Polymyxin B
**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.
Mecanismo: 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.
Dosificación por especie
- External pseudomonal infections (e.g., keratoconjunctivitis, otitis externa) · Apply topically as directed by specific product formulation · topical · As directed · Until clinical resolution · Do not use if tympanum is ruptured.
- External pseudomonal infections (e.g., keratoconjunctivitis, otitis externa) · Apply topically as directed by specific product formulation · topical · As directed · Until clinical resolution · Do not use if tympanum is ruptured.
Las dosis son una referencia clínica para médicos veterinarios. Confirme siempre con la información vigente del producto y el paciente individual.
Vías de administración
Contraindicaciones
- Ruptured tympanic membrane (tympanum)
- Systemic administration
Efectos adversos
- Nephrotoxicity (if absorbed systemically)
- Ototoxicity (potential, especially if tympanic membrane is ruptured)
- Local irritation
Interacciones farmacológicas
- Other antibacterial agents · Acts synergistically by disrupting the outer and cytoplasmic membranes, improving penetration of other agents into bacterial cells. · moderate
- Chlorhexidine · Cationic detergents potentiate the antibacterial effects of polymyxin B against Pseudomonas aeruginosa. · moderate
- EDTA · Chelating agents potentiate the antibacterial effects of polymyxin B against Pseudomonas aeruginosa. · moderate
Monitoreo
- Resolution of clinical signs (ear, eye, or skin infection)
- Tympanic membrane integrity (must be verified before otic use)
Sobredosis
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.
La referencia de fármacos de VetSheet está destinada a médicos veterinarios como apoyo a la decisión clínica; no sustituye el juicio profesional ni la información vigente del fabricante.