseudomonas aeruginosa.
Monitoring
- Resolution of clinical signs (ear, eye, or skin infection)
- Tympanic membrane integrity (must be verified before otic use)
Pharmacokinetics
Absorption
Not absorbed from the GI tract due to its strongly basic nature. Minimal systemic absorption from intact skin or mucous membranes.
Distribution
Acts locally at the site of application.
Metabolism
Not specified for topical use.
Elimination
Not specified for topical use.
Overdose
Systemic absorption (e.g., from ingestion of large amounts or application to extensive deep wounds) can lead to severe nephrotoxicity and neurotoxicity/ototoxicity. Treatment is supportive.
Available products
Formulations
- Topical suspension (combined with miconazole and prednisolone)
- Topical ointment (combined with bacitracin)
Veterinary
- Surolan (5,500 IU polymyxin/ml suspension combined with miconazole and prednisolone)
Human-labeled
- Polyfax (10,000 IU polymyxin/g ointment combined with bacitracin)
Regulatory status
Available in various topical veterinary combinations.
POM-V classification.
POM-V, POM classification.
No regulatory data for: 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Normal precautions should be observed. Store at room temperature unless otherwise directed by the specific product label.
Client information
Apply exactly as directed by your veterinarian.
Important: Do not use in the ears if you suspect your pet's eardrum is ruptured.
Stop use and contact your vet immediately if your pet shows signs of hearing loss, head tilt, loss of balance, or worsening redness/irritation at the application site. Wash hands after applying.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.