Polymyxin B

Polymyxin B In Dogs & Cats: Uses, Dosage and Side Effects

Overview

• Concentration-dependent disruption of the outer membrane of Gram-negative bacteria through its action as a cationic surface-acting agent.

Uses of Polymyxin B

• Effective against Gram-negative organisms; Gram-positives usually resistant.
• Particularly effective in the treatment of external pseudomonal infections, e.g. keratoconjunctivitis, and otitis external.
• Polymyxins are too toxic for systemic use and because of their strongly basic nature are not absorbed from the GI tract.

Dose of Polymyxin B in Dogs and Cats

Dogs, Cats:

• Skin: apply a few drops and rub in well q12h.
• Otic: clean the ear and apply a few drops into the affected ear q12h.
• Ophthalmic: apply ointment q6–8h.

Side Effects of Polymyxin B in Dogs and Cats

• Should not be used systemically as is nephrotoxic. Potentially ototoxic.

Contraindications of Polymyxin B in Dogs and Cats

• Do not use if the tympanum is ruptured.

Some Notes:

• Acts synergistically with some other antibacterial agents as it disrupts the outer and cytoplasmic membranes, thus improving penetration of other agents into
  bacterial cells.
• Cationic detergents (e.g. chlorhexidine) and chelating agents (e.g. EDTA) potentiate the antibacterial effects of polymyxin B against Pseudomonas aeruginosa.